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Carbohydrate Polymers 140 (2016) 314–341

Contents lists available at ScienceDirect

Carbohydrate Polymers

j ourna l ho me pa g e: www.elsev ier .com/ locate /carbpol

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pplication of carbohydrate polymers as corrosion inhibitorsor metal substrates in different media: A review

aviour A. Umorena,∗, Ubong M. Eduokb

Center of Research Excellence in Corrosion, Research Institute, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi ArabiaDepartment of Chemistry, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia

r t i c l e i n f o

rticle history:eceived 19 September 2015eceived in revised form1 December 2015ccepted 15 December 2015vailable online 19 December 2015

eywords:arbohydrate polymersreen inhibitorsolysaccharidesorrosionetal substrates

orrosion inhibition

a b s t r a c t

Naturally occurring polysaccharides are biopolymers existing as products of biochemical processes inliving systems. A wide variety of them have been employed for various material applications; as binders,coatings, drug delivery, corrosion inhibitors etc. This review describes the application of some green andbenign carbohydrate biopolymers and their derivatives for inhibition of metal corrosion. Their modesand mechanisms of protection have also been described as directly related to their macromolecularweights, chemical composition and their unique molecular and electronic structures. For instance, cel-lulose and chitosan possess free amine and hydroxyl groups capable of metal ion chelation and theirlone pairs of electrons are readily utilized for coordinate bonding at the metal/solution interface. Someof the carbohydrate polymers reviewed in this work are either pure or modified forms; their grafted sys-tems and nanoparticle composites with multitude potentials for metal protection applications have alsobeen highlighted. Few inhibitors grafted to introduce more compact structures with polar groups capableof increasing the total energy of the surface have also been mentioned. Exudate gums, carboxymethyland hydroxyethyl cellulose, starch, pectin and pectates, substituted/modified chitosans, carrageenan,
dextrin/cyclodextrins and alginates have been elaborately reviewed, including the effects of halide addi-tives on their anticorrosion performances. Aspects of computational/theoretical approach to corrosionmonitoring have been recommended for future studies. This non-experimental approach to corrosioncould foster a better understanding of the corrosion inhibition processes by correlating actual inhibitionmechanisms with molecular structures of these carbohydrate polymers.
© 2015 Elsevier Ltd. All rights reserved.

ontents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3151.1. Greenness: A prerequisite requirement for selection of inhibitor compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315

2. Green carbohydrate polymers application for metal protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3152.1. Exudate gums . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3162.2. Carboxymethyl and hydroxyethyl cellulose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3182.3. Starch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3222.4. Pectin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3232.5. Pectate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3252.6. Chitosan and substituted/modified chitosans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3252.7. Carrageenan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3312.8. Dextrin and cyclodextrins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332
2.9. Alginates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3. Effect of halide ion additives on corrosion inhibition with carbohydrate p4. Future perspective: Computational approach to corrosion inhibition eva

∗ Corresponding author. Tel.: +966 3 8609702; fax: +966 3 8603996.E-mail address: [email protected] (S.A. Umoren).

ttp://dx.doi.org/10.1016/j.carbpol.2015.12.038144-8617/© 2015 Elsevier Ltd. All rights reserved.

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luation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337

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S.A. Umoren, U.M. Eduok / Carbohydrate Polymers 140 (2016) 314–341 315

5. Concluding remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338

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Generalrequirem ents

Ability to oxidize the metal thereby forming a passive/protective layer on the metal sur face .

Presence of fun cti ona l groups conta ining het ero-a toms (N,O,S etc ) which can don ate thei r lon e pa irs of elec trons.

Organic moleclues should posses a la rge st ructu re, π-bond, several active chemical groups.

Poss ess ion of π-bo nd charact er wil l provide the ne eded ele ctrons to interact with the metal su rface (e.g . empt y 3d orbital of Fe) .

Ability to cover a la rge ar ea of a metal sur face with a firmly attached/ compact fil m.

Cost e ffecti veness, especiall y wh en quant ity is a fac tor of choic e.

Solubility of the inhibitor.

Non-toxic to man and nature: environmental friendline ss. GREENESS

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Introduction

Metals corrode, and this electrochemical process has hugemplication on their end-use and consequently, the economics of

aintenance and repairs for industrial applications. Several formsf corrosion products and all possible reactions, including stablehases, are revealed in the Pourbaix diagram of metals showingheir susceptibility to corrosion depending on the pH. The ratef metal corrosion is greatly influenced by substrate and surfacehemistries as well as some environmental influences (e.g. tem-erature, solution concentration (pH) etc.), and by understandinghese factors, adequate control method can be employed to revertts degradation kinetics. By studying corrosion, researchers world-

ide aim at discovering more reliable methods and strategies ofreventing, or at least minimizing its spontaneous dynamics. These of corrosion inhibitor compounds (single/multiple component,omposites and blends etc.) is by far one of the most applied corro-ion control strategy in oil-fields. This operation is effective if thedsorption mechanism(s) of the adsorbed inhibitor compound athe metal surface is rightly defined. Generally, a common mecha-ism of action of most inhibitor compounds involves the formationf passivation layer that prevents the passage of corrosive ions tohe metal surface. However, the effectiveness of this layer dependsn the environment to which the compound has been applied, theetal type as well as the fluid composition, quantity of water, and

ow regime (Gräfen, Horn, Schlecker, & Schindler, 2002). Normallyn the field, these compounds are added in small concentrationso coolants, hydraulic fluids, or any other fluid (liquid or gas) sur-ounding the metal substrate, like alkylaminophosphates and zincithiophosphates in fuel oil. Phosphates, and other inorganic sub-tances (e.g. chromates, dichromate and arsenates) are known toave detrimental environmental effect and man health impact,s such their usage is against modern safety regulation for thendustrial chemicals with severe criticism. Currently, there is anncreasing quest for limiting field applications involving toxic com-ounds, hence the search for greener alternatives by reformulatinghe existing products or by identifying new chemistries for devel-ping safer products (Killaars & Finley, 2001).

.1. Greenness: A prerequisite requirement for selection ofnhibitor compounds

The general requirements of the selection of compounds areot limited to the chemical structural pre-requite in Scheme 1,ut must also include eco-friendliness and benignity (Umoren,gbobe, Igwe, & Ebenso, 2008a; Umoren, Obot, & Obi-Egbedi,009a; Umoren, Eduok, Solomon, & Udoh, 2011; Okafor et al.,008; Obot, Obi-Egbedi, & Umoren, 2009). In recent times, owingo global interest on environment safety as well as the effect ofmpacting industrial activities of man’s health and ecological bal-nce, the use of toxic chemicals and operations that emit themave been minimized. On this note, the inorganic inhibitors andome of their hazardous organic counterparts, though effectiveor the reduction of metal corrosion at lower concentration, areradually replaced by greener substances. Generally, eco-friendly,r simply green, corrosion formulations (inhibitors and coatings)
re those chemical products that meet the required reduced levelf hazardous substance generation, and the processes involv-ng their usage are governed by sustainable chemistry withoutirect or indirect negative environmental or health impacts. Since
Scheme 1. General pre-requite requirements for the selection of inhibitor com-pounds.

recommended anticorrosive coating systems are expected to begreen and purely cured granules/powders with very low volatileorganic compound (VOC) content and without heavy metals,their inhibitor counterparts should also meet these green labelcompliant standards. With the banning of chromates, corrosioncontrol programs with greener inhibitor compounds (chromate-free inhibitor formulations) in most oil field applications aredesigned to effectively meet safety standards and also efficientlyprotect the targeted metal substrates in their service environments.Health defects of chromates ranges from mild skin allergic reactionsand rashes to nasal bleeding; with arsenates, alteration of geneticmaterial may occur at higher dosages as well as nervous break-down and cancer. The US National Institute for Occupational safetyand Health (NIOSH) have reduced the permissible exposure limit(PEL) for arsenates and chromates to 0.002 and 0.05 milligrams percubic meter of air, respectively. (https://www.osha.gov/OshDoc/data General Facts/hexavalent chromium.pdf; https://www.cdph.ca.gov/programs/hesis/Documents/arsen2.pdf).

2. Green carbohydrate polymers application for metalprotection

Organic corrosion inhibitors are generally used as replacementsfor inorganic compounds in the control of dissolution of the metalsin aqueous media. Huge interest in this class of compounds has con-tinued to grow in the last decade as naturally occurring and somesynthetic biopolymers as well as their products meet the envi-ronmental requirements for safe product application with goodcorrosion inhibiting potential with infinitesimally small/reducedor zero pollution risk. Carbohydrate polymers are widely used asmetal linings, and protective coatings. In corrosion inhibition, theyrepresent a set of chemically stable, biodegradable and ecofriendlymacromolecules with unique inhibiting strengths and mechanisticapproaches to metal surface and bulk protection (Raja et al., 2013),with those extracted from natural sources (e.g. floral) regraded as
low cost, renewable and readily available alternatives with essen-tial and active ingredients responsible for the corrosion inhibition(Rahim, Rocca, Steinmetz, & Kassim, 2008). Generally, some ofthese carbohydrate biopolymers are relatively high molecular mass
https://www.osha.gov/OshDoc/data_General_Facts/hexavalent_chromium.pdf;











https://www.cdph.ca.gov/programs/hesis/Documents/arsen2.pdf










316 S.A. Umoren, U.M. Eduok / Carbohydrat

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cheme 2. Possible mechanisms of inhibition with carbohydrate polymers.

ompounds with unique colloidal properties. Gum Arabic, fornstance, readily forms low viscous suspensions and/or gels thatan absorb water to a great extent when dissolved in appropri-te solvent (Umoren et al., 2006a; Umoren, Ogbobe, & Ebenso,006b). In solution, since the initial adsorption of inhibitor com-ounds could be affected by foreign surface active molecules, theotential of these polymers to actually reduce corrosion on theurface of a metal depends also on the adhesion of their moi-ties on the metal surface, either by physical forces or chemicalond. To really understand the surface chemistry, the potentialor inhibition of these compounds is explained in terms of their

acromolecular weights, chemical composition and the nature ofhe substrate’s surface. Some carbohydrate biopolymers normallyan restrict the rate of anodic dissolution by forming blankets onhe metal surface or deters associated cathodic reactions by activeite blocking which may largely also depend on nature (struc-ural and chemical characteristics) of the adsorption layers formedEddy, Ibok, & Ebenso, 2010; Umoren, Eduok, & Solomon, 2014;moren, Solomon, Israel, Eduok, & Jonah, 2015a). Scheme 2 showsossible mechanisms of inhibition with carbohydrate biopolymersArthur, Jonathan, Ameh, & Anya, 2013). Because of their versa-ility as non-metallic materials, some carbohydrate biopolymersre widely replacing corrosive resistance alloyed steels and non-errous metals in many industrial applications with anticorrosionoles especially in protection of metal parts (e.g. screws) subjectedo corrosion, erosion and cavitation (Klinov, 1962).

This unique class of polymers has been widely reported as cor-osion inhibitors due to their enormous functional groups and theirbility to complex with ions of metals at surfaces. By covering largeurface areas of metals in aqueous media, these complexes virtu-lly “blankets” the surface from attack by corrosive molecules andons thereby offering the needed protection. The efficacy of carbo-ydrate biopolymers as inhibitors varies with their class dependingn their molecular weights, cyclic rings as well as the availability ofond-forming groups (e.g. sulphonic acid groups) and abundancef centers of adsorption (e.g. heteroatoms) (Rajendran, Sridevi,nthony, John, & Sundearavadivelu, 2005). The presence of non-onded/lone pairs of electrons (as well as pi electrons) on theolecules of these polymeric compounds allows for inhibitor-etal electron transfer with formation of bond whose strength is a

unction of the polarizability of the electron-donating group.

.1. Exudate gums

Exudate gums are generally viscous tree (not excluding largerhrub) polysaccharides secretions that feel relatively moistennd/or sticky when wet and harden when they are dried. Thisnique physical property makes them useful oil and gas indus-rial adhesives and binders (Chaires-Martínez, Salazar-Montoya,

Ramos-Ramírez, 2008); and are used in the food industries asydrocolloids due to their thickening and stabilizing properties
Douiare & Norton, 2013). Gums are also widely used as microen-apsulating agents in pharmaceuticals. Their solubility aids theirsage as gelling and emulsifying agents as well. Depending onheir compositions and floral sources, some gums possess faint to
e Polymers 140 (2016) 314–341

very pungent scents, and are generally soluble in water with gentlestirring in small concentrations. It is not strange that some galac-tomannan gums are also found in few leguminous seed endospermlike locust bean and guar gums extracted from Ceratonia sili-qua and Cyamopsis tetragonoloba, respectively (Busch, Kolender,Santagapita, & Buera, 2015). Researches involving various gumtypes, both natural and synthetic, abound in the literature. Kim,Choi, Kim, and Lim (2015) have investigated the solubility of threegum types from tapioca starch pastes, Gum arabic, k-carrageenan,gellan in water, alongside solvent effect on their humidity stabil-ity and mechanical properties. The degradation of locust bean gumby ultrasonication at room temperature has been studied by Li andFeke (2015) with the rate of aqueous dissociation observed to bedependent on changes on molecular conformation of the gum aswell as ionic conditions in the saline media used. Depending onthe gum type, their intrinsic viscosities are widely studied by sim-ple rheological measurements. Gums are either natural or syntheticwith varying viscosities and compositions. Natural gums are classi-fied based on their sources; they are either charged (ionic; e.g. Agarextracted from seaweeds) or virtually uncharged (e.g. Guar gumfrom Guar bean seeds) polymers. Because of their unique chemi-cal composition, gums from natural sources are effective corrosioninhibitors, and their evolution has greatly attracted attention con-siderably in the corrosion field. Gums of this class are greener, andrenewable, without threat to the environment to which they areused (Umoren et al., 2006a, 2006b). Gum Arabic (GA) has beenemployed as corrosion inhibitor for some metal substrates, andavailable reports in the literature show that it protects metals toa great extent in aqueous acid and alkaline media. GA is watersoluble, a dirty sticky and wet exudate extracted from Acacia tree(Leguminosae) sap material; and it is a mixture of some polysaccha-rides, sucrose, oligosaccharides, arbinogalactan and glucoproteinsconceived to have the needed corrosion inhibition potential formetal substrate protection (Verbeken, Diercka, & Dewttinck, 2003).The use of GA for aluminium and mild steel corrosion inhibitorin 1 M sulphuric acid has been reported using the classical corro-sion monitoring techniques (Umoren, 2008). Results from weightloss and thermometric techniques revealed that GA protected bothmetals remarkably in the solution of the aerated acid with theinhibition efficiency (%�) and the degree of surface coverage (�)increasing with the concentration of GA. Physical and chemicaladsorption mechanisms where proposed for MS and Al corrosion,respectively, in the presence of GA, and its spontaneous adsorp-tion was approximated with Temkin and El-Awady et al. adsorptionisotherm models. From the results obtained, GA was concluded asa more effective inhibitor for Al in the acid solution than mild steel.In alkaline (0.1 M NaOH) medium, the effectiveness of GA towardsthe corrosion inhibition of Al with and without iodide ion (as KI)additives has also been studied by Umoren (2009) and Umorenet al. (2006a, 2006b) at 30 and 40 ◦C, using hydrogen evolutionand thermometric techniques. The corrosion inhibition of GA ofAl in 0.1 M NaOH was enhanced in the presence of the iodide ionsdue to synergistic effect. In the absence of KI, the inhibition of Alcorrosion by GA was GA-concentration and temperature depend-ent, chemisorption mechanism was proposed for GA inhibition andits adsorption on Al substrates followed Langmuir and Freundlichadsorption isotherms.

Guaran, or simply, Guar gum (GG), extracted from guar beanseed endosperm is another class of anticorrosion gum reportedin the literature. Abdallah (2004) was the first to report its anti-corrosion behaviour for carbon steel (L-52 grade) in 1 M H2SO4containing NaCl as the corrodent using Tafel polarization and
weight loss techniques. His research results revealed GG as a mixedtype inhibitor and values of inhibition efficiency (%� increasedwith its concentration for both corrosion monitoring techniques.GG adsorption on L-52 substrate followed Langmuir adsorption


Table 1Typical examples of inhibition systems involving exudate gums deployed for metal corrosion reduction in various aggressive media.

S/N Inhibitor system Inhibitor type Type of metal substrate Corrosive media Method(s) of corrosionmonitoring

References

Exudate gum1. Gum Arabic – Aluminium/mild steel 0.1 M H2SO4 Weight loss and thermometric

techniquesUmoren (2008)

2. Gum Arabic incombination withpotassium iodide

– Aluminium 0.1 M NaOH Weight loss and hydrogenevolution techniques

Umoren (2009)

3. Gum Arabic – Aluminium 0.1 M NaOH Hydrogen evolution andthermometric techniques

Umoren et al.(2006a, 2006b)

4. Guar gum Mixed type Carbon steel (L-52grade)

1 M H2SO4 containingNaCl

Weight loss andpotentiodynamic polarizationtechniques

Abdallah (2004)

5. Exudate gum extractedfrom Ficus glumosa

– Mild steel 0.1 M H2SO4 Weight loss, hydrogen evolution,thermometric techniques andscanning electron microscopy

Ameh et al. (2012)

6. Exudate gum extractedfrom Ficus benjamina

– Aluminum alloy sheet 1 M HCl GCMS and FTIR (determination ofthe chemical composition of thegum exudate); weight losstechnique

Eddy et al. (2014)

7. Exudate gum extractedfrom Acacia sieberiana

– Zinc (A72357 grade) 0.1 M H2SO4 GCMS (determination of thechemical composition of the gumexudate); weight loss, hydrogenevolution and thermometrictechniques; scanning electronmicroscopy

Ameh and Eddy(2014)

8. Exudate gum extractedfrom Daniella olliverri

– Mild steel 0.1 M HCl GCMS and FTIR (determination ofthe chemical composition of thegum exudate); weight losstechnique

Eddy et al. (2012)

9. Exudate gum extractedfrom Acacia tree

Mixed type Mild steel 0.5–2 M HCl and H2SO4 Weight loss, hydrogen evolution,and Potentiodynamicpolarization techniques; X-rayphotoelectron spectroscopy,Fourier transform infra-redspectroscopy and scanningelectron microscopy

Abu-Dalo et al.(2012)

10. Exudate gum extractedfrom Ferula assa-foetidaand Dorema ammoniacum

Mixed type Mild steel 2 M HCl Electrochemical impedancespectroscopy, Potentiodynamicpolarization, scanning electronmicroscopy; quantum chemicalcalculations (by semi-empiricalmethod/Austin Model (AM1)method)

Behpour et al.(2011)

11. Exudate gum extractedfrom Raphia hookeri

– Aluminium (AA 1060grade)

0.1 M HCl Weight loss and thermometrictechniques

Umoren, Obot,Ebenso, andObi-Egbedi (2009b)

12. Exudate gum extractedfrom Dacroydes edulis

– Aluminium (AA 1060grade)

2 M HCl Weight loss and thermometricmethods

Umoren et al.(2008b)

13. Polyacrylamide graftedguar gum

Mixed type Mild steel 1 M HCl Weight loss technique, Fouriertransform infra-red;Electrochemical impedancespectroscopy, Potentiodynamicpolarization; scanning electronmicroscopy

Roy, Karfa,Adhikari, and Sukul(2014)

14. Gum Arabic Mixed type API 5L X42 pipelinesteel

1 M HCl Potentiodynamic polarizationand Electrochemical impedancespectroscopy; Fourier transforminfra-red spectroscopy

Bentrah, Rahali,and Chala (2014)

15. Xanthan gum andXanthangum-polyacrylamideconjugate

Mixed type Mild steel 15% HCl Weight loss technique,Electrochemical impedancespectroscopy, Potentiodynamicpolarization; scanning electronmicroscopy

Biswas et al. (2015)

16. Polyacrylamide grafted Mixed but Mild steel 0.5 M H2SO4 Weight loss, potentiodynamic Banerjee,

iwTtea

with Okra mucilage predominantlycathodic

sotherm and the pitting corrosion potential (Epit) was found to varyith chloride ion concentration in the solution of the electrolyte.

he applications of exudate gums from plants sources are inexhaus-ive. Ameh’s group has reported the corrosion inhibition of gumxudates extracted from Ficus glumosa (GFG), Ficus Benjamina (GFB)nd Acacia Sieberiana (GAS) for mild steel (MS), Al and Zn corrosion

polarization and electrochemicalimpedance spectroscopy;scanning electron microscopy

Srivastava, andSingh (2012)

in 0.1 M H2SO4 and 1 M HCl (Ameh, Magaji, & Salihu, 2012; Ameh& Eddy, 2014; Eddy, Ameh, & Odiongenyi, 2014). Corrosion inhibi-
tion of GF for mild steel followed chemical adsorption mechanismand its adsorption was approximated with Langmuir adsorptionmodel (Ameh et al., 2012). Using classical (weight loss, gasomet-ric and thermometric) and surface analytical (scanning electron

3 hydrate Polymers 140 (2016) 314–341

mptgt(AaIutwfibemsatAafcmb(eHcesuctatoFi(FcceLtgwmtMssitgloTwMosri

18 S.A. Umoren, U.M. Eduok / Carbo

icroscopy, SEM) techniques, authors claimed that the inhibitingroperties of GFB could be largely attributed to a multiple adsorp-ion of its chemical constituents (tannins, polysaccharides andlucoproteins characterized by gas chromatography–mass spec-rometry (GC–MS) and Fourier transform infra-red spectroscopicFTIR) techniques) on MS. Results followed the same trend forl corrosion except that GFG adsorption on Al followed Frumkinnd Dubinin–Radushkevich adsorption models (Eddy et al., 2014).n sulphuric acid, zinc corrosion inhibition has also been studiedsing GAS with weight loss, thermometric and scanning elec-ron microscopic techniques. GAS adsorption was approximatedith Frumkin adsorption model, and its corrosion inhibition was

ound to be concentration and temperature dependent. Protectivenhibitor layer on the surface of the metal substrate was revealedy SEM (Ameh & Eddy, 2014). The chemical composition of gumxudate extracted from Daniella olliverri (GDO) has been deter-ined using GCMS and FTIR to contain stearic and phthalate acids,

ucrose, 2,6-dimethyl-4-nitrophenol and (E)-hexadec-9-enoic acid,nd mild steel corrosion inhibition with GDO has been attributed tohe adsorption of these compounds in 0.1 HCl (Eddy, Odiongenyi,meh, & Ebenso, 2012). In this study, authors investigated thedsorption and thermodynamic behaviour of GDO. While resultsrom weight loss technique reveals a dependence of %� on theoncentration of the exudate gum, its adsorption followed Lang-uir adsorption isotherm and the inhibition of GDO was entirely

y physical adsorption. Abu-Dalo, Othman, and Al-Rawashdeh2012) have also studied the inhibition effect of exudate gumxtracted from Acacia trees (GAT) on MS corrosion in 0.5–2 MCl and H2SO4. A concentration range of 0.1–0.6 mg/l GAT washosen for this study investigated using weight loss, hydrogenvolution, and electrochemical polarization, X-ray photoelectronpectroscopy (XPS), FTIR and SEM. For both acid corrodents, val-es of %� increased with inhibitor concentration but GAT inhibitedorrosion in HCl more than H2SO4. The magnitude of %� was foundo increase with external magnetic field in the presence of GATlso revealed to be a mixed type inhibitor. Steel corrosion inhibi-ion was attributed to the adsorption of GDO films on the surfacef the metal substarte, and this was confirmed by results fromTIR, SEM and XPS. Investigated with classical and electrochem-cal techniques, Behpour, Ghoreishi, Khayatkashani, and Soltani2011) have reported the effects of exudate gum extracts fromerula assa-foetida (GFF) and Dorema ammoniacum (GDA) on theorrosion inhibition of MS corrosion in 2 M HCl solution. From Tafelurves, the authors concluded that the gums from both sourcesxhibited mixed type behaviour, and their adsorptions followedangmuir isotherm. The magnitude of %� for steel in the solu-ion of the acid electrolyte decreased with temperature for bothum resins. Inhibition of MS in the presence of GFF and GDAas attributed to adsorption of components of the gums unto theetal substrate in the corrodent; authors further performed quan-

um chemical calculations (by the semi-empirical method/Austinodel (AM1) method) illustrating the adsorption processes of

ome of these chemical components. SEM results revealed moreurface pitting for MS substrate in the corrosion media contain-ng GFF compared to GDA. Umoren et al. (2009a) have reportedhe corrosion inhibition of Al in HCl in the presence of exudateum from Raphia hookeri (GRH) at 30–60 ◦C. Results from weightoss and thermometric techniques show that the performancef GRH improved with concentration and not with temperature.he physical adsorption mechanism of GRH was approximatedith Temkin adsorption isotherm and Kinetic–Thermodynamicodel of ElAwady et al. Al corrosion inhibition in the presence

f GRH was also attributed to the adsorption of its phytocon-tituents. Biswas, Pal, and Udayabhanu (2015) have recentlyeported the inhibition effect of Xanthan exudate gum (Fig. 1) andts graft polyacrylamide co-polymer on MS corrosion in a very high

Fig. 1. Molecular structure (repeat unit) of Xanthan gum.

concentration of acid (15% HCl) using chemical, electrochemicaland surface analytical techniques. For all the techniques used inthis study, values of %� increased with inhibitor concentrationand the gum inhibited HCl induced corrosion up to 92% inhibi-tion efficiency—remarkably higher for this corrodent concertation(15% HCl). The gum inhibition system acted as a mixed typeinhibitor with molecular adsorption at the metal surface initiat-ing corrosion inhibition as confirmed by SEM analysis. Improvedinhibition was revealed in the presence of polyacrylamide. Inhibi-tion mechanism was elucidated by means of thermodynamic andkinetic parameters and Xanthan gum adsorption and in combina-tion with the copolymer on the metal surface followed Langmuirisotherm model. Authors also correlated the experimental resultswith theoretical evaluation of associated monomeric units usingDFT in other to correlate inhibitor molecular structure with cor-rosion inhibition. The inhibition performance of exudate gumextracted from Dacroydes edulis (Umoren, Obot, Ebenso, & Obi-Egbedi, 2008b) including exudate gum extracts from other floralsources investigated in acidic and alkaline media are presented inTable 1, well as their corrosion behaviours for respective metalsubstrates as reported in the literature. Apart from the uniquechemical constituents of individual gums from different sources,their solubility in aqueous media allows for their wide applica-tion in corrosion inhibition. In aqueous media, dried gum mattersadsorb water and gradually swell, then gel, dissolving without agi-tation since the consist of complex mixtures of polysaccharides.Peter, Obot, and Sharma (2015) have recently given a comprehen-sive review of some green gums for corrosion inhibition in orderof class/source as well as their solubility in the media. Table 1 fea-tures reviewed examples of other exudate gums reported in theliterature

2.2. Carboxymethyl and hydroxyethyl cellulose

Cellulose gum or simply, carboxymethyl cellulose (CMC), isavailable as a sodium salt. It has structural features of normalcellulose but with reactive carboxymethyl groups attached to thehydroxyl groups of its cellulosic glucopyranyl moiety (Fig. 2) (Peteret al., 2015).

Derived from molecular cellulose, CMC could be one of the most
abundant water-insoluble polysaccharide used in similar industrialapplications as exudate gums as they are better binders, thickener,stabilizers for food and pharmaceutics (Solomon, Umoren, Udosoro,& Udoh, 2010). CMC is widely synthesized via alkali-assisted


Table 2Typical examples of inhibition systems involving substituted cellulose and starch deployed for metal corrosion reduction in various aggressive media.

S/N Inhibitor system Inhibitor type Type of metalsubstrate/corrosivemedia

Method(s) of corrosionmonitoring

Reason for corrosioninhibition/corrosion reductionis attributed to the followingreason(s)

References

Carboxymethyl celluloseand Hydroxyethyl cellulose

1. Carboxymethyl cellulose – Mild steel/2 MH2SO4

Weight loss, hydrogenevolution andthermometric techniques

Authors attributed chemicaladsorption via inherentfunctional groups (e.g.

COOH) on the metal surfaceas the reason for corrosioninhibition; they pointed outthat the protonated of COOHat the carbonyl group aidedmolecular adsorption onto thecharged metal surface byelectrostatic interaction

Solomon et al.(2010)

2. Sodium carboxymethylcellulose

Mixed type Mild steel/1 M HCl Weight loss techniques;potentiodynamicpolarization, linearpolarization resistance andelectrochemicalimpedance spectroscopy

Molecular adsorption on themetal surface via inherentfunctional groups

Bayol, Gürten,Dursun, andKayakirilmaz(2008)

3. Carboxymethyl cellulosein combination withpotassium halides (KCl,KBr, KI)

– Mild steel (AISI1005 grade)/2 MH2SO4

Weight loss and hydrogenevolution techniques

Inhibitor molecular adsorptionon the metal surface; Halideions demonstrated bothantagonism (Cl− and Br− ions)and synergism towards theinhibition potency ofCarboxymethyl cellulose

Umoren et al.(2010)

4. Carboxymethyl cellulose[Authors also studiedpoly(vinyl alcohol),poly(acrylic acid), sodiumpolyacrylate,poly-(ethylene glycol),pectin]

Slightlycathodic athighercarboxymethylcelluloseconcentrations

Planar cadmiumdiscelectrode/0.5 M HCl

Potentiodynamicpolarization andelectrochemicalimpedance spectroscopy

Molecular adsorption on themetal surface

Khairou andEl-Sayed(2003)

5. Carboxymethyl cellulosein combination with1-hydroxyethanole-1,1-diphosphonic acid–Zn2+

system

Mixed type Mild steel/Neutralaqueousenvironmentcontaining 60 ppmCl−

Weight loss technique;[protective film has beenanalyzed by X raydiffraction (XRD) andFTIR]; Potentiodynamicpolarization technique

Formation of protectivecomplex (Zn(OH)2, Fe2+–HEDPtype and Fe2+–CMC complex)films on the surface of themetal substrate; confirmed byX-ray Diffraction and Fouriertransform Infra-redspectroscopy

Rajendran et al.(2002)

6. Carboxymethylcellulose–Zn2+ binarysystem

Mixed type;but dominantlyanodic

Carbonsteel/Neutralchlorine ion(120 ppm Cl−)saturated media

Weight loss andpotentiodynamicpolarization techniques,electrochemicalimpedance spectroscopy

Inhibition was attributed toZn2+–CMC type protective filmon metal surface, confirmed byAFM; This film was confirmedto be made of Fe2+–CMCcomplex and Zn(OH)2 usingFTIR

Antony et al.(2010)

7. Carboxymethylcellulose–Zn2+ binarysystem

Mixed type;butpredominantlycathodic

Aluminium/Groundwater at pH 11

Weight loss andpotentiodynamicpolarization techniques,electrochemicalimpedance spectroscopy

Formation of protective film onthe metal surface (confirmedwith scanning electronmicroscope and atomic forcemicroscopy)

Kalaivania et al.(2013)

8. Carboxymethylcellulose–Zn2+ system

– Carbonsteel/Ground waterat pH 11

Weight loss technique andelectrochemicalimpedance spectroscopy

Rate of metal degradation wasattributed an inhibitionsynergism between Zn2+ andCMC; and also the formation ofprotective film on the metalsurface (confirmed withscanning electron microscopy)

Manimaranet al. (2013)

9. Hydroxypropyl cellulose[Authors also studiedglucose and gellan gum] incombination withpotassium iodide

Mixed type Cast iron/1 M HCl Weight loss andpotentiodynamicpolarization techniques,electrochemicalimpedance spectroscopy

Molecular adsorption on themetal surface confirmed byWide angle X-ray diffraction,Fourier transform Infra-redspectroscopy and scanningelectron microscope;potassium iodidedemonstrated bothantagonism and synergismtowards the inhibition potencyof Hydroxypropyl cellulose

Rajeswari et al.(2013)

320 S.A. Umoren, U.M. Eduok / Carbohydrate Polymers 140 (2016) 314–341

Table 2 (Continued)




References

10. Hydroxyethyl cellulose Mixed type Carbon steel (1018grade)/3.5% NaCl

Electrochemicalimpedance spectroscopy,potentiodynamicpolarization andelectrochemical frequencymodulation. Authorsfurther explained inhibitormolecular adsorption andcorrosion mechanism withDMol3 quantum chemicalcalculations

Molecular adsorption on themetal surface (confirmed withscanning electronmicroscopy/Energy dispersiveX-ray spectroscopy)

El-Haddad(2014)

11. Hydroxyethyl cellulosein combination withpotassium iodide

Mixed type Mild steel/0.5 MH2SO4

Weight loss andpotentiodynamicpolarization techniques;electrochemical impedancespectroscopy. Quantumchemical calculations usingthe density functionaltheory (DFT) wasemployed to determine therelationship betweenmolecular structure andinhibition efficiency

Metal corrosion inhibition wasattributed to Hydroxyethylcellulose molecular adsorptionand elastic film formation onthe steel substrate due to thepresence of this compound inthe test solution. Potassiumiodide enhanced the inhibitionperformance of the system bybridging the charged steelsubstrate and the organicinhibitor

Arukalam et al.(2015)

12. Hydroxyethyl cellulose Mixed type Mild steel/1 and1.5 M HCl; 0.5 MH2SO4

Weight loss technique;Potentiodynamicpolarization andelectrochemicalimpedance spectroscopy

Inhibitor molecular adsorptionon the metal surface

Arukalam(2012),Arukalam,Madufor,Ogbobe, andOguzie (2014d)

13. Hydroxyethyl cellulose Mixed type Cylindrical zincsubstrate(Zinc-carbonbattery)/26% NH4Cl

Potentiodynamicpolarization andelectrochemicalimpedance spectroscopy

Inhibitor molecular adsorptionon the metal surface(confirmed with Fouriertransform Infra-redspectroscopy and scanningelectron microscopy)

Deyab (2015)

14. Methyl cellulose Anodic aluminum andaluminum siliconalloys/0.1 M NaOH

Potentiostatic polarization,electrochemicalimpedance spectroscopy,cyclic voltammetry andpotentiodynamic anodicpolarization techniques

Inhibitor molecular adsorptiondue to the presence of methylcellulose at the surface of alloys

Eid et al. (2015)

Starch15. Starch in combination

with 2,6-diphenyl-3-methylpiperidin-4-one

Mixed type Mild steel/1 N HCl Weight lossmeasurements;ElectrochemicalImpedance Spectroscopy;Potentiodynamicpolarization

Both compoundssynergistically inhibited steelcorrosion by combinemolecular adsorption at themetal surface (including claimsof the formation of protectivelayer confirmed with Fouriertransform Infra-redspectroscopy)

Brindha et al.(2015)

16. Starch in combinationwith sodium dodecylsulfate and cetyl trimethylammonium bromide

Mixed type butpredominantlyanodic

Mild steel/0.1 MH2SO4

Weight loss andpotentiodynamicpolarization

Both natural and syntheticcompounds synergisticallyinhibited steel corrosion bycombine molecular adsorptionat the metal surface

Mobin et al.(2011)

17. Activated andcarboxymethylated starchcassava starch

– XC 35 carbonsteel/Alkaline200 mg/l NaCl

ElectrochemicalImpedance Spectroscopy

Inhibitor molecular adsorptiondue to the presence of starch atthe surface of steel (confirmedwith Atomic force microscopy).Corrosion inhibition increasedwith the concentration ofstarch in both cases withcarboxymethylated starchbeing the less performedinhibitor due to molecularsubstitution of its activehydroxyl groups

Bello et al.(2010)


Table 2 (Continued)




References

18. Tapioca starch Mixed type AA6061alloy/seawater

Gravimetric,potentiodynamicpolarization, linearpolarization resistance andelectrochemicalimpedance spectroscopy

Physical coverage as well asmolecular adsorption at themetal surface (confirmed withscanning electron microscopy).Theoretical approach tocorrosion inhibition was alsoemployed in correlatinginhibiting mechanism withmolecular structure

Rosliza and Nik(2010)

19. Acryl amide graftedcassava starch

Mixed typethoughpredominantlyanodic andcathodic atlower andhighertemperatures,respectively

Cold rolledsteel/1 M H2SO4

Weight loss,potentiodynamicpolarization,electrochemicalimpedance spectroscopy

Improved protection from thisconjugate is due to synergybetween both compounds bycombine molecular adsorptionat the metal surface (confirmedwith scanning electronmicroscopy)

Li and Deng(2015)

20. Polyorganosiloxane-grafted potato starchcoatings

– Aluminium/neutralelectrolyte

EIS and salt-sprayresistance for 288 h

Improved protection wasattributed topolyorganosiloxane polymersgrafted onto polysaccharidecoated on the Al substrate

Sugama andDuVall (1996)

21. Cerium (IV) ammoniumnitrate modifiedpotato-starch

– 6061–T6aluminium/neutralelectrolyte

Salt-spray tests, EIS andsurface analyticaltechniques (FTIR and XPS)

Improved protective propertiesof this composite wasattributed to the formation ofcerium-bridged carboxylatecomplexes by carboxylatefunctional group with Ce4 ions

Sugama (1997)

FH

cbatbpTfsS(aopmbs(3cates

have also reported the effect of CMC on the inhibition properties

ig. 2. Molecular structure of carboxymethyl cellulose [R = H or CH2COOH] andydroxyethylcellulose [R = H or CH2CH2OH].

ellulose/chloroacetic acid reaction. In acid-induced corrosion inhi-ition, the protective ability of CMC on steel is alleged to be due to

possible physisorption of protonated CMC via molecular attrac-ion with the negative charged mild electrode weakly adsorbedy hydrated ions of electrolyte anions. CMC protonation occursrimarily at the carbonyl group, normally forming polycations.he anti-corrosive properties of CMC have been widely studiedor mild steel in different acid solutions. Bayol et al. (2008) havetudied the adsorptive behaviour of CMC on MS in HCl solutions.olomon et al. (2010) and Umoren, Solomon, Udosoro, and Udoh2010) have reported the inhibition potential of CMC for sulphuriccid corrosion of MS and also the effects of synergism and antag-nism of halide ions with CMC on corrosion inhibition. Table 2resents a list of substituted cellulosic compounds deployed foretal corrosion reduction in various aggressive media. In the work

y Solomon et al. (2010), CMC have been assessed as a green corro-ion inhibitor for MS in 2 M H2SO4 by means of chemical techniquesweight loss, hydrogen evolution and thermometric methods) at0–60 ◦C. It was found that values of %� greatly increased with CMConcentration and not with temperature. This physical mode of
dsorption followed Dubinin–Radushkevich and Langmuir adsorp-ion isotherms; and the inhibition mechanism was corroborated byxperimentally derived activation/kinetic parameters. Under theame experimental condition, authors further studied the effect of
at the metal/coating interface

halide ions (Cl−, Br−, and I−) additives on the performance of CMCin the acid medium (Umoren et al., 2010). The corrosion inhibi-tion by CMC was enhanced in the presence of iodide ions, showingsynergistic effect, while the opposite was the case in the pres-ence of chloride ions (antagonistic effect). The magnitude of %�increased with immersion time of MS in the solution of the elec-trolyte containing CMC and the iodide ions, and for all the otherhalide ions. Adsorption of the halide ions followed similar isothermmodel reported by Solomon et al. (2010), and the trend in thermo-dynamic and kinetic parameters was explained accordingly withrespect to each halide ions. Bayol et al. (2008) have reported sim-ilar findings in 1 M HCl using chemical (weight loss method) andelectrochemical (potentiodynamic polarization, linear polarizationresistance (LPR), and EIS) techniques. Inhibition of MS corrosionwas found to be concentration dependent and CMC was revealedas a mixed type inhibitor. The adsorption behaviour reported inthis study follows the same trend as those previously reportedfor CMC (Solomon et al., 2010; Umoren et al., 2010). SEM analy-sis was employed in studying the adsorption of CMC on the MSsurface at room temperature. The corrosion inhibition of a planarcadmium disc electrode in 0.5 M HCl in the presence of CMC along-side five other polymers has been reported by Khairou and El-Sayed(2003) using EIS and Tafel techniques. The inhibitive action of CMCaffected only the associated cathodic processes, indicating that itwas a cathodic type inhibitor at higher concentrations. CMC’s physi-cal adsorption mode followed Temkin adsorption isotherm, and theincrease in values of %� with CMC concentration was attributed tomolecular adsorption on the cadmium disc surface. Using weightloss technique, Rajendran, Joany, Apparao, and Palaniswamy (2002)

of 1-hydroxyethanole-1/1-diphosphonic acid(HEDP)–Zn2+ binarysystem for MS in neutral chloride ion (60 ppm Cl−) saturated media.Values of %� for this system stood at 40% in the presence of 300 ppm

3 hydrat

H5rotrist2eepLMFc%tZg1MowsatRhhidwwpaLwtbtEnpmcpcsmtae

fatHptseau

enzymatic catalyzed oxidation using adenylyltransferase (Smith,


EDP and 10 ppm Zn2+ but increased to 80% with the addition of0 ppm CMC being the peak concentration. Inhibition of MS cor-osion in this neutral medium was attributed to the adsorptionf Zn(OH)2, Fe2+–HEDP type and Fe2+–CMC complexes/films onhe surface of the metal substrate. This was confirmed with X-ay diffraction (XRD) and FTIR. Another CMC–Zn2+ binary systemn neutral chloride ion (120 ppm Cl−) saturated media has beentudied for carbon steel corrosion using weight loss, EIS and poten-iodynamic polarization techniques (Antony, Sherine, & Rajendran,010). A %� magnitude of 97% was achieved at pH 7 in the pres-nce of 250 ppm CMC and 100 ppm Zn2+, though decreased atxtremely low and high pH values. CMC–Zn2+ binary system dis-layed a mixed type protection but dominantly anodic controlled.ike the work reported by Rajendran et al. (2002), inhibition ofS corrosion in corrodent was attributed to the adsorption of a

e2+–CMC type complexes/protective films. This mechanism wasonfirmed by AC impedance spectra and AFM studies. Values of� magnitude as high as 95 and 98% have also been recorded inhe presence of 250 ppm CMC (in combination with 25 and 50 ppmn2+, respectively) for aluminuim and carbon steel substrates inround water using chemical and electrochemical techniques at pH1 (Kalaivania, Arasub, & Rajendran, 2013; Manimaran, Rajendran,anivannan, Thangakani, & Prabha, 2013). CMC in the presence

f Zn2+ synergistically inhibited steel corrosion, and inhibitionas attributed to Zn2+–CMC type complexes adsorption on metal

urface characterized by SEM and AFM. Corrosion inhibition wasttributed to complex formation at the metal surface with polariza-ion result revealing that this process was predominantly cathodic.ajeswari, Kesavan, Gopiramanb, and Viswanathamurthi (2013)ave assessed the corrosion inhibition of Glucose, gellan gum, andydroxypropyl cellulose for cast iron in 1 M HCl by electrochem-

cal and chemical methods. Corrosion inhibition was found to beependent of temperature and on the concentration of CMC (asell as that of other inhibitors). Greater protection of cast ironas observed at increased inhibitor concentrations, lower tem-eratures and prolonged immersion time. CMC was revealed as

mixed type inhibiting system, while its adsorption followedangmuir adsorption isotherm. Physical adsorption mechanismas proposed form thermodynamic/kinetics parameters. Recently,

he corrosion inhibition of methyl cellulose in 0.1 M NaOH haseen reported for aluminum and aluminum silicon alloys inves-igated with electrochemical techniques (Eid, Abdallah, Kamar, &l-Etre, 2015). Results from potentiodynamic polarization tech-ique revealed that the inhibitive action of this compound systemredominantly affected the anodic process, indicating that theethyl cellulose was an anodic type inhibitor. Authors attributed

orrosion inhibition by this compound to adsorption via multi-le sites at the metal surface and the physical displacement oforrosive molecules across the metal/solution interface. Corro-ion of the alloys was found to reduce with the concentration ofethyl cellulose but not with temperature. Cellulose’s physisorp-

ion at the metal surface followed Langmuir adsorption isotherm,nd kinetic/thermodynamic parameters were calculated to furtherxplain the mechanism of molecular adsorption.

Just like CMC, hydroxyethylcellulose (HEC) is also derivedrom cellulose and used primarily as a thickening, bindingnd gelling/stabilizing agents, and employed medically for gas-rointestinal fluids drug dissolution (https://en.wikipedia.org/wiki/ydroxyethyl cellulose). The molecular structure of HEC is dis-layed in Fig. 2. It has structural features similar to CMC except forhe replacement of the carboxymethyl with hydroxyethyl groupstill attached to the hydroxyl groups of cellulosic glucopyranyl moi-
ty in the same position. The success of this carbohydrate polymers a corrosion inhibitor in different media is drawn from thesenique functional groups (OH, COOH) on its cellulose backbone
e Polymers 140 (2016) 314–341

as well as its large molecular size which ensures greater cov-erage of metal surface, deterring corrosive ions and molecules.El-Haddad (2014) have reported a corrosion inhibition efficiency(%�) in the magnitude of 97% for 5 mM HEC for 1018 grade car-bon steel in 3.5 wt% NaCl solution. The anticorrosion properties ofthis carbohydrate polymer were investigated using EIS, potentio-dynamic polarization and electrochemical frequency modulation(EFM). Electrochemical polarization result revealed that HEC was amixed-type inhibitor under this experimental condition, and cor-rosion inhibition was induced by molecular adsorption on the steelsurface confirmed by SEM/energy dispersive X-ray (EDX) analy-sis. Adsorption of HEC followed Langmuir adsorption isotherm.Adsorption mechanism was supported by DMol3 quantum chem-ical calculations as well as the computation of thermodynamicparameter and activation parameters. Arukalam, Madufor, Ogbobe,and Oguzie (2015) have also reported similar study in an aerated0.5 M H2SO4 solution using both gravimetric and electrochemi-cal techniques for mild steel corrosion. Corrosion inhibition wasfound to increase with HEC concentration and with temperature.Potentiodynamic polarization result revealed that HEC was a mixedtype inhibitor while its adsorption on the steel surface graduallydecreased double layer capacitance (Cdl). Quantum chemical calcu-lations with density functional theory (DFT) were used to correlatethe corrosion inhibition with HEC molecular structure; inhibitionwas attributed to its adsorption behaviour on the steel surface fromcomputed activation/kinetic parameters. HEC adsorption followedthe Freundlich isotherm model. Corrosion inhibition was enhancedin the presence of KI in the solution of the acid electrolyte. A corro-sion inhibition of magnitude 69.62% and 58.15% in 1 and 1.5 M HCl,respectively, has been reported by Arukalam (2012) for HEC inves-tigated by weight loss technique. He found that HEC inhibited steelcorrosion by increasing its concentration and attributed inhibitionto HEC molecular adsorption/elastic film formation on the steelsubstrate. With the ban of mercury as corrosion inhibitor for zincbatteries due to its inherent toxicity and environmental impact,researcher worldwide have focus more attention of organic com-pounds as alternative (Qu, 2006). Deyab (2015) has investigatedthe anticorrosion ability of HEC as inhibitor for zinc–carbon bat-tery using electrochemical techniques. HEC was found to inhibitcorrosion up to 92% for 300 ppm HEC at 30 ◦C. Tafel polarizationrevealed that HEC was a mixed-type inhibitor, and its ability toinhibit Zn corrosion was attributed to its adsorption on the Znsurface. Langmuir isotherm and thermodynamic parameters wereemployed in explaining HEC adsorption (both physisorption andchemisorption), as well as FTIR and SEM for characterization of theadsorbed carbohydrate biopolymeric film.

2.3. Starch

Starch is a very large carbohydrate molecule with glycosidicbonds chemically connecting its numerous glucose units. Normally,starch is consists of varying percentages by weight of amylose(linear and helical) and amylopectin (branched) molecules depend-ing on the source from which it is derived (Brown & Poon, 2005).Fig. 3 displays the molecular structures of starch. Starch biochem-ically provides the needed body energy to both higher animalsespecially as it is being indirectly consumed from green plantsources. For these plants to biosynthesize starch, series chem-istry is involved: initially, adenosine triphosphate is employed toconvert glucose-phosphate to adenosine diphosphate-glucose via

2001). Virtually every human diet taken daily contains starch inrelatively enormous abundance (in yams, cassava, cereals, pota-toes, oats, peas, nuts, etc.). Starch is basically used as common food

https://en.wikipedia.org/wiki/Hydroxyethyl_cellulose








Fs

agpu

astpclreh(2HsccTaatttmlrafufRspaesAatathic

ig. 3. Chemical structures of the amylose (a) and amylopectin (b) molecules oftarch.

dditive but also processed for use to simple sugars, thickeners andlues for use in food and other industries. This white and tastelessolysaccharide is sparingly soluble in warm water but completelyndissolved in cold water and alcoholic solvents.

The use of molecular starch as corrosion inhibitor lacks widepplication due to its reduced solubility and surface adhesiontrength. Some reports involving its application in acid and neu-ral media for metal inhibition have been reported based on eitherhysical or chemical modification in other to improve its anti-orrosion ability. The corrosion inhibiting ability of starch can beinked to its unique molecular structures (Fig. 3); bearing electron-ich hydroxyl groups capable of coordinate bonding by filling thempty or partially occupied orbitals of iron in ferrous substrates,ence corrosion inhibition. Brindha, Mallika, and Sathyanarayana2015) have recently reported the use of starch in combination with,6-diphenyl-3-methylpiperidin-4-one (DPMP) for mild steel in 1 NCl using chemical and electrochemical techniques. Steel corro-

ion rate was found to reduce with the concentrations of theseompounds, with both compounds synergistically inhibited steelorrosion by combine molecular adsorption at the metal surface.he corrosion inhibition by starch was greatly enhanced by theddition of 0.2 mM DPMP independent of the study temperaturend the immersion time. Authors also attributed corrosion inhibi-ion to the formation of protective layer confirmed with Fourierransform Infra-red spectroscopy. Experimental results were fur-her collaborated with theoretical evaluation of the relationship of

olecular structure and corrosion inhibition at the B3LYP/631G(d)evel. Results from weight loss techniques were also collabo-ated with thermodynamic and adsorption isotherm models. Innother work, starch in combination with sodium dodecyl sul-ate and cetyltrimethyl ammonium bromide have been studiedsing weight loss and potentiodynamic polarization techniquesor mild steel in 0.1 M H2SO4 (Mobin, Khan, & Parveen, 2011).esults from potentiodynamic polarization revealed that thesetarch–surfactant conjugates were a mixed type system (thoughredominantly anodic) and recorded 66.21% inhibition efficiencyt 30 ◦C with only 200 ppm starch. Just as reported by Brindhat al. (2015), author linked corrosion inhibition of both systems toynergistic or combine molecular adsorption at the metal surface.dsorption of these conjugates at steel surface followed Langmuirdsorption isotherm at the range of temperature and concentra-ion under study. Physical adsorption phenomenon was proposednd results were also collaborated with thermodynamic parame-
ers to further explain the inhibition mechanism. Bello et al. (2010)ave studied the effect of physically (activated starch) and chem-
cally (carboxymethylated) modified starch cassava starch on theorrosion of XC 35 carbon steel in alkaline 200 mg/l NaCl medium

Fig. 4. Molecular structure of pectic acid.

using electrochemical impedance spectroscopy. Inhibitor molecu-lar adsorption due to the presence of starch at the surface of steelwas concluded as the principal cause of corrosion inhibition; thiswas confirmed with atomic force microscopy in the presence andabsence of starch. Corrosion inhibition increased with the concen-tration of starch in both cases, with carboxymethylated starch beingthe less performed inhibitor due to molecular substitution of itsactive hydroxyl groups. To further explain reason for this uniquebehaviour by carboxymethylated starch, the monomeric units weretheoretically mapped (electrostatic potential mapping) to observepossible ionic interactions at the molecular level. Malaysian cas-sava (tapioca) starch has been employed in reducing the corrosionof AA6061 alloy in seawater (sourced from Terengganu port,Malaysia) using chemical and electrochemical techniques (Rosliza& Nik, 2010). The presence of starch in the neutral corrodent wasobserved to greatly reduce metal corrosion rate with huge effectson double layer capacitance and corrosion current densities. Poten-tiodynamic polarization results revealed starch inhibition processinfluenced both cathodic and anodic reactions. Corrosion reductionwas inhibitor concentration-dependent. Corrosion inhibition wasattributed to physical coverage as well as molecular adsorption ofstarch at the metal surface; further confirmed with SEM analysis.Theoretical approach to corrosion inhibition was also employed byauthors in correlating inhibiting mechanism with molecular struc-ture. Adsorption of starch followed Langmuir adsorption isothermmodel. The effect of chemical grafting of acryl amide to cassavastarch for corrosion inhibition of cold rolled steel in 1 M H2SO4 hasbeen investigated using chemical and electrochemical techniques(Li & Deng, 2015). The improved protection from this grafted con-jugate was due to a synergy between both compounds by combinemolecular adsorption at the metal surface (with the adsorption fur-ther confirmed with SEM). From the Tafel behaviour, this graftedstarch–acryl amide conjugate was observed to be a mixed typeinhibitor though predominantly anodic and cathodic at lower andhigher temperatures, respectively. Langmuir adsorption isothermwas employed in fitting the adsorption of the inhibitor adsorbedat the metal surface. The use of cerium(IV) ammonium nitratemodified potato-starch has been deployed as a primer coatings(and polyurethane top-coat) of 6061-T6 aluminium with remark-able anticorrosion properties in 0.5 N NaCl electrolyte at 25 ◦C.Corrosion tests were conducted using salt-spray tests, EIS andsurface analytical techniques (FTIR and XPS). An improved protec-tive property of this composite was attributed to the formation ofcerium-bridged carboxylate complexes by carboxylate functionalgroup with Ce4 ions at the metal/coating interface. The coating wasfound to loss adhesion on polyurethane compared to aluminiumsubstrates (Sugama, 1997).

2.4. Pectin

Pectin is a complex set of heteropolysaccharide with molecu-lar structure not restricted to Fig. 4. It is naturally abundant in cell
walls of non-woody terrestrial plants and commercially availableas white or brownish powders/granules (depending of the methodsof synthesis and purification) (Keppler, Hamilton, Bra, & Röckmann,2006). In nature, the structure and composition of floral pectin

3 hydrat

drP

P

azHtapiptcePhci(icarapbsmcawFpHfwtobaaVtfewitgcbarotpwp(tst


epend on the plant and even the plant parts; and during fruitipening, pectin is reduced to pectinesterase by pectinase (Eq. (1)).ectic polysaccharides are abundant with galacturonic acid.

ectinpectinase−→ Pectinesterase (1)

Pectin is commonly extracted from citrus and apples, and useds gelling and thickening agents in food industries and as stabili-ers in some confectionaries, as well as in drinks (Sakai, Sakamoto,allaert, & Vandamme, 1993). Since pectin normally increases

he amount and viscosity of human stool, it is medically usedgainst some chronic cases of constipation and diarrhea. Like otherolysaccharides enlisted in this review for inhibition, pectin’s abil-

ty to reduce metal corrosion is drawn from its chemistry. Pectinossess carboxylic ( COOH) and carboxymethyl ( COOCH3) func-ional groups on its carbohydrate backbone making it a possibleandidate compound for corrosion and scaling reduction in differ-nt media (Chauhan, Kumar, Kumar, Sharma, & Chauhan, 2012).ectin is a biodegradable, benign and green corrosion inhibitor. Weave recently reported the anticorrosion ability of pectin (commer-ial pectin from apple) in our laboratory against X60 pipeline steeln HCl medium using chemical and electrochemical techniquesUmoren, Obot, Madhankumar, & Gasem, 2015b). The corrosionnhibition efficiency (%�) was found to be temperature and pectinoncentration dependent; higher magnitudes of %� were obtainedt increased concentration of pectin (98.2% being the highestecorded %� for 1000 ppm pectin at 60 ◦C after 24 h immersion)nd temperature. Potentiodynamic polarization results revealedectin inhibition influenced both cathodic and anodic reactions,ut dominantly cathodic. Inhibition of X60 pipeline steel corro-ion was attributed to adsorption of protective pectin film on theetal surface, and this was further confirmed by SEM and water

ontact angle measurements. Pectin adsorption followed Langmuirdsorption isotherm, and quantum chemical calculations by DFTas employed to explain pectin’s adsorption-inhibition activity.

ares, Maayta, & Al-Mustafa, 2012a have studied the application ofectin (from citrus peel) for Al metal reduction in acidic (0.5–2 MCl) media. The magnitude of %� greater than 91% was attained

or 8.0 g/L pectin at 10 ◦C and was observed to slowly decreaseith temperature. Values of %� increased with pectin concentra-

ion, and this was consequently reflected in corresponding valuesf activation energy, enthalpy and entropy. Corrosion inhibitiony pectin was attributed to its adsorption on the metal surfacend this was confirmed by SEM analysis. Its adsorption in thiscidic media followed Langmuir isotherm. Fiori-Bimbi, Alvarez,aca, and Gervasi (2015) have reported a multi-step acid extrac-

ion of pectin from fresh lemon peel. The pectin extract was testedor anticorrosion ability for mild steel in 1 M HCl using chemical andlectrochemical methods. Mild steel corrosion was found to reduceith the addition of pectin, and this continued as the temperature

ncreased. Tafel results revealed that pectin in this study is mixed-ype inhibitor, and the reason for pectin inhibition was due toeometric blocking effect caused by chemisorbed pectin–Fe2+ typeomplexes/species at the metal/solution interface was confirmedy UV-spectroscopic analysis. Thermodynamics and kinetics ofdsorption were considered directly from the electrochemicalesults and the trend in values further added insights into the modef adsorption. The most recent pectin application for corrosion pro-ection is the work by Grassino et al. (2016). Authors extractedectin for the first time using tomato (Lycopersicum esculentum)aste. Characterization of pectin after extraction from this sourceroceeded with FTIR and nuclear magnetic resonance spectroscopy
NMRS) analyses as well as colour and rheological determina-ion. Results were compared to a commercially available pectintandard. The extracted pectin was methoxy pectin type based onhe degree of esterification result (about 82%). The pectin extract
e Polymers 140 (2016) 314–341

was employed in studying tin corrosion inhibition, and values of %�up to 73% was recorded at very low concentrations (4 g/L) using EISand potentiodynamic polarization technique in 2% NaCl, 1% aceticacid and 0.5% citric acid solution. Tafel results revealed that pectinin this study is mixed-type inhibitor. Pectin extract from Opuntiacladodes has also been employed in reducing mild steel corrosionin 1 M HCl using weight loss, potentiodynamic polarization andelectrochemical impedance spectroscopy techniques (Saidia et al.,2015). Corrosion inhibition increased with the pectin concentrationas revealed in variation in values of charge–transfer resistance andthe reduction in double-layer capacitance. Pectin from this sourceacted as a mixed inhibitor with the highest %� (96%) attained at35 ◦C in the presence of 1 g/l pectin. Pectin adsorption on the metal-lic substrate followed Langmuir adsorption isotherm. Corrosionresearches involving pectin inhibition is not limited to acid-inducedmedia, Prabakaran, Ramesh, Periasamy, and Sreedhar (2015) havereported the synergistic pectin inhibition with propyl phospho-nic acid (PA) and Zn2+ ions in neutral medium for carbon steelusing chemical and electrochemical techniques. The presence ofpectin in this study enhanced the inhibition ability of the sec-ondary components (PA and Zn2+ additives). Result from weightloss technique revealed the optimum concentration of pectin, alsoshowing that the presence of PA and Zn2+ synergistic improved cor-rosion protection by pectin. Potentiodynamic polarization resultsrevealed pectin inhibition influenced both cathodic and anodicreactions, and its adsorption was marked with decrease in val-ues of corrosion current density. Spectroscopic (FTIR) and surfaceanalytical (SEM, AFM, and XPS) techniques were employed to ascer-tain the formation of pectin-type complexes/film on carbon steel.The corrosion inhibition of pectin/ascorbic acid for tin in a neu-tral NaCl solution has been investigated (Nada, Katarina, & Sandra,1996). Greater corrosion inhibitive effect for the binary system wasobserved at 200 ppm ascorbic acid in combination with pectin atroom temperature. The inhibitory effect was due to the forma-tion of protective complex at the tin/solution interface. Resultsfrom potentiodynamic polarization technique showed that theinhibitive action of the system affected only the cathodic process,indicating that the pectin/ascorbic acid binary system was cathodictype inhibitor. Like other carbohydrate biopolymers, pectin can bemodified for many applications by carefully altering its functionalchemistry. With some anticorrosive polymers, structural modifi-cations improves the overall material performances by couplingsingle or multiple adsorption sites capable of metal surface bond-ing and physically displacement of corrosive molecules like wateracross the metal/solution interface. For mild steel inhibition in3.5 wt% NaCl solution, pectin has been grafted to polyacrylamideand polyacrylic acid, and the final materials protected steel morethan 85% (Geethanjali, Ali, Sabirneeza, & Subhashini, 2014). Thegraft polymerization procedure slightly differs from those reportedby Mishra, Sutar, Singhal, and Banthia (2007), except for modifica-tion in the final pH sensitive hydrogel products with acrylic andacrylamide acids, and pectin still used as precursors. Polymer syn-thesis and modification were followed by corrosion testing usingEIS and Tafel polarization, and then surface analytical evaluations(with FTIR and SEM) of the protective film formed on the steelsurface. Pectin modification products have also been reported asbeing used as antiscalants for water treatment (Chauhan et al.,2012). This procedure was only designed to lower the molecularweight of pectin by acid hydrolysis before grafting to acrylamide,thereby making copolymer-graft with an antiscalant potential forcarbonates, sulfates and phosphates. The outcome of the scalingremediation experiment with the final hydrolyzed pectin-basedgrafted material was outstanding against the carbonates precipita-tion, but this reaction was temperature and pH independent. SEM
and XRD techniques were employed in studying the precipitates’crystal morphology.

hydrat

2

idfifoatosaswasbgctocuabdbohfGsuemtm

2

rsfsdmaonSMCtbr

S.A. Umoren, U.M. Eduok / Carbo

.5. Pectate

Pectic acid (or polygalacturonic acid), like pectin is also presentn plants, but dominantly in ripened fruits (Sakai et al., 1993). Itserivatives, particularly pectates, obtained from structural modi-cation of pectin and pectic acid, could be better emulsifying and

oaming agents for food and medical industries. Pectates are saltsr esters of pectic acid. Hromádková, Malovikova, Mozes, Sroková,nd Ibringerová (2008) have reported the synthesis of some pec-ates (pectate alkyl amides) from citrus pectin via alkylamidationf esterified pectin from this source, followed by alkaline hydroly-is. These pectate amides were also tested for their foam stabilizingbilities. Schweiger (1962) has reported some routes for the sub-titution at hydroxyl groups of pectic substances, like nitropectinithout the rigorous conventional catalyzed reaction involving

cetic anhydride or acetyl chloride in pyridine. Just like other pecticubstances, pectates have also been involved in corrosion inhi-ition in some media in a view to utilizing their free alcoholicroups for metal surface bonding. Zaafarany (2012) has reportedorrosion inhibition of pectates (with alginates) anionic polyelec-rolytes for Al in 4 M NaOH using chemical methods. The presencef pectate in solution of the electrolyte markedly reduced theorrosion rate of Al, and an inhibition efficiency (%�) magnitudep to 88% was recorded for 1.6% pectate in the solution of thelkaline electrolyte using weight loss technique. Corrosion inhi-ition was found to be inhibitor concentration and temperatureependent but the study was without an explanation of the possi-le corrosion inhibition mechanism, electrochemically or by meansf kinetics/thermodynamic modelling. Recently, Zaafarany’s groupas revisited this work using sodium alginate and sodium pectate

or pure Al substarte in the same corrodent (Hassan, Zaafarany,obouri, & Takagi, 2013; Hassan & Zaafarany, 2013). The corre-ponding magnitudes of corrosion rate derived from the techniquessed in this study were computed and showed negligible differ-nce. Corrosion inhibition by Na pectate was ascribed to physicalolecular adsorption with the mechanism elucidated by means of

hermodynamic and kinetic parameters. Pectate adsorption on theetal surface followed Langmuir and Freundlich isotherm models.

.6. Chitosan and substituted/modified chitosans

Chitosan is a hydrophilic carbohydrate polymer naturally occur-ing in chitin-rich exoskeletons of marine crustaceans and inhrimps and crabs, and can also be extracted by N-deacetylation ofungal cell-wall chitin via alkaline treatment as well as chitins fromimple arthropods. It is being widely used against skin infectionsue to its antibacterial and fungal properties, and as drug-carriers inodern therapeutics (https://en.wikipedia.org/wiki/Chitosan). The

ntibacterial activities of chitosan as well as its combination withther polymers have been studied for a range of Gram-positive andegative bacterial infections (Rabea, Badawy, Stevens, Smagghe, &teurbaut, 2003; Gabriel, Tiera, & Tiera, 2015; Aziz, Cabral, Brooks,oratti, & Hanto, 2012; Chung, Yeh, & Tsai, 2011; Feng et al., 2014).

hitosan is also employed in the textile, paper and food indus-ries for various applications. Chitosan’s anticorrosion ability coulde drawn from its molecular structure (Fig. 5); it bears electron-ich hydroxyl and amino groups capable of steel metal surface

Fig. 5. Molecular structure of chitosan.

e Polymers 140 (2016) 314–341 325

bonding and subsequent corrosion inhibition via coordinate bond-ing as these electrons are donated to the empty or partiallyoccupied Fe orbitals. The grafting of these polar groups unto sur-faces increases total surface energy components thereby furtheraiding corrosion inhibition (Umoren, Banera, Garcia, Gervasi, &Mirıfico, 2013). Chitosan is a polysaccharide bearing �-(1-4)-linkedand N-acetyl-d-glucosamine units in its monomeric moiety.

Earlier reports on the corrosion inhibition of chitosan are thosepreviously reported in acid-induced conditions for copper and mildsteel (El-Haddad, 2013; Cheng, Chen, Liu, Chang, & Yin, 2007;Fekry & Mohamed, 2010; Mohamed & Fekry, 2011). Using chemicaland electrochemical techniques, the corrosion inhibition of copperhas been investigated in 0.5 M HCl using chitosan by El-Haddad(2013). Chitosan was revealed as being a mixed-type inhibitor inthe acidic condition from its unique Tafel behaviour. Electrochem-ical impedance results revealed steady decrease in double layercapacitance and increase in charge transfer resistance with increas-ing concentration of chitosan. Inhibition of copper corrosion in HClwas attributed to molecular adsorption of this biopolymer unto themetal surface, and this was approximated with Langmuir isothermand also evaluated with SEM and FTIR. Quantum chemical calcula-tions were also used to correlate the corrosion inhibition with themolecular structure of chitosan. Cheng et al. (2007) have reportedthe effectiveness of Carboxymethylchitosan-Cu2+ mixture for inhi-bition of mild steel in 1 M HCl using gravimetric (between 298and 353 K) and electrochemical techniques. Steel corrosion inhi-bition by this mixture was attributed to synergistic effect fromboth polymeric and ionic components; as individual componentsinhibited less than a combination of both. The magnitude of %�greater than 90% was obtained for Carboxymethylchitosan-Cu2+

mixture, with 86 and 14% obtained for 20 mg/L Carboxymethylchitosan and 0.01 ppm Cu2+, respectively. Corrosion inhibition ofmild steel in the presence of this mixture was also attributedmolecular adsorption of chitosan, and its inhibition mechanismwas further investigated with conductometry. Physical adsorp-tion mechanism was also proposed from thermodynamic/kineticsparameters. Fekry and Mohamed (2010) have reported the anti-corrosion ability of Acetyl thiourea chitosan conjugate polymer,synthesized by first preparing acetyl thiocyanate before addingto dissolve chitosan solution (in dimethyl formamide/acetic acidmixture at 100 ◦C). Using polarization and EIS techniques, cor-rosion studies with this chitosan-derived conjugate polymer wasconducted for mild steel in aerated 0.5 M H2SO4. Corrosion rateof mild steel greatly reduced in the presence of this conjugatepolymer but increased with temperature. Corrosion resistance wasfound to increase with immersion time, revealing that mild steelcorrosion inhibition by chitosan was due to molecular adsorp-tion on prolonged immersion. A %� value of 94.5% was obtainedfor 0.76 mM concentration of this conjugated biopolymer in thesolution of the acidic electrolyte. SEM was employed in study-ing the surface morphology of the steel substrate, in terms of theprevalence of deep localized pits and the formation of protec-tive film, in the absence and presence of inhibitor, respectively.Fekry and Mohamed (2010) have also reported the corrosion inhi-bition of chitosan-crotonaldehyde schiff’s base for AZ91E alloyinhibition in artificial sea water using EIS and Tafel techniques.Corrosion resistance in the saline solution was found to increasewith the immersion time and concentration of the schiff’s basebut decreased with temperature. AZ91E alloy corrosion inhibitionwas attributed to the adsorption of inhibitor films on the sur-face of the metal substrate, and this was confirmed by resultsfrom SEM. Chitosan-crotonaldehyde schiff’s base was also used to
adsorb Congo red dye and Maxilon Blue dyes, and its antimicrobialactivities were investigated against Escherichia coli, Staphylococcusaureus, Aspergillus niger and Candida albicans. Umoren et al. (2013)have investigated the role of a synthetically-derived chitosan in
https://en.wikipedia.org/wiki/Chitosan






3 hydrat

0atgIctwtaetse2ctattcfccTaccii

aspshese3tamwigafcstgtimcdpitrodhci


.1 M HCl for mild steel corrosion using chemical, electrochemicalnd surface analytical techniques. Corrosion inhibition was foundo increase with the concentration of chitosan, with values of %�reater than 90% recorded at low concentrations of the biopolymer.ts Tafel behaviour revealed a mixed-type inhibition for the range ofoncentrations studied. Authors attributed steel corrosion inhibi-ion to the formation of film at the surface of the substrate, and thisas confirmed by SEM and UV spectroscopy. Chitosan’s chemisorp-

ion at the metal surface followed Langmuir adsorption isotherm,nd kinetic/thermodynamic parameters were calculated to furtherxplain the mechanism of molecular adsorption. In another study,he anticorrosion properties of O-fumaryl-chitosan on low carbonteel has been investigated in aqueous HCl using weight loss andlectrochemical techniques (Sangeetha, Meenakshi, & Sundaram,015). Potentiodynamic polarization results revealed this modifiedhitosan biopolymer influenced both cathodic and anodic reac-ions, and recorded a 93% inhibition efficiency at 500 ppm. Forll the techniques employed in this study, the corrosion rate ofhe metal substrate reduced with the concentration of the chi-osan inhibitor. The trend in corrosion resistance and double layerapacitance with the concentration of the inhibitor was evaluatedrom the impedance results. Steel inhibition in the presence of thisompound was attributed to the film formation and adhesion ofomplexes at the surface of the metal via molecular adsorption.his was confirmed with surface analytical techniques (SEM, AFMnd FTIR), with the mechanism of inhibition proposed from electro-hemical findings including zero charge potential evaluation. Theorrosion mechanism was also evaluated by means of adsorptionsotherm plots and the assessment of the thermodynamics of thenhibition process.

More applications of modified chitosans and their compositeslso abound in the literature. Heptanoate anions have been encap-ulated into chitosan-modified beidellite coating for corrosionrotection of galvanized steel (Aghzzaf et al., 2012). The coatingystem was designed to initiate continuous releasing of inhibitingeptanoate molecules to the surface thereby healing any inher-nt micro-cracks. Diffuse reflectance infrared Fourier transformpectroscopy (DRIFTS), TG coupled MS and XRD techniques weremployed in studying the coating prior to corrosion test with EIS in

wt% NaCl for the coated galvanized steel. The steel corrosion pro-ection of this modified chitosan hybrid inhibitor was compared to

commercially available anticorrosive pigment (Triphosphate alu-inium). The improved corrosion inhibition for this class of coatingas attributed to leaching of hepatanoate ions at the metal/coating

nterface. Li, Li, Liu, and Huang (2015) have synthesized and investi-ated the anticorrosion properties of some methyl acrylate graftednd triethylene tetramine/ethylene diamine chitosan copolymersor Q235-grade carbon steel in 5% HCl at 25 ◦C for 72 h usinghemical and electrochemical techniques. The improved corro-ion inhibition of these hybrid chitosan systems was attributedo high chemical grafting; ethylene diamine chitosan copolymersave a 90% corrosion inhibition efficiency (%�) compared to theriethylene tetramine grafted system (%� = 85%). Steel corrosionnhibition was also attributed to the adsorption of grafted poly-

eric molecules to the surface of the metallic substarte; this wasonfirmed by metallographic microscopy and SEM. Thiocarbohy-razide graft chitosan has been synthesized and its anticorrosionroperties investigated against 304 steel and Cu sheet corrosion

n stagnant 2% acetic acid electrolyte containing the modified chi-osan inhibitor (Li et al., 2014a). Electrochemical polarization resulteveals the compound as a mixed type inhibitor with a magnitudef %� greater than 85% at concentration of 30 mg/L. Thiocarbohy-
razide graft chitosan was also used by authors to extract someeavy metal (As, Ni, Cu, Cd, Pb) ions up to an adsorption effi-iency of 60–99% at pH 9. Using the same metal substrates andn the same test electrolyte, authors have also investigated the
e Polymers 140 (2016) 314–341

corrosion inhibiting abilities of some thiosemicarbazide and thio-carbohydrazide modified chitosan derivatives (Li et al., 2014b).They were reported to be mixed-typed systems as well, and witha magnitude of %� greater than 90% at concentration of 60 mg/L.An adsorption efficiency of 60–99% for As, Ni, Cu, Cd, Pb ions atpH 9 was also reported for both compounds when employed asaqueous phase absorbents. Recently, Liu et al. (2015) have investi-gated the efficacy of �-cyclodextrin modified natural chitosan forcarbon steel corrosion in 0.5 M HCl using chemical and electro-chemical techniques. Corrosion inhibition was found to increasewith concentration of inhibitor at 30 ◦C. Potentiodynamic polar-ization results revealed this modified carbohydrate biopolymerinfluenced both cathodic and anodic reactions with magnitude of%� greater than 95%. Corrosion inhibition by this compound wasattributed to its molecular adsorption unto the metal surface, andthis was approximated with Langmuir adsorption isotherm alsoinvolving both physisorption and chemisorption protection mech-anism. Metal surface adsorption was confirmed with SEM/EDS.Chitosan films has also been involved in synthesis of protectivecoating for corrosion inhibition. In a recent report, chitosan hasbeen deposited on mild steel substrates by solution electrophore-sis via the application of a 15 V potential for 15 mins in a binarysolution of chitosan/acetic acid with glutaraldehyde employed asthe cross linker (Ahmed, Farghali, & Fekry, 2012). FTIR and SEMtechniques were employed for surface characterization of the filmafter electrodeposition before corrosion test using EIS and polariza-tion methods with the coated substrates immersed in 0.5 M H2SO4.Corrosion resistance of the chitosan coating was found to decreasewith immersion time in the solution of the electrolyte, and a %�value of 98% was obtained at the experimental condition understudy compared to bare steel. A self-healing chitosan-based hybridcoating doped with cerium (Ce) ions has also been synthesized foraluminium alloy AA 2024 (Zheludkevich et al., 2011). Ce ions servedas an encapsulated corrosion inhibitor in the bulk of the coat-ing thereby enhancing the material’s mechanical and protectivestrength. Optical microscopy, SVET, SEM/EDS and FTIR techniqueswere used in analyzing the undoped chitosan, and Ce-doped chi-tosan coating, before and after immersion in the solution of theelectrolyte after different exposure period in 0.05 M NaCl solution.EIS results reveal prolonged corrosion protection for the hybrid chi-tosan coating in the presence of Ce ions doped in the pre-layer of thecoating. Its self-healing ability at specific micro-confined defectswere assessed via localized electrochemical study. The protec-tive properties of Chitosan/Zn composite coating electrodepositedon mild steel from zinc sulphate/sodium chloride binary solutionhas been reported by Vathsala, Venkatesha, Praveen, and Nayana(2010). The effect of variation of principal electrolyte componentsas well as the concentration of Zn ions was investigated vis-à-vissuperior protection. Corrosion test was conducted in 3.5 wt% NaClfor this class of coating using chemical and electrochemical tech-niques, as well as salt spray test. The enhance corrosion protectionof this coating was attributed to synergistic inhibitive action ofZn ions in the coating, this was evident in the increased corrosionresistance in the presence of the Zn ions using EIS. SEM was alsoemployed in studying the surface morphologies and crystallinity inthe presence of chitosan. El-Sawy, Abu-Ayana, and Abdel-Mohdy(2001) have reported the synthesis of Poly(DEAEMA)-chitosan-graft-copolymer, poly(COOH)-chitosan-graft-copolymer, poly(V-OH)-chitosan-graftcopolymer, and carboxymethyl-chitosan for thecorrosion protection of steel panels uniformly coated at roomtemperature. Corrosion protection was reported to increase inmore highly grafted coatings, and their protection mechanism
was attributed to their bulk properties as well as the strengthof coating/metal bonding (adhesion). These compounds werealso used in adsorbing metals ions and dyestuffs from aqueoussolutions.


Table 3Typical examples of inhibition systems (involving pectic acid/pectin/pectates, chitosan and carrageenan) deployed for metal corrosion reduction in various aggressive media.



Reason for corrosioninhibition/corrosionreduction is attributed to thefollowing reason(s)

References

Pecticacid/Pectin/Pectate

1. Commercial pectinextracted from apple

Mixed type; butdominantlycathodic

X60 pipelinesteel/0.5 M HCl

Weight loss andpotentiodynamic polarizationtechniques, electrochemicalimpedance spectroscopy.Quantum chemical calculation(density functional theory(DFT)) results provide usefulinsights into the active sitesand reactivity parametersgoverning the corrosioninhibition with pectin

Corrosion inhibition wasattributed to the adsorptionand later formation ofprotective film on the metalsubstrate (confirmed byscanning electronmicroscopy, Fouriertransform infra-redspectroscopy and watercontact angle measurements)

Umoren et al.(2015b)

2. Pectin extracted fromcitrus peel

– Aluminium/0.5–2 MHCl

Weight loss technique Corrosion inhibition bypectin was attributed to itsadsorption on the metalsurface, thereby formingprotective film this wasconfirmed by scanningelectron microscopy

Fares et al.(2012a)

3. Pectin extracted fromfresh lemon peel

Mixed type Mild steel/1 M HCl Weight loss andpotentiodynamic polarizationtechniques, electrochemicalimpedance spectroscopy

Corrosion inhibition wascaused by geometric blockingeffect of chemisorbedinhibitive. Complex-typespecies at the metal surface.These pectin–Fe2+ ioncomplexes were formedduring the corrosion reaction(confirmed withspectroscopic (UV/V) andscanning electronmicroscopic analyses)

Fiori-Bimbiet al. (2015)

4. Pectin extracted fromtomato waste


Tin/2% NaCl, 1%acetic acid and 0.5%citric acid solution

Nuclear magnetic resonance,Fourier transform infra-redspectroscopic techniqueswere employed tocharacterize the pectinextracted and compared witha standard. Electrochemicalimpedance spectroscopy andpotentiodynamic polarizationtechniques were employed forthe corrosion test

Inhibitor molecularadsorption on the metalsurface

Grassino et al.(2016)

5. Pectin extracted fromcladodes of Opuntia ficusindica


Mild steel/1 M HCl Weight loss, potentiodynamicpolarization techniques,electrochemical impedancespectroscopy

Adsorption of the inhibitor’sorganic matter on the mildsteel surface; and theformation of protective filmat the metal/acid solutioninterface

Saidia et al.(2015)

6. Pectin [propylphosphonic acid andZn2+]

Mixed type Carbonsteel/60 ppmchloride solution

Weight loss, potentiodynamicpolarization techniques,electrochemical impedancespectroscopy

Corrosion inhibition wasattributed to the formation ofprotective film on the surfaceof the carbon steel in theneutral aqueous medium;Synergistic inhibition due tothe presence of pectin, alongwith propyl phosphonic acidand Zn2+; (confirmed withFourier-transform infraredspectroscopy, atomic forcemicroscopy, scanningelectron microscopy, andX-ray photoelectronspectroscopy). Authorssuggested that the protectivefilm must have consisted of[Fe3+)/Fe2+/Zn2+)–propylphosphonic acid–pectin]complex, Zn(OH)2, andhydroxides and oxides of iron

Prabakaranet al. (2015)


Table 3 (Continued)




References

7. Pectin–ascorbic acidbinary system

Cathodic type Tin/Neutral NaClsolution

Weight loss andpotentiodynamic polarizationtechniques

The inhibitory effect of thisinhibitor system wasattributed to the formation ofprotective complex at thetin/solution interface

Nada et al.(1996)

8.Pectin-g-polyacrylamideand Pectin-g-polyacrylicacid grafted polymers


Mild steel/3.5%NaCl

Pectin-g-polyacrylamide andPectin-g-polyacrylic acidgrafted polymers weresynthesized from pectin,acrylamide, and acrylic acid asprecursors. Characterizationof the synthesized graftedpolymer: Fourier transforminfrared spectroscopy (FTIR),thermogravimetric analyser(TGA), and scanning electronmicroscopy (SEM). Corrosiontest: Potentiodynamicpolarization techniques,electrochemical impedancespectroscopy, and thensurface analytical evaluations.

Inhibition was due theformation of protective filmon mild steel surface(confirmed with Fouriertransform Infra-redspectroscopy and scanningelectron microscopy

Geethanjaliet al. (2014)

9. Pectate (with alginate)anionic polyelectrolytes

– Aluminium/4 MNaOH


Corrosion inhibition wasattributed the chemicaladsorption via hydroxylgroups of the polymeranionic polyelectrolytesforming bridges between thepolymer and the metalsurface

Zaafarany(2012)

10. Sodium pectate (withsodium alginate)

– Aluminium/4 MNaOH


Same as Zaafarany (2012) Hassan et al.(2013)

11. Pectate anionicpolyelectrolyte

– Aluminium/1 MHCl


Same as Zaafarany (2012) Hassan andZaafarany(2013)

12. Calcium alginate gelcapsules loaded withImidazoline quaternaryammonium salt

– P110 steel/CO2

saturated 3.5 wt%NaCl

Ultraviolet–visiblespectrophotometry, scanningelectron microscopy,electrochemical impedancespectroscopy

Improved corrosioninhibition was attributed tothe gradual release of theimidazoline inhibitor at themetal/solution interface(surface adsorption wasconfirmed with scanningelectron microscopy)

Wang et al.(2015)

Chitosan andsubstituted/modifiedchitosans

13. Chitosan Mixed type Mild steel/0.1 MHCl

Weight loss, potentiodynamicpolarization techniques,electrochemical impedancespectroscopy

Chemical adsorption ofchitosan on the metal surfacewas concluded as the causeof corrosion inhibition(confirmed with surfaceanalytical techniques)

Umoren et al.(2013)

14. Chitosan Mixed type Copper/0.5 M HCl Weight loss, potentiodynamicpolarization techniques,electrochemical impedancespectroscopy andelectrochemical frequencymodulation techniques.Quantum chemicalcalculations was also used tocorrelate the corrosioninhibition with the molecularstructure of chitosan

Inhibition was due theformation of protective filmon mild steel surface(confirmed with Fouriertransform Infra-redspectroscopy and scanningelectron microscopy

El-Haddad(2013)

15. Carboxymethylchitosan–Cu2+

Mixed type Mild steel/1 M HCl Weight loss, potentiodynamicpolarization techniques,electrochemical impedancespectroscopy

Corrosion inhibition of mildsteel in the presence of thismixture was attributedmolecular adsorption ofchitosan, and its inhibitionmechanism was furtherinvestigated withconductometry

Cheng et al.(2007)


Table 3 (Continued)




References

16.Acetyl–thiourea–chitosanconjugate polymer

Mixed type Mild steel/0.5 MH2SO4

Potentiodynamic polarization,electrochemical impedancespectroscopy

Scanning electronmicroscopy was deployed tostudy the surfacemorphology of the steelsubstrate, in terms of theprevalence of deep localizedpits and the formation ofprotective film, in theabsence and presence ofinhibitor, respectively

Fekry andMohamed(2010)

17.Chitosan–crotonaldehydeschiff’s base

Mixed type AZ91Ealloy/Artificial seawater

Potentiodynamic polarization,electrochemical impedancespectroscopy

Corrosion inhibition wasattributed to inhibitormolecular adsorption at themetal surface

Mohamed andFekry (2011)

18. Heptanoate anionsencapsulated into achitosan–modifiedbeidellite coating

– Galvanizedsteel/3 wt% NaCl

Electrochemical impedancespectroscopy. Diffusereflectance infrared Fouriertransform spectroscopy(DRIFTS), TG coupled MS andXRD techniques

The improved corrosioninhibition for this class ofcoating was attributed toleaching of hepatanoate ionsat the metal/coatinginterface, thereby preventingthe further passage ofcorrosive chloride ionstowards the metal surface

Aghzzaf et al.(2012)

19. Synthesized methylacrylate grafted andtriethylenetetramine/ethylenediamine chitosancopolymers

Cathodic type Carbon steel(Q235-grade)/5%HCl

Weight loss, potentiodynamicpolarization technique,electrochemical impedancespectroscopy

Corrosion inhibition wasattributed to the dense“sustained-release” nature ofthe film on the electrodesurface (confirmed byscanning electronmicroscopy)

Li et al. (2015)

20. Thiocarbohydrazidegraft chitosan

Mixed type 304 steel/Coppersheets/2% aceticacid

Charaterization of the inhibitor:Fourier transform infraredspectroscopy, elementalanalysis, thermal gravityanalysis and differentialscanning calorimetry, Corrosiontest: Potentiodynamicpolarization

Corrosion inhibition wasattributed to the formation ofprotective film formed on thesteel surface (confirmed byscanning electronmicroscopy)

Li et al. (2014a)

21. Thiosemicarbazide andthiocarbohydrazidemodified chitosanderivatives

Mixed type Same as Li et al.(2014a)

Same as Li et al. (2014a) Same as Li et al. (2014a) Li et al. (2014b)

22. �-Cyclodextrinmodified naturalchitosan

Mixed type Low carbonsteel/0.5 M HCl

Weight loss, potentiodynamicpolarization technique,electrochemical impedancespectroscopy

Corrosion inhibition wasattributed to inhibitormolecular adsorption andthe formation of protectivefilm on the metal surface(confirmed with scanningelectron microscopy)

Liu et al. (2015)

23. Chitosan deposited onmild steel substrates bysolution electrophoresisvia the application of a15 V potential for 15mins in a binary solutionof chitosan/acetic acidwith glutaraldehydeemployed as the crosslinker

Coating caused ahuge displacementin both redoxcurrents(Mixed-type)

Coated mild steelsubstrates/0.5 MH2SO4

Fourier transform infra-redspectroscopic and scanningelectron microscopic techniqueswere employed for surfacecharacterization of the film afterelectrodeposition and beforecorrosion test. Corrosion test:Potentiodynamic polarizationtechnique, electrochemicalimpedance spectroscopy

Corrosion inhibition wasattributed to the barriertowards the passage ofcorrosive sulphate ionsthrough the protective filmcoating on the metal surface(the surface morphology ofthe coating was conductedwith scanning electronmicroscopy)

Ahmed et al.(2012)

24. Self-healingchitosan-based hybridcoating doped withcerium ions (corrosioninhibitors)

– Aluminium alloy(AA 2024grade)/0.05 M NaCl

Optical microscopy, SVET,scanning electronmicroscopy/Energy dispersiveX-ray and Fourier transforminfra-red spectroscopictechniques were used inanalyzing the undoped chitosan,and Ce-doped chitosan coating,before and after immersion inthe solution of the electrolyteafter different exposure periodin 0.05 M NaCl solution.Corrosion test: Electrochemicalimpedance spectroscopy

The encapsulated Ce ionsserved as corrosioninhibitors in the bulk of thecoating thereby enhancingthe coating material’smechanical and protectivestrength; and also to offeredthe needed self-healingability by specific microcracksites

Zheludkevichet al. (2011)


Table 3 (Continued)




References

25. Chitosan/Zn compositecoating electrodepositedon mild steel from zincsulphate/sodiumchloride binary solution

– Mild steel/3.5 wt%NaCl

Weight loss and potentiodynamicpolarization technique,electrochemical impedancespectroscopy; salt spray test

Corrosion inhibition wasattributed to the barrier ofcorrosive ions from passingthrough the protective filmcoated on the metal surface(confirmed with scanningelectron microscopy). Theenhanced corrosionprotection for this coatingwas concluded as being dueto the presence of Zn2+ ionsin the coating

Vathsala et al.(2010)

26. Chitosan graftednanogels

Superior barriercharacteristicswere attributed toinhibition of bothcathodic andanodic reactions(Mixed type)

Mild steel/1 M HCl Potentiodynamic polarizationtechnique and electrochemicalimpedance spectroscopy

Corrosion inhibition of thisnanogel was attributed to theformation of activeprotective film carryingchitosan molecules at themetal/solution interface(confirmed with scanningelectron microscopy)

Atta et al.(2015)

27. Nanostructuredchitosan/ZnOnanoparticles

Cathodic type Mild steel/0.1 N HCl Potentiodynamic polarizationtechnique, electrochemicalimpedance spectroscopy

Improved metal surfaceprotection was revealed forcompacted films in thepresence of ZnO, and theformation of nanofilms onsteel was concluded as theprincipal cause of corrosioninhibition of steel, and thiswas characterized withUV–vis, Fourier transforminfra-red spectroscopy, X-raydiffraction and scanningelectron microscopy/EnergyDispersive X-rayspectroscopy

John et al.(2015)

28. Chitosan (shrimp shellwaste) modified to aswater soluble chitosanderivatives(2-N,N-diethylbenzeneammonium chlorideN-oxoethyl chitosan and12-ammonium chlorideN-oxododecan chitosan)

– Carbon steel/1 MHCl

Weight loss technique Corrosion inhibition wasreported as being initiated bythe changes in theorientation of substitutedgroups and the degree ofoverlapping ofintra-hydrogen bondingwithin the same molecule.Molecular adsorption ofchitosan on the metal surfacewas concluded as the solecause of steel corrosioninhibition

Hussein,El-Hady,Shehata,Hegazy, &Hefni (2013)

29. Carboxymethylchitosan–benzaldehydeand carboxy methylchitosan–urea–glutaricacid

– Mild steel/2% NaCl Fluidization Corrosion inhibition wasattributed to molecularadsorption of the inhibitorson the metal surface

Suyanto, Ratih,& Leo (2015)

30.Mercaptobenzothiazole-controlled releasechitosan–based coating

– Aluminum alloy(AA 2024grade)/0.05 M NaCl

Electrochemical impedancespectroscopy

The improved corrosioninhibition for this class ofcoating was attributed toleaching ofmercaptobenzothiazole atthe metal/coating interface

Carneiro et al.(2013a),Carneiro et al.(2013b)

31. Chitosan coatingsdoped with ceriumnitrate

– Aluminum alloy(AA 2024grade)/0.05 M NaCl

Electrochemical impedancespectroscopy

It was observed that thechitosan layer worked as areservoir for cationic Ce3+

corrosion inhibitor due to thecomplexation of Ce3+ withchitosan amino groups,which prevented itsuncontrollable and fastleaching

Carneiro et al.(2012)

32. Modified chitosansurfactants

Mixed type API 65 pipelinesteel/1 M HCl

Potentiodynamic polarizationtechnique. Quantum chemicalcalculations was also used tocorrelate the corrosion inhibitionwith the molecular structure ofchitosan

Corrosion inhibition wasattributed to molecularadsorption of the inhibitorson the metal surface

Alsabagh et al.(2014)


Table 3 (Continued)




References

33. N-(2-hydroxy-3-trimethylammonium)propylchitosan chloride

Cathodic type Mild steel/1 M HCl Weight loss and potentiodynamicpolarization technique,electrochemical impedancespectroscopy

Corrosion inhibition wasattributed to its adsorption onthe metal surface, therebyforming protective film(confirmed with Fouriertransform infra-redspectroscopy and scanningelectron microscopy)

Sangeetha et al.(2015)

34. O-fumaryl-chitosan Mixed type Mild steel/1 M HCl Weight loss and potentiodynamicpolarization technique,electrochemical impedancespectroscopy

Corrosion inhibition wasattributed to its adsorption onthe metal surface, therebyforming protective film(confirmed with Fouriertransform infra-redspectroscopy and scanningelectron microscopy, X-raydiffraction and Atomic forcemicroscopy)


35. Layer-by-layerchitosan/poly vinylbutyral coating

– Mild steel/0.3 Maerated NaClsolution

Electrochemical (EIS andpotentiodynamic) and surfaceanalytical (SEM and Ramanspectroscopy) techniques

Barrier protection by thiscoating was attributed to thechitosan middle layersandwiched between polyvinyl butyral bilayers on themetal substrate, as well as theincorporating glutaraldehydewithin the chitosan layer.Formation of passive oxidelayer (Fe3O4 and �-Fe2O3

oxide)

Luckachan andMittal (2015)

Carrageenan35. i-carrageenan – Aluminium/2 M

HClWeight loss technique Scanning electron microscope

demonstrated smooth, glossy,and relatively coherentadsorption layers of theinhibitor on the metal surfacein aqueous solution

Fares et al.(2012a, 2012b)

36. i,k,�-carrageenan Anodic type Low carbon Weight loss and galvanostaticpolari

Corrosion inhibition was Zaafarany

tfAtwasrraCtCtirbpiJniEpa

steel/1 M HCl

The modification of chitosan molecules also involves the syn-heses of its nanoparticle composites for metal protection, and aew of them has been reported in the literature. Atta, El-Mahdy,l-Lohedan, and Ezzat (2015) have synthesized hydrophobic chi-

osan nanogels with unsaturated fatty acids before grafting themith polyoxyethylene aldehyde monomethyl ether to prepare

mphiphilic chitosan surfactant (ACS). Nanoscaled particles of thisurfactant were later made from emulsification and crosslinkingeactions using methylene chloride with sodium tripolyphosphate,espectively. Hydrophobicity, functional group and particle sizenalyses were carried out using appropriate analytical techniques.haracterization of the grafted nanoparticles was followed by elec-rochemical corrosion tests using EIS and Tafel methods. Values ofdl decreased while the corrosion resistance of carbon steel elec-rode was found to increase with the concentration of the nanogeln the HCl (1 M) electrolyte, with values of %� greater than 85%ecorded at a nanoscale concentration of 250 mg/L. Corrosion inhi-ition of this nanogel was attributed to the formation of activerotective film carrying chitosan molecules at the metal/solution

nterface; this was further confirmed by SEM analysis. John, Joseph,ose, and Narayana (2015) have also reported the synthesis ofanostructured chitosan/ZnO nanoparticles by sol–gel method, and

ts anticorrosion ability evaluated electrochemically by Tafel andIS techniques for mild steel in 0.1 N HCl. Improved metal surfacerotection was revealed for compacted films in the presence of ZnO,nd this further enhanced increased values of inhibition efficiency

zation techniques attributed to the blocking thesteel surface by carrageenans’molecular adsorption

(2006)

(%� > 70% and <40% was obtained in the presence and absence ofZnO, respectively). Formation of nanofilms on steel was concludedas the principal cause of corrosion inhibition of steel, and this wascharacterized with UV–vis, FTIR, XRD and SEM/EDX. Luckachan andMittal (2015) have recently reported the protective of layer-by-layer chitosan/poly vinyl butyral coating on steel investigated usingelectrochemical, spectroscopic and SEM. This corrosion resistantproperty of this hybrid coating was evaluated after 2 h immersionin 0.3 M NaCl, with the formation of passive oxide layer (Fe3O4and �-Fe2O3 oxide) on the metal substrate confirmed by SEM andRaman spectroscopy. Barrier protection by this coating was foundto improve due to the chitosan middle layer sandwiched betweenpoly vinyl butyral bilayers on the metal substrate, as well as theincorporating glutaraldehyde within the chitosan layer. This wasnot observed with graphene and vermiculite incorporated with thesame chitosan matrix in the same condition. Other anticorrosionapplications involving pectic acid/pectates and modified chitosansand their composites reported in the literature are presented inTable 3.

2.7. Carrageenan

Carrageenan is a group of gel-like and mostly linear polysac-charides bearing sulfated �-d-galactose and 3,6-anhydro-�-d-galactose backbone and commonly found in seaweeds (family:


Rtetsefrsbhc3tlbtc(briccoaerit(bptectctpt(intiCfiiiai

Fig. 6. Molecular structures of carrageenan repeat unit.

hodophyceae). Fig. 6 displays the molecular structure (iota),hough other structures (e.g. Mu, Kappa, Nu, Lambda forms) doxist in nature. Carrageenan can also be classified according tohe degrees of linear chain sulfation as well as the degree of theubstitution occurring at the free hydroxyl groups on the lin-ar polysaccharide chain. Their molecular symmetry is flexible,orming unstable helical conformations, thereby making most car-ageenans exist as gels at room temperature. This unique physicaltructures aids in their application as food thickeners and sta-ilizers (van de Velde & DeRuiter, 2005). Nanaki et al. (2015)ave reported the synthesis of modified carrageenans at differentoncentrations for aqueous state Metoprolol ((1-(isopropylamino)--[4-(2-methoxyethyl)phenoxy]propan-2-ol)) removal at roomemperature. The kinetics of carrageenan oxidation (iota andambda forms) by permanganate in perchlorate solutions have alsoeen reported by Hassan et al. (2011). In the same acidic solu-ion, this group has also investigated the effect of hydrogen iononcentrations on chromic acid oxidation rate of k-carrageenanZaafarany, Khairou, & Hassan, 2009). Carrageenans are green andiodegradable carbohydrate polymers with the potentials for cor-osion protection just like other carbohydrate polymers discussedn this series. They are benign and due to their unique chemi-al structures and functional groups, they possess the ability ofomplexing ions of metals at surfaces, thereby inhibiting aque-us corrosion. The sulphonic acid groups on these biopolymersre endowed with �-orbital character of donating electron to thempty 3d orbital of the Fe substrates. The investigation of the cor-osion inhibition potential of i-carrageenan for aluminium sheetsn presence of a mediator has been reported using weight lossechnique after 2 h immersion in different concentrations of HCl1.0–2.0 M) (Fares, Maayta, & Al-Qudah, 2012b). Al corrosion inhi-ition by i-carrageenan was found to improved greatly in theresence of pefloxacin mesylate (inhibition mediator); magni-ude of %� increasing from 66.7% to 91.8%. This metal inhibitionnhancement was attributed to the synergistic adsorption of i-arrageenan/pefloxacin mediator compact film on the surface ofhe metal (Al). This was confirmed by SEM analysis, while theorrosion inhibition mechanism by molecular adsorption was fur-her explained with kinetics and thermodynamics evaluation in theresence of the inhibitor and mediator. Inhibitor molecular adsorp-ion followed Langmuir adsorption isotherm model. Zaafarany2006) has also studied the corrosion inhibition of low carbon steeln 1 M HCl using weight loss and galvanostatic polarization tech-iques with i, k, �-carrageenan. Corrosion inhibition was foundo decrease with increase in temperature but increased with thencrease in concentration of these polysaccharide biopolymers.orrosion inhibition was attributed to the blocking the steel sur-ace by carrageenans’ molecular adsorption. The adsorption of thenhibitors on the metal substrate followed Langmuir adsorptionsotherm. These compounds were revealed as being anodic-type
nhibitors for steel in the acidic medium studied, and kineticsnd activation thermodynamic parameters were computed to addnsights into the corrosion inhibition mechanism.
Fig. 7. Molecular structure of dextrin.

2.8. Dextrin and cyclodextrins

Dextrin is a class of low molecular weight carbohydrate poly-mers structurally characterized by glucose (D) units linked byglycosidic bonds [�-(1 → 4) or �-(1 → 6)]; Fig. 7. They occur nat-urally in the human digestive system via amylases catalyzedstarch hydrolysis in the human mouth; it can also be synthe-sized by heat treatment in acidic solutions (https://en.wikipedia.org/wiki/Dextrin). Various forms of dextrin exist in nature rangingfrom maltodextrin, amylodextrin, �,�-dextrin, cyclic and highlybranched cyclic dextrin compounds. Apart from being employedas food additives and in brewing, short chain dextrin as well as thehighly branched cyclic derivatives have been deployed as corrosioninhibitors in various corrosive media (Jayalakshmi & Muralidharan,1997); earlier researches date back between the late 1970s andthe early 1980s for titanium and aluminium/copper alloys, respec-tively (Shibad & Balachandra, 1976; Patel, Pandya, & K, 1981; Talati& Modi, 1976).

Loto and Loto (2013) have reported the effect of dextrin andthiourea additives on the corrosion of steel (low carbon grade) afterelectroplating the surface with zinc by applying negative potentialbetween with a zinc electrode connected to the steel test sub-strate in ZnCl2 solution. The corrosion test was conducted in anacid chloride electrolyte. The electroplating procedure revealeddensely packed zinc crystals on steel without pores but the sub-strates possessed different surface morphologies for every platingperiod under study. Dextrin in combination with thiourea additivedemonstrated remarkable superior protection at the highest plat-ing period compared to the rest of the matrices as examined bySEM/EDS. The anticorrosion properties of �-cyclodetrin-modifiedacrylamide polymer have been investigated in 0.5 M H2SO4 forX70 steel grade by electrochemical and surface analytical tech-niques. Potentiodynamic polarization results revealed that thismodified carbohydrate influenced both cathodic and anodic reac-tions with a magnitude of %� greater than 84.9% for 150 mg/l at303 K. Adsorption of the hybrid polymer on metal surface fol-lowed Langmuir adsorption isotherm and corrosion inhibition wasexplained by means of thermodynamic and kinetics parameters.Corrosion inhibition was attributed to molecular adsorption at themetal surface, confirmed by SEM/EDS (Zou, Yan, Qin, Wang, & Liu,2014a). Zou et al. (2014b) have investigated the efficacy of bridged�-cyclodextrin-polyethylene glycol (�-DP) for Q235 carbon steelin 0.5 M HCl using chemical and electrochemical techniques. �-DP was characterized by FTIR reacting after being synthesizedvia a reaction between �-cyclodextrin with polyethylene glycol.Tafel polarization curves revealed that this hybrid biopolymer wasa mixed type inhibitor compound in the solution of the elec-trolyte while corrosion inhibition was attributed to the formationof protective �-DP film at the surface of the metal; this was con-firmed by SEM/EDX. Recently, authors have also reported the scaleinhibition using �-DP composite for produced-water in shale gaswell with up to 89.1% maximum scaling inhibition efficiency for180 mg/l (Liu, Zou, Li, Lin, & Chen, 2016). Yan, Zou, and Qin (2014)have reported the effectiveness of polyacrylamide modified �-
cyclodextrin composite for inhibition of X70 steel corrosion in in0.5 M H2SO4 using electrochemical and chemical methods and sur-face analytical techniques. Corrosion inhibition in the presence
https://en.wikipedia.org/wiki/Dextrin






hydrat

obdatmiceg0apa2taiwtocsanctasipTf

2

nsgftdbsfatas

fw(oSa


f this composite was found to increase with its concentrationut not with temperature while the trend in Tafel polarizationata revealed that polyacrylamide/�-cyclodextrin composite was

mixed type inhibitor system. Corrosion inhibition was attributedo molecular (chemisorption) adsorption of this composite on the

etal surface and the adsorption phenomenon followed Langmuirsotherm. SEM results revealed the formation of polyacrylamide/�-yclodextrin composite protective film on X70 steel surface. Liut al. (2015) have studied the anticorrosion properties of chitosan-rafted �-cyclodextrin composite for carbon steel corrosion in.5 M HCl using weight loss, potentiodynamic polarization, EISnd SEM/EDS techniques. DC polarization curves reveal that theresence of this inhibitor composite affected both cathodic andnodic reaction with 96.02% as the highest inhibition efficiency at30 ppm. Corrosion inhibition of carbon steel in the presence ofhis composite was also attributed to molecular adsorption, and itsdsorption process was approximated with Langmuir adsorptionsotherm. Physisorption/chemisorption adsorption mechanism

as also proposed from the variation in thermodynamic parame-ers. Fan, Wei, Zhang, and Qiao (2014) have reported the synthesisf hydroxypropyl-�-cyclodextrin/octadecylamin supramolecularomplex with anticorrosion properties for Q235A steel. Corrosiontudy was conducted in CO2 saturated deionized water (at 5.6 pH)t room temperature using chemical and electrochemical tech-iques after the characterization of the synthesized supramolecularomplex with FTIR, XRD and NMR spectroscopy. Corrosion inhibi-ion efficiency of 95% was obtained for the synthesized complexnd the inhibition process was attributed to the formation of pas-ive inhibitor layer as well as hydrophobic octadecylamin inherentn the supramolecular complex at the metal surface. The com-lex acted predominantly anodic than cathodic from the trend ofafel polarization results with 90% inhibition efficiency obtainedor 50 mg/l complex.

.9. Alginates

This acid-type anionic polysaccharide is the principal compo-ent in the colloidal gum found in the cell walls of algae andeaweeds where it binds with molecular water. Alginate is aroup of sugars also called alginic acid (due to the carboxylic acidunctional group attached to their molecular structure) or algin;hey are linear copolymers with covalently bound (1-4)-linked �--mannuronate and C-5 epimer �-l-guluronate homopolymericlocks (Fig. 8). Alginates have numerous forms depending on theiralts (principally alkaline or alkaline salts). Na alginate extractsrom brown seaweeds are widely deployed as dental gelling agents,nd their usage is common in pharmaceutical as well as food indus-ries. K and Ca alginates are used as industrial alternatives to Nalginates while the organic forms of this compound have also beenynthesized with various applications.

Alginates have also been widely reported as corrosion inhibitorsor various metals in different media, and one of the earliest reportsith regards to alginate is the one by the Desai’s in the late 1970s

Desai & Desai, 1970) where the effect of Na alginate on the cath-de and anode potentials of A1-3S in 0.2 N NaOH was evaluated.riram, Sadhir, Saranya, and Srinivasan (2014) have studied thenticorrosion properties of Na alginate extracts from a brown

Fig. 8. Molecular structure of alginate.

e Polymers 140 (2016) 314–341 333

seaweed (Turbinaria ornate) for aluminium alloy (AA 7075 grade)in 3.5 wt% NaCl using potentiodynamic polarization technique. Thisextract was found to inhibit aluminium corrosion to a great extent,with 95% inhibition efficiency obtained at 2000 ppm after 24 h.Authors attributed this to the adsorption of inhibition-inducingfunctional groups found on the extract; this was also confirmedwith FTIR spectroscopy. This compound has also been reported forcarbon steel corrosion in 0.5 M HCl investigated by chemical andelectrochemical techniques (Al-Bonayan, 2014). Corrosion inhibi-tion was found to increase with the concentration of Na alginatebut not with temperature; this was attributed to the adsorptionof sodium alginate at the metal surface. Molecular adsorption wasexplained by means of isotherm and activation parameters derivedfrom results of the chemical technique, while the effect of con-centration of the inhibitor on the charge transfer resistance andcapacitance of double layer was also explained. Zaafarany (2012)have also reported the application of alginate (apple derived)-anionic polyelectrolytes as corrosion inhibitors for pure aluminumin 4 M NaOH at 25 ◦C using gravimetric and gasometric tech-niques. A corrosion inhibition efficiency of 86.66% was recordedfor 1.6% alginate at 30 ◦C in the alkaline test solution. Al corrosionreduction in this medium was attributed to the unique functionalchemistry on the inhibitor, and the mechanism of inhibition wasexplained in terms of kinetic and thermodynamic parameters.Deployed for magnesium test substrate (AZ31 alloy grade), Na algi-nate have also been recently studied by another group of authorsin 3.5 wt% NaCl (Dang, Wei, Hou, Li, & Guo, 2015). They found thatcorrosion inhibition increased with concentration of Na alginatethough a decrease in magnesium protection was also observedafter prolonged immersion in the solution of the inhibitor. A cor-rosion inhibition efficiency of 90% was obtained for 500 ppm Naalginate, and this was attributed to molecular adsorption and sub-sequent formation of compact film (freshly generated magnesiumhydroxide) on the metal surface. Tawfik (2015) has synthesizedand appropriately characterized alginate surfactant derivativesfor anticorrosion application. These surfactants were deployed ascorrosion inhibitors for carbon steel in 1 M HCl using chemical,electrochemical and surface analytical techniques. Corrosion inhi-bition increased with the concentration of these compounds andwith temperature, with a 96.27% inhibition efficiency obtained for5 mM alginate derived cationic surfactant complexed with copper.Tafel curves revealed that these inhibitors were mixed type thoughpredominantly cathodic. Parameters derived from thermodynamicand activation evaluations of the trend in experimental results wereemployed to investigate the inhibition mechanism. Wang et al.(2015) have recently investigated the anticorrosion properties ofCa alginate gel loaded with imidazoline quaternary ammoniumsalts; this composite was prepared by piercing-solidifying methoddesigned to automatically release these imidazoline corrosioninhibitors at the metal surface (P110 steel) immersed in CO2-saturated 3.5 wt% NaCl medium. Corrosion studies were conductedby EIS while UV–vis spectroscopy and SEM complemented theelectrochemical technique as surface analytical techniques. Thisauto-release inhibition type system was effective to a great extentas the corrosion inhibitors were released from the gel as it swells inthe solution of the corrosive electrolyte. BaSO4 was also encapsu-lated within alginate/imidazoline composite in order to aid sinkingand improved corrosion retardation was well. Hydroxyl propyl algi-nate, an organic type alginate derivative, have been deployed toreduce mild steel corrosion in 1 M HCl at room temperature usingchemical and electrochemical techniques. Corrosion inhibition wasfound to increase with the concentration of this compound due
to molecular (physisorption) adsorption at the metal surface; con-firmed by SEM, AFM and FTIR as adsorbed film. Results from Tafelpolarization revealed that corrosion inhibition in the presence ofthis compound affects both anodic and cathodic reactions. Inhibitor


Table 4Examples of inhibition systems (involving dextrin, alginates and their derivatives) deployed for metal corrosion reduction in various aggressive media.



Reason for corrosioninhibition/corrosionreduction is attributed tothe following reason(s)

References

Dextrin1. Dextrin (including acacia,

gelatin, agar and glue)Neither cathodenor anode werepredominantlypolarized

Al/Cualloy/0.1–1.0 N HCl

Weight loss andpotentiodynamicpolarization techniques

Corrosion inhibition wasattributed to theadsorption and theformation of protectivefilm on the metal

Patel et al.(1981)

2. Dextrin (in the presence ofFe+3,Cu+2 and Ni+2)

– Titanium andtitanium alloy/20%HC1 and H2SO4

Open circuit potentialmeasurements

Corrosion inhibition wasattributed to theadsorption at the metalsurface

Shibad andBalachandra(1976)

3. Dextrin (including acacia,gelatin, agar agar, tragacanthand glue)

– Aluminium-copperalloy/0.1-1 M NaOH

Weight loss Corrosion inhibition wasattributed to theadsorption at the metalsurface

Talati and Modi(1976)

Dextrin and Thiourea – Dextrin andThiourea Additiveson the ZincElectroplated MildSteel/acid chlorideelectrolyte

Adhesion test andSEM/EDS

The electroplatingprocedure revealeddensely packed zinccrystals on steel with nopores with differentsurface morphology foreach plating period understudy. Dextrin incombination with thioureaadditive demonstratedremarkable superiorprotection at the highestplating period compared tothe rest of the matrices asexamined by SEM/EDS

Loto and Loto(2013)

4. �-Cyclodextrin-modifiedacrylamide polymer

Mixed typeinhibitor system

X70 steel/0.5 MH2SO4

Potentiodynamicpolarization, EIS andSEM coupled with EDS

Corrosion inhibition wasattributed to the molecularadsorption on the metalsurface

Zou et al.(2014a)

5. �-cyclodextrinepolyethyleneglycol


Q235 carbonsteel/0.5 M HCl

EIS, potentiodynamicpolarization andweight loss techniques


Zou et al.(2014b)

6. Polyacrylamide modified�-cyclodextrin composite


X70 steel/0.5 MH2SO4

Weight loss,Potentiodynamicpolarization, EIS andSEM


Yan et al.(2014)

7. Hydroxypropyl-b-cyclodextrin/octadecylaminsupramolecular complex

Mixed typeinhibitor system(but predominantlyanodic thancathodic)

Q235A steel/CO2

saturateddeionized water at5.6 pH

EIS andpotentiodynamicpolarization

Corrosion inhibition wasattributed to the formationof passive inhibitor layer aswell as hydrophobicoctadecylamin inherent inthe supramolecularcomplex at the metalsurface

Fan et al.(2014)

8. Chitosan-grafted�-cyclodextrin composite


Carbon steelcorrosion/0.5 MHCl

Weight loss,potentiodynamicpolarization, EIS andSEM/EDS techniques

Corrosion inhibition ofcarbon steel in thepresence of this compositewas also attributedmolecular adsorption ofthe composite

Liu et al. (2015)

Alginate9. Na alginate – A1-3S in 0.2 N

NaOHAnodization/anodicand cathodicpolarization

Molecular adsorption Desai and Desai(1970)

10. Na alginate extracts from abrown seaweed (Turbinariaornate)


aluminium alloy(AA 7075 grade) in3.5 wt% NaCl

Potentiodynamicpolarization technique

Authors attributedcorrosion inhibition toadsorption of functionalgroups found on thealginate extract; this wasalso confirmed with FTIRspectroscopy

Sriram et al.(2014)

11. Na alginate Carbon steelcorrosion/0.5 MHCl

Weight loss,potentiodynamicpolarization, EIS andelectrochemicalfrequency modulation(EFM)

Molecular adsorption atthe metal surface

Al-Bonayan(2014)


Table 4 (Continued)



Reason for corrosioninhibition/corrosionreduction is attributed tothe following reason(s)

References

12. Apple derivedalginate-water-soluble naturalpolymer anionicpolyelectrolytes (includingpectate)

– Purealuminum/4 MNaOH

Gravimetric andgasometric techniques


Zaafarany(2012)

13. Na alginate Mixed corrosioninhibition system(but anodicallycontrolled)

AZ31 alloygrade/3.5 wt% NaCl

Polarization, EIS, SEMcoupled EDS and FTIRspectroscopy

Authors attributedcorrosion inhibition tomolecular adsorption andsubsequent formation ofcompact film (freshlygenerated magnesiumhydroxide) on the metalsurface

Dang et al.(2015)

14. Alginate cationic surfactant Mixed corrosioninhibition system(but cathodicallycontrolled)

Carbon steel/1 MHCl

Gravimetric,electrochemical, EDXand SEM techniques


Tawfik (2015)

15. Ca aginate gel loaded withimidazoline quaternaryammonium salts

– P110 steel/CO2-saturated 3.5 wt%NaCl

UV–visspectrophotometry,SEM and EIStechniques

The improved protection inthe presence of thiscomposite was attributedto the automatic release ofimidazoline corrosioninhibitors at themetal/solution interface.BaSO4 was alsoencapsulated withalginate/imidazolinecomposite in order to aidsinking and corrosionretardation was well

Wang et al.(2015)

16. Hydroxyl propyl alginate Mixed typeinhibitor system

Mild steel/1 M HCl Weight loss,electrochemical(Polarization and EIS)



at&tfs

3w

mitUiscyclaEotuRBB

dsorption was also explained in terms of adsorption isotherm,hermodynamic and kinetic parameters (Sangeetha, Meenakshi,

Sundaram, 2016a, 2016b). Typical examples of inhibition sys-ems involving dextrin, alginates and their derivatives deployedor metal corrosion reduction in various aggressive media are pre-ented in Table 4.

. Effect of halide ion additives on corrosion inhibitionith carbohydrate polymers

In many aggressive media, depending of the service environ-ent to which an organic inhibitor is being deployed, corrosion

nhibition is normally aimed at achieving the maximum reduc-ion in metal dissolution with the utmost efficiency (Eduok, Inam,moren, & Akpan, 2013; Eduok & Khaled, 2014, 2015). With this

n mind, the improvement of the performance of any inhibitionystem employed becomes a very importance aspect of the wholeorrosion reduction program. Researchers worldwide over theears have developed a number of additives to synergistically aidorrosion reduction in the presence of organic compounds regard-ess of their modes of action and surface chemistries; most of thesedditives are halides (Eduok, Umoren, & Udoh, 2012; Umoren,duok, & Oguzie, 2008c). The application of some halides withrganic inhibitors have been widely reported as having greaterotal inhibition effect compared to when only one of inhibitors
sed independently; hence synergism (Caliskan & Bilgic, 2000;idhwan, Rahim, & Shah, 2012; Tang, Li, Mu, Li, & Liu, 2006;ouklah, Hammouti, Aouniti, Benkaddour, & Bouyanzer, 2006;entiss, Bouanis, Mernari, Traisnel, & Lagrenee, 2002). This unique
techniques, AFM, SEMand FTIR

property of halides has been largely linked with the formation ofion-pairs between the organic inhibitors and the halide ions lead-ing to increased surface coverage. Since molecular adsorption isa key factor in corrosion inhibition, the ionic radii as well as theelectronegativity of these ions have been conceived to contributeimmensely to corrosion inhibition. Synergistic effect of halide ionshave been found to follow this order depending on their ionicradii (pm): I− (206) > Br− (182) > Cl− (167). Iodides, in particular,have been known for improved inhibition due to their hydropho-bicity and the stabilization of adsorbed ions with the cations ofmost organic polymers leading to increased metal surface cover-age (Bouklah et al., 2006). The initial adsorption of iodide ionson the surface of metal substrate aids further molecular adsorp-tion of organic inhibitor by coulombic attraction thereby formingmore stable protective film at the metal/solution interface (Musa,Mohamad, Kadhum, Takriff, & Tien, 2011; Harek & Larabi, 2004).Since most organic inhibitors are thermally unstable, their usage incombination with halides becomes necessary, prompting enhancedmetal surface protection from aggressive ions and molecules atincreased temperature. Umoren and Solomon (2015) have recentlyreported a comprehensive review on the some inhibitor–halidesystems for metal inhibition, yet studies involving the effects ofhalide ions on the corrosion inhibition of biopolymers are scarce,although there have been more investigations (Umoren et al., 2010;Rajeswari et al., 2013; Arukalam et al., 2015) on substituted cellu-lose compounds than any other class of carbohydrate biopolymer in
the literature. Table 5 lists carbohydrate ploymer-halide inhibitionsystems deployed for metal corrosion studies in various aggressivemedia including the reasons for corrosion inhibition in the presenceof the halide ions.


Table 5Bioploymer-halide inhibition systems deployed for metal corrosion studies in various aggressive media.

S/N Inhibitor system (halidetype)

Type of metalsubstrate/corrosive media


Reason for corrosion inhibitionin the presence of the halide(Halide effect)

References

1. Gum Arabic incombination withpotassium iodide

Aluminium/0.1 M NaOH Weight loss and hydrogenevolution techniques

Synergism (with KI) Umoren (2009)

2. Carboxymethyl cellulosein combination withpotassium halides (withKCl, KBr, KI)

Mild steel (AISI 1005grade)/2 M H2SO4.


Inhibitor molecular adsorptionon the metal surface; Halideions demonstrated bothantagonism (Cl− and Br− ions)and synergism towards theinhibition potency ofCarboxymethyl cellulose

Umoren et al. (2010)

3. Hydroxypropyl cellulose[Authors also studiedglucose and gellan gum] incombination with KI

Cast iron/1 M HCl Weight loss andpotentiodynamic polarizationtechniques, electrochemicalimpedance spectroscopy

KI demonstrated bothantagonism and synergismtowards the inhibition potencyof Hydroxypropyl cellulose

Rajeswari et al. (2013)

4. Hydroxyethyl cellulosein combination (with KI)

Mild steel/0.5 M H2SO4. Weight loss andpotentiodynamic polarizationtechniques; electrochemicalimpedance spectroscopy.Quantum chemical calculationsusing the density functionaltheory (DFT) was employed todetermine the relationshipbetween molecular structureand inhibition efficiency

Potassium iodide enhanced theinhibition performance of thesystem by bridging the chargedsteel substrate and the organicinhibitor (synergism)

Arukalam et al. (2015)

5. Hydroxypropylmethylcellulose (with KI)

Aluminium (AA 1060type)/0.5 M H2SO4.

Weight loss andpotentiodynamic polarizationtechniques, electrochemicalimpedance spectroscopy.Quantum chemicalcalculations (by DFT) was alsoused to correlate the corrosioninhibition with the molecularstructure of Hydroxypropylmethylcellulose

Synergism (with KI) Arukalam et al. (2014a)

6. Hydroxyethyl Cellulose(with KI)

Aluminium (AA 1060 type)and Mild Steel/0.5 MH2SO4.

Same as Arukalam et al.(2014a)

Synergism (with KI) Arukalam et al. (2014b)

7. Hydroxypropylmethylcellulose (with KI)

Mild steel/0.5 M H2SO4. Same as Arukalam et al.(2014a)

Synergism (with KI) Arukalam (2014)

8. Ethyl HydroxyethylCellulose (with KI)

Mild steel/1 M H2SO4. Same as Arukalam et al.(2014a)

Synergism (with KI) Arukalam et al. (2014c)

9. Gum Arabic (with KCl,KBr, KI)

Aluminium/0.1 M NaOH Hydrogen evolution andthermometric techniques

Synergism (with KBr and KI);Antagonism (with KCl)

Umoren et al. (2006a, 2006b)

10. Raphia hookeri exudategum (with KCl, KBr, KI)

Aluminium/0.1 M HCl. Weight loss, hydrogenevolution and thermometrictechniques


Umoren and Ebenso (2009)

olutioic met

o2gteaiaapimrawaoh

11. Exudate gum extractedfrom Pachylobus edulis(with KCl, KBr, KI)

Mild steel/2 M H2SO4. Hydrogen evthermometr

The effect of halide ions (Cl−, Br−, and I−) additives at 30–60 ◦Cn the inhibition performance of CMC on mild steel corrosion in

M H2SO4 has been investigated using weight loss and hydro-en evolution techniques (Umoren et al., 2010). In the presence ofhe halide additives, corrosion inhibition was found to be depend-nt on their concentrations as well as the solution temperaturend immersion period. Mild steel corrosion inhibition for CMCncreased greatly in the presence of the iodide ions, and this wasttributed to a synergistic effect while the presence of chloride ionsntagonized the proposed inhibition process, with and without therincipal inhibitor (CMC), from the results of both corrosion mon-

toring techniques. The weight loss technique at 30 ◦C revealedagnitudes of corrosion inhibition efficiency (%�) of 89 and 65%,

espectively, in the presence and absence of 5 mM I−, while 48nd 63% were recorded for 5 mM Cl− and Br−. Corrosion inhibition
as linked with metal surface adsorption of inhibitor compounds
nd this followed Langmuir adsorption isotherm in the presencef the halide ions. Conversely, corrosion performance for eachalide ion deceased with temperature due to molecular desorption

n andhods


Umoren and Ekanem (2010)

at higher solution temperatures. In another study, authors havereported the enhance inhibition performance of hydroxypropylmethylcellulose and hydroxyethyl cellulose (substituted cellulosiccompounds; SCC) in 0.5 M H2SO4 for aluminium (AA 1060 type) andmild steel using weight loss and electrochemical polarization andimpedance spectroscopy (Arukalam, Madufor, Ogbobe, & Oguzie,2014a; Arukalam, Madu, Ijomah, Ewulonu, & Onyeagoro, 2014b;Arukalam, 2014). The formation of passive oxide film on the Alsurface was found to dissolve in the acidic test solution, but therate of dissolution decreased on addition of SCC. Improved pro-tection for SCC was recorded in the presence of 500 mg/L KI asEIS revealed increased corrosion resistance in the presence of thishalide ion. Adsorption of SCC in the presence of the iodide ionson Al followed Freundlich (Arukalam et al., 2014a, 2014b) andLangmuir (Arukalam, 2014) adsorption isotherm models. Hydrox-
ypropyl methylcellulose-KI was revealed as a mixed-type inhibitor(though dominantly cathodic) from Tafel results. Authors furtherexplained the relationship between hydroxypropyl methylcellu-lose adsorption and corrosion mechanism using DFT approach

hydrat

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o quantum chemical calculations. Another corrosion inhibitionerformance of a biopolymer (ethyl hydroxyethyl cellulose; EHC)ttributed to synergistic effect of iodide ion addition has beeneported for mild steel in 1 M H2SO4 using experimental (chemicalnd electrochemical) and theoretical (quantum chemical calcula-ions by DFT) evaluations (Arukalam, Madufor, Ogbobe, & Oguzie,014c). Corrosion resistance was found to increase in the presencef 0.5 g/L KI added to the test solution with %� values up 58 and 52%ecorded in the presence and absence of KI. Polarization resultsevealed that both EHC and EHC–KI were mixed-type inhibitorystems though predominantly cathodic while their adsorptionollowed Langmuir isotherm. Experimental evaluations were pre-eded by theoretical molecular orbitals and reactivity assessmentsf EHC’s structure in other to correlate its adsorption to the mech-nism of inhibition using DFT. The effect of halide ions on thenhibition performances of exudate gums extracted from floralources have also been investigated for some metal substratesn different media. In alkaline and acidic media, the effective-ess of Gum Arabic (GA) towards the corrosion inhibition of Alas also been studied in the presence of these halide additivesetween 30 and 60 ◦C, using hydrogen evolution and thermomet-ic techniques (Umoren, 2009; Umoren et al., 2006a, 2006b). Theorrosion inhibition of GA of Al in 0.1 M NaOH and H2SO4 wasnhanced in the presence of the iodide ions due to synergistic effect,nd values of %� of GA-KI systems increased with temperatureith corrosion inhibition attributed to adsorption (obeying Temkin

dsorption isotherm in NaOH and Langmuir, Temkin and Freund-ich in H2SO4). Corrosion performance of GA was greatly reduced inhe presence of chloride ions, demonstrating antagonist effect forl substrate in both corrodents. Al corrosion inhibition followed

he order I− > Br− > Cl−. Umoren and Ebenso (2009) have inves-igated the Al corrosion inhibition with exudate gum extractedrom Raphia hookeri and the effects of KCl, KBr and KI additionn its potency in 0.1 M HCl. Authors employed weight loss, hydro-en evolution and thermometric techniques in their evaluation forll the systems studied between 30 and 60 ◦C. From the resultsf the findings, it was revealed that the inhibition performancef this gum extract was found to increase synergistically with KInd KBr in the solution of the acid electrolyte while KCl disallowedhe adsorption of the gum unto the metal surface, thereby reduc-ng its corrosion efficiency. Raphia hookeri exudates gum inhibition

as attributed to molecular adsorption of its chemical constituentsnd this was collaborated with Freundlich, Langmuir and Temkindsorption isotherms. Similar study have been reported for a Pachy-obus edulis gum-KI system in 2 M H2SO4 using hydrogen evolutionnd thermometric methods investigated between 30 and 60 ◦C forild steel corrosion (Umoren & Ekanem, 2010). Corrosion rate of

he mild steel substrate reduced in the presence of the gum extractut more with the extract in combination with KI. Corrosion inhi-ition for both gum and gum-KI systems reduced with immersionime and with solution temperature. Physical adsorption was pro-osed from the dependence of temperature with trend of corrosion

nhibition in the presence of the inhibitors studied; and adsorptionas approximated with Temkin adsorption isotherm.

. Future perspective: Computational approach toorrosion inhibition evaluation

In some cases where core experimental results are inconclu-ive, computational approach to corrosion inhibition is necessary.xperimental evaluations should always be supported with
heoretical-based assessments of inhibition phenomena; espe-ially the use of molecular modelling tools in correlating corrosionnhibition mechanisms with molecular structures of the inhibitorompounds (Obot et al., 2009; Obot, Ebenso, & Kabanda, 2013; Obot
e Polymers 140 (2016) 314–341 337

& Obi-Egbedi, 2010; Ebenso et al., 2012; Kabanda et al., 2012).Quantum chemical modelling has been widely used in studyingmolecular orbitals and reactivity of organic inhibitors in other tofully understand their adsorption on metal surfaces in any aggres-sive (ionic) medium (Obot & Obi-Egbedi, 2010; Ebenso et al., 2012;Kabanda et al., 2012; Obot et al., 2013; Obot, Macdonald, & Gasem,2015; Kayaa, Tüzüna, Kaya, & Obot, 2015; Sasikumar et al., 2015;Obot, 2014). Since the mechanism of corrosion inhibition is notfully understood, model-based theoretical computations allow foran attempt to elucidate the possible phases of inhibition reactionsin complex systems, hence, solving some obscured surface adhe-sion problems by mechanistic predictions of applicable parameters.Carbohydrates from gum exudate show reliable reduction towardscorrosion of metal substrates deployed in acidic and alkaline media,yet, it is difficult to assign inhibition to one chemical specie amongstthe lot abound in these extracts. Bio-gums alone are mixtures ofpolysaccharides and/or glycoproteins, with typical arabinose andribose sources. However, the use to molecular dynamics simu-lation (MDS) could serve as a very effective tool is studying theadsorption of principal chemical constituents on the surfaces ofmetals, and also further explain the inhibitor–metal surface inter-action, giving multiple views on possible molecular motions inthe microscopic level (Obot et al., 2015; Kayaa et al., 2015; Obot,2014). The principle of classical MDS could also help in comput-ing time-dependent properties of this complex molecular systemsas well as giving practical information about most stable confor-mations of inhibitor constituents prior to adsorption. Aspects ofMDS could also include the study of the complexities and dynamicsof inhibition processes involving polysaccharide polymeric sys-tems by relating their inhibition mechanisms with conformationalchanges and surface stability (Obot et al., 2015; Kayaa et al., 2015;Sasikumar et al., 2015; Obot, 2014). Other aspects of molecu-lar structure contributing to corrosion inhibition are the energygap and the energies associated with frontier orbitals. By usingDensity Functional Theory (DFT), energies of the highest occu-pied molecular orbital (HOMO) and lowest unoccupied molecularorbital (LUMO) have been widely collaborated with corrosion inhi-bition in terms of molecular adsorption sites on surfaces (Obot& Obi-Egbedi, 2010; Ebenso et al., 2012; Kabanda et al., 2012;Obot et al., 2009, 2013). The use of MDS and quantum chemicalcomputational tools is therefore necessary for future studies ofadsorption processes involving corrosion inhibition with carbohy-drate biopolymers. Only few reports are available in the literaturewith regards to the application of quantum chemical computations(El-Haddad, 2013, 2014; Arukalam et al., 2014a, 2015; Umorenet al., 2015a, 2015b; Alsabagh, Elsabee, Moustafa, Elfky, & Morsi,2014).

5. Concluding remarks

Temperature and solution pH are some of the few factors affect-ing the rate of metal dissolution in any service environment towhich they are deployed; and this can be hugely reduced if effi-cient control procedure is employed to revert the overall corrosiondynamics. The use of biopolymers is gaining grounds in the fabri-cation of inhibitor formulations for various field applications, andtheir chemistry is simple since the adsorption mechanism accom-panying them involves either physical adsorption at metal surfaces,or by chemisorption. Some mixtures of carbohydrate polymers arealso known to contain chemical constituents capable of formingpassivation layers that prevent the passage of corrosive ions and
molecule across the metal/solution interface.
Carbohydrate biopolymers, as used in this review, are macro-compounds that possess monomeric units covalently bondedto form long macromolecular sugar chains with relatively high

3 hydrat

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olecular masses. They are readily available in nature, benign,enewable and ecofriendly alternative to other organic inhibitorsith toxic potentials. In corrosion inhibition, they represent a set of

hemically stable, biodegradable and ecofriendly macromoleculesith reliable inhibiting strengths for metal surface protection;aking them effective protective coatings and metal linings. This

eview work has elaborately described the inhibition of metalorrosion using some green pure polysaccharide biopolymers asell as their mixtures (including modifications and nanocom-osites) found in the literature. Exudate gums, cellulose, starch,ectin and pectates, chitosans and carrageenan, alginate and dex-rin have been reviewed including the effects of halide additives onheir anticorrosion performances. Molecular weights and molecu-ar structures/symmetry and functional group chemistry are fewharacteristics of these compounds that have been also describedo affect the mechanisms of their protection in aqueous media.he mechanism of molecular adsorption in the presence of halideon leads to increased metal surface coverage, and this has beenxplained with typical examples based on formation of ion-pairs.orrosion inhibition with polymer-halide conjugates have alsoeen described in terms of coulombic attraction between polymersnd halide ions at the metal/solution interface, thereby formingore stable protective film. Corrosion process designs are best

nderstood if at the molecular level, the important factors con-eived to affect the behaviour of the system are addressed. Suchpproach is better explained using computational/theoretical tools.part from fostering further understanding of corrosion processes,

he theoretical correlating of inhibition mechanisms with molecu-ar structures of the carbohydrate polymeric compounds will alsoid the studying of molecular orbitals and reactivity of inhibitors as

key to understanding adsorption on surfaces. Molecular dynamicimulations also allow for the studying of stable conformationsrior to adsorption as well as the time-dependent properties ofhis complex molecular systems.

cknowledgments

The authors gratefully acknowledged Centre of Research Excel-ence in Corrosion, Research Institute, KFUPM and King Fahdniversity of Petroleum and Minerals (KFUPM) for supporting theork.

eferences

bdallah, M. (2004). Guar gum as corrosion inhibitor for carbon steel in sulfuricacid solutions. Portugaliae Electrochimica Acta, 22, 161–175.

bu-Dalo, M. A., Othman, A. A., & Al-Rawashdeh, N. A. F. (2012). Exudate gum fromacacia trees as green corrosion inhibitor for mild steel in acidic media.International Journal of Electrochemical Science, 7, 9303–9324.

ghzzaf, A. A., Rhouta, B., Steinmetz, J., Rocca, E., Aranda, L., Khalil, A., et al. (2012).Corrosion inhibitors based on chitosan-heptanoate modified beidellite. AppliedClay Science, 65–66, 173–178.

hmed, R. A., Farghali, R. A., & Fekry, A. M. (2012). Study for the stability andcorrosion inhibition of electrophoretic deposited chitosan on mild steel alloy inacidic medium. International Journal of Electrochemical Science, 7, 7270–7282.

l-Bonayan, A. M. (2014). Sodium aliginate as corrosion inhibitor for carbon steelin 0.5 M HCl solutions. International Journal of Scientific & Engineering Research,5(4), 611–618.

lsabagh, A. M., Elsabee, M. Z., Moustafa, Y. M., Elfky, A., & Morsi, R. E. (2014).Corrosion inhibition efficiency of some hydrophobically modified chitosansurfactants in relation to their surface active properties. Egyptian Journal ofPetroleum, 23, 349–359.

meh, P. O., & Eddy, N. O. (2014). Characterization of Acacia Sieberiana (AS) gumand their corrosion inhibition potentials for zinc in sulphuric acid medium.international journal of novel research in physics. Chemistry & Mathematics,1(1), 25–36.

meh, P. O., Magaji, L., & Salihu, T. (2012). Corrosion inhibition and adsorptionbehaviour for mild steel by Ficus glumosa gum in H2SO4 solution. African
Journal of Pure and Applied Chemistry, 6, 100–106.
ntony, N., Sherine, H. B., & Rajendran, S. (2010). Investigation of the inhibitingeffect of carboxymethylcellulose-Zn2+ system on the corrosion of carbon steelin neutral chloride solution. Arabian Journal for Science and Engineering, 35,42–52.

e Polymers 140 (2016) 314–341

Arthur, D. E., Jonathan, A., Ameh, P. O., & Anya, C. (2013). A review on theassessment of polymeric materials used as corrosion inhibitor of metals andalloys. International Journal of Industrial Chemistry, 4, 2–9.

Arukalam, I. O. (2012). The inhibitive effect of hydroxyethylcellulose on mild steelcorrosion in hydrochloric acid solution. Academic Research International, 2,35–42.

Arukalam, I. O. (2014). Durability and synergistic effects of KI on the acid corrosioninhibition of mild steel by hydroxypropyl methylcellulose. CarbohydratePolymers, 112, 291–299.

Arukalam, I. O., Madufor, I. C., Ogbobe, O., & Oguzie, E. (2014). Experimental andtheoretical studies of hydroxyethyl cellulose as inhibitor for acid corrosioninhibition of mild steel and aluminium. The Open Corrosion Journal, 6, 1–10.

Arukalam, I. O., Madu, I. O., Ijomah, N. T., Ewulonu, C. M., & Onyeagoro, G. N. (2014).Acid corrosion inhibition and adsorption behaviour of ethyl hydroxyethylcellulose on mild steel corrosion. Journal of Materials,doi.org/10.1155/2014/101709

Arukalam, I. O., Madufor, I. C., Ogbobe, O., & Oguzie, E. E. (2014c). Hydroxypropylmethylcellulose as a polymeric corrosion inhibitor for aluminium. Pigment &Resin Technology, 43, 151–158.

Arukalam, I. O., Madufor, I. C., Ogbobe, O., & Oguzie, E. E. (2014d). Acidic corrosioninhibition of copper by hydroxyethyl cellulose. British Journal of Applied Science& Technology, 4, 1445–1460.

Arukalam, I. O., Madufor, C., Ogbobe, O., & Oguzie, E. E. (2015). Inhibition of mildsteel corrosion in sulfuric acid medium by hydroxyethyl cellulose. ChemicalEngineering Communications, 202, 112–122.

Atta, A. M., El-Mahdy, G. A., Al-Lohedan, H. A., & Ezzat, A. R. O. (2015). Synthesis ofnonionic amphiphilic chitosan nanoparticles for active corrosion protection ofsteel. Journal of Molecular Liquids, 211, 315–323.

Aziz, M. A., Cabral, J. D., Brooks, H. J. L., Moratti, S. C., & Hanto, L. R. (2012).Antimicrobial properties of a chitosan dextran-based hydrogel for surgical use.Antimicrobial Agents and Chemotherapy, 56(1), 280–287.

Bayol, E., Gürten, A. A., Dursun, M., & Kayakirilmaz, K. (2008). Adsorption behaviorand inhibition corrosion effect of sodium carboxymethyl cellulose on mildsteel in acidic medium. Acta Physico-Chimica Sinica, 24, 2236–2243.

Banerjee, S., Srivastava, V., & Singh, M. M. (2012). Chemically modified naturalpolysaccharide as green corrosion inhibitor for mild steel in acidic medium.Corrosion Science, 59, 35–41.

Behpour, M., Ghoreishi, S. M., Khayatkashani, M., & Soltani, N. (2011). The effect oftwo oleo-gum resin exudate from Ferula assa-foetida and Dorema ammoniacumon mild steel corrosion in acidic media. Corrosion Science, 53, 2489–2501.

Bello, M., Ocho, N., Balsamo, V., López-Carrasquero, F., Coll, S., Monsalve, A., et al.(2010). Modified cassava starches as corrosion inhibitors of carbon steel: Anelectrochemical and morphological approach. Carbohydrate Polymers, 82,561–568.

Bentiss, F., Bouanis, M., Mernari, B., Traisnel, M., & Lagrenee, M. (2002). Effect ofiodide ions on corrosion inhibition of mild steel by3,5-bis(4-methylthiophenyl)-4H-1,2,4-triazole in sulfuric acid solution. Journalof Applied Electrochemistry, 32, 671–678.

Bentrah, H., Rahali, Y., & Chala, A. (2014). Gum Arabic as an eco-friendly inhibitorfor API 5L X42 pipeline steel in HCl medium. Corrosion Science, 82,426–431.

Biswas, A., Pal, S., & Udayabhanu, G. (2015). Experimental and theoretical studiesof xanthan gum and its graft co-polymer as corrosion inhibitor for mild steel in15% HCl. Applied Surface Science, 353, 173–183.

Bouklah, M., Hammouti, B., Aouniti, A., Benkaddour, M., & Bouyanzer, A. (2006).Synergistic effect of iodide ions on the corrosion inhibition of steel in 0.5 MH2SO4 by new chalcone derivatives. Applied Surface Science, 252, 6236–6242.

Brindha, T., Mallika, J., & Sathyanarayana, M. V. (2015). Synergistic effect betweenstarch and substituted piperidin-4-one on the corrosion inhibition of mild steelin acidic medium. Journal of Materials and Environmental Science, 6, 191–200.

Brown, W. H., & Poon, T. (2005). Introduction to organic chemistry (3rd ed.).Hoboken, New Jersy, USA: Wiley., ISBN 0-471-44451-0.

Busch, V. M., Kolender, A. A., Santagapita, P. R., & Buera, M. P. (2015). Vinal gum, agalactomannan from Prosopis ruscifolia seeds: Physicochemicalcharacterization. Food Hydrocolloids, 51, 495–502.

Caliskan, N., & Bilgic, S. (2000). Effect of iodide ions on the synergistic inhibition ofthe corrosion of manganese-14 steel in acidic media. Applied Surface Science,153, 128–133.

Carneiro, J., Tedimb, J., Fernandesa, S. C. M., Freire, C. S. R., Silvestre, A. J. D.,Gandinia, A., et al. (2012). Chitosan-based self-healing protective coatingsdoped with cerium nitrate for corrosion protection of aluminum alloy 2024.Progress in Organic Coatings, 75, 8–13.

Carneiro, J., Tedim, J., Fernandes, S. C. M., Freire, C. S. R., Gandini, A., Ferreira, M. G.S., et al. (2013a). Chitosan as a smart coating for controlled release of corrosioninhibitor 2-mercaptobenzothiazole. ECS Electrochemical Letters, 2(6),2162–8726.

Carneiro, J., Tedim, J., Fernandes, S. C. M., Freire, C. S. R., Gandini, A., Ferreira, M. G.S., et al. (2013b). Functionalized chitosan-based coatings for active corrosionprotection. Surface & Coatings Technology, 226, 51–59.

Chaires-Martínez, L., Salazar-Montoya, J. A., & Ramos-Ramírez, E. G. (2008).Physicochemical and functional characterization of the galactomannan
obtained from mesquite seeds (Prosopis pallida). European Food Research andTechnology, 227, 1669–1676.
Chauhan, K., Kumar, R., Kumar, M., Sharma, P., & Chauhan, G. S. (2012). Modifiedpectin-based polymers as green antiscalants for calcium sulfate scaleinhibition. Desalination, 30, 31–37.

http://refhub.elsevier.com/S0144-8617(15)01216-3/sbref0005


































































































































































































































































































































































































































































































































































































































































































































































































































































































hydrat

C

C

D

D

D

D

E

E

E

E

E

E

E

E

E

E

E

E

F

F

F

F

F

F

G

G


heng, S., Chen, S., Liu, T., Chang, X., & Yin, Y. (2007). Carboxymethyl chitosan–Cu2+

mixture as an inhibitor used for mild steel in 1.0 M HCl. Electrochimica Acta, 52,5932–5938.

hung, Y. C., Yeh, J. Y., & Tsai, C. F. (2011). Antibacterial characteristics and activityof water-soluble chitosan derivatives prepared by the maillard reaction.Molecules, 16, 8504–8514.

ang, N., Wei, Y. H., Hou, L. F., Li, Y. G., & Guo, C. L. (2015). Investigation of theinhibition effect of the environmentally friendly inhibitor sodium alginate onmagnesium alloy in sodium chloride solution. Materials and Corrosion, 66,1354–1362.

esai, M. N., & Desai, S. M. (1970). Inhibition of the corrosion of A1-3S in NaOH.Corrosion Science, 10, 233–237.

eyab, M. A. (2015). Hydroxyethyl cellulose as efficient organic inhibitor ofzinc-carbon battery corrosion in ammonium chloride solution:Electrochemical and surface morphology studies. Journal of Power Sources, 280,190–194.

ouiare, M., & Norton, I. T. (2013). Designer colloids in structured food for thefuture (short survey). Journal of the Science of Food and Agriculture, 93,3147–3154.

benso, E. E., Kabanda, M. M., Arslan, T., Saracoglu, M., Kandemirli, F., Murulana, L.C., et al. (2012). Quantum chemical investigations on quinoline derivatives aseffective corrosion inhibitors for mild steel in acidic medium. InternationalJournal of Electrochemical Science, 7, 5643–5676.

ddy, N. O., Ibok, U. J., & Ebenso, E. E. (2010). Adsorption, synergistic inhibitiveeffect and quantum chemical studies on ampicillin and halides for thecorrosion of mild steel. Journal of Applied Electrochemistry, 40, 445–456.

ddy, N. O., Odiongenyi, A. O., Ameh, P. O., & Ebenso, E. E. (2012). Corrosioninhibition potential of Daniella Oliverri gum exudate for mild steel in acidicmedium. International Journal of Electrochemical Science, 7, 7425–7439.

ddy, N. O., Ameh, P. O., & Odiongenyi, A. O. (2014). Physicochemicalcharacterization and corrosion inhibition potential of Ficus benjamina (FB) gumfor aluminum in 0.1 M H2SO4. Portugaliae Electrochimica Acta, 32(3), 183–197.

duok, U. M., Umoren, S. A., & Udoh, A. P. (2012). Synergistic inhibition effectsbetween leaves and stem extracts of Sida acuta and iodide ion for mild steelcorrosion in 1 M H2SO4 solutions. Arabian Journal of Chemistry, 5, 325–337.

duok, U., Inam, E., Umoren, S. A., & Akpan, I. A. (2013). Chemical andspectrophotometric studies of naphthol dye as an inhibitor for aluminiumalloy corrosion in binary alkaline medium. Geosystem Engineering, 16,146–155.

duok, U. M., & Khaled, M. M. (2014). Corrosion protection of non-alloyed AIAI316L concrete steel metal grade in aqueous H2SO4: Electroanalytical andsurface analyses with Metiamide. Construction and Building Materials, 68,285–290.

duok, U. M., & Khaled, M. (2015). Corrosion inhibition for low-carbon steel in 1 MH2SO4 solution by phenytoin: Evaluation of the inhibition potency of another“anticorrosive drug”. Research on Chemical Intermediates, 41, 6309–6324.

id, S., Abdallah, M., Kamar, E. M., & El-Etre, A. Y. (2015). Corrosion inhibition ofaluminum and aluminum silicon alloys in sodium hydroxide solutions bymethyl cellulose. Journal of Materials and Environmental Science, 6, 892–901.

l-Haddad, M. N. (2013). Chitosan as a green inhibitor for copper corrosion inacidic medium. International Journal of Biological Macromolecules, 55, 142–149.

l-Haddad, M. N. (2014). Hydroxyethyl cellulose used as an eco-friendly inhibitorfor 1018 c-steel corrosion in 3.5% NaCl solution. Carbohydrate Polymers, 112,595–602.

l-Sawy, S. M., Abu-Ayana, Y. M., & Abdel-Mohdy, F. A. (2001). Somechitin/chitosan derivatives for corrosion protection and waste watertreatments. Anti-Corrosion Methods and Materials, 48(4), 227–234.

an, B., Wei, G., Zhang, Z., & Qiao, N. (2014). Preparation of supramolecularcorrosion inhibitor based on hydroxypropyl-bcyclodextrin/octadecylamineand its anti-corrosion properties in the simulated condensate water.Anti-Corrosion Methods and Materials, 61, 104–111.

ares, M. M., Maayta, A. K., & Al-Mustafa, J. A. (2012). Corrosion inhibition ofiota-carrageenan natural polymer on aluminum in presence of zwitterionmediator in HCl media. Corrosion Science, 65, 223–230.

ares, M. M., Maayta, A. K., & Al-Qudah, M. M. (2012). Pectin as promising greencorrosion inhibitor of aluminum in hydrochloric acid solution. CorrosionScience, 60, 112–117.

ekry, A. M., & Mohamed, R. R. (2010). Acetyl thiourea chitosan as an eco-friendlyinhibitor for mild steel in sulphuric acid medium. Electrochimica Acta, 55,1933–1939.

eng, Y., Lin, X., Li, H., He, L., Sridhar, T., Suresh, A. K., et al. (2014). Synthesis andcharacterization of chitosan-grafted BPPO ultrafiltration compositemembranes with enhanced antifouling and antibacterial properties. IndustrialEngineering Chemistry and Research, 53, 14974–14981.

iori-Bimbi, M. V., Alvarez, P. E., Vaca, H., & Gervasi, C. A. (2015). Corrosioninhibition of mild steel in HCL solution by pectin. Corrosion Science, 92,192–199.

abriel, J. S., Tiera, M. J., & Tiera, V. A. O. (2015). Synthesis, characterization, andantifungal activities of amphiphilic derivatives of diethylaminoethyl chitosanagainst Aspergillus flavus. Journal of Agricultural and Food Chemistry, 63,5725–5731.

eethanjali, R., Ali, A., Sabirneeza, F., & Subhashini, S. (2014). Water-soluble andbiodegradable pectin-grafted polyacrylamide and pectin-grafted polyacrylicacid: Electrochemical investigation of corrosion-inhibition behaviour on mildsteel in 3.5% NaCl media. Indian Journal of Materials Science, 2014,doi.org/10.1155/2014/356075.

e Polymers 140 (2016) 314–341 339

Gräfen, H., Horn, E. M., Schlecker, H., & Schindler, H. (2002). Ullmann’sencyclopedia of industrial chemistry. In Corrosion. Weinheim: Wiley-VCH.http://dx.doi.org/10.1002/14356007.b01 08

Grassino, A., Halambek, J., Djakovic, S., Brncic, S. R., Dent, M., & Grabaric, Z. (2016).Utilization of tomato peel waste from canning factory as a potential source forpectin production and application as tin corrosion inhibitor. FoodHydrocolloids, 52, 265–274.

Harek, Y., & Larabi, L. (2004). Corrosion inhibition of mild steel in 1 mol/dm3 HCl byoxalic N-phenylhydrazide N0-phenylthiosemicarbazide. Chemistry in Industry,53, 55–61.

Hassan, R. M., Fawzy, A., Ahmed, G. A., Zaafarany, I. A., Asghar, B. H., Takagi, H. D.,et al. (2011). Kinetics and mechanism of permanganate oxidation of iota- andlambda-carrageenan polysaccharides as sulfated carbohydrates in acidperchlorate solutions. Carbohydrate Research, 346, 2260–2267.

Hassan, R., Zaafarany, I., Gobouri, A., & Takagi, H. (2013). A revisit to the corrosioninhibition of aluminum in aqueous alkaline solutions by water-solublealginates and pectates as anionic polyelectrolyte inhibitors. InternationalJournal of Corrosion,. Doi.org/10.1155/2013/508596.

Hassan, R. M., & Zaafarany, I. A. (2013). Kinetics of corrosion inhibition ofaluminum in acidic media by water-soluble natural polymeric pectates asanionic polyelectrolyte inhibitors. Materials, 6, 2436–2451.

Hromádková, Z., Malovikova, A., Mozes, S., Sroková, I. E., & Ibringerová, A. (2008).Hydrophobically modified pectates as novel functional polymers in food andnon-food applications. BioResources, 3, 71–78.

Hussein, M. H. M., El-Hady, M. F., Shehata, H. A. H., Hegazy, M. A., & Hefni, H. H. H.(2013). Preparation of some eco-friendly corrosion inhibitors havingantibacterial activity from sea food waste. Journal of Surfactants and Detergents,16, 233–242.

Jayalakshmi M, & Muralidharan, V. S. (1997). Inhibitors for aluminium corrosion inaqueous medium. Corrosion Reviews, 15(3–4), 315–340.

John, S., Joseph, A., Jose, A. J., & Narayana, B. (2015). Enhancement of corrosionprotection of mild steel by chitosan/ZnO nanoparticle composite membranes.Progress in Organic Coatings, 84, 28–34.

Kabanda, M. M., Murulana, L. C., Ozcan, M., Karadag, F., Dehri, I., Obot, I. B., et al.(2012). Quantum chemical studies on the corrosion inhibition of mild steel bysome triazoles and benzimidazole derivatives in acidic medium. InternationalJournal of Electrochemical Science, 7, 5035–5056.

Kalaivania, R., Arasub, P. T., & Rajendran, S. (2013). Inhibitive nature ofcarboxymethylcellulose with Zn2+ ion. Chemical Science Transactions, 2,1352–1357.

Kayaa, S., Tüzüna, B., Kaya, C., & Obot, I. B. (2015). Determination of corrosioninhibition effects of amino acids: Quantum chemical and molecular dynamicsimulation study. Journal of the Taiwan Institute of Chemical Engineers,doi.org/10.1016/j.jtice.2015.06.009.

Keppler, F., Hamilton, J. T. G., Bra, M., & Röckmann, T. (2006). Methane emissionsfrom terrestrial plants under aerobic conditions. Nature, 439,187–191.

Khairou, K. S., & El-Sayed, A. (2003). Inhibition effect of some polymers on thecorrosion of cadmium in a hydrochloric acid solution. Journal of AppliedPolymer Science, 88, 866–871.

Killaars, J., & Finley, P. (2001). SPE international symposium on oilfield chemistry.In SPE 65044.

Kim, S. R. B., Choi, Y. G., Kim, J. Y., & Lim, S. T. (2015). Improvement of watersolubility and humidity stability of tapioca starch film by incorporating variousgums. LWT-Food Science and Technology, doi.org/10.1016/j.lwt.2015.05.009.

Klinov, I. Y. (1962). New polymeric materials in anticorrosion technology. In Trudy.Vsesoyuznoy Mezhvuzovskoy Nauchnoy Konferentsii po Voprosam Bor’by sKorroziyey. pp. 296–303. Moskva: Gostoptekhizdat.

Li, M. L., Li, R. H., Xu, J., Han, X., Yao, T. Y., & Wang, J. (2014).Thiocarbohydrazide-modified chitosan as anticorrosion and metal ionadsorbent. Journal of Applied Polymer Science, http://dx.doi.org/10.1002/APP.40671

Li, M., Xu, J., Li, R., Wang, D., Li, T., Yuan, M., et al. (2014). Simple preparation ofaminothiourea-modified chitosan as corrosion inhibitor and heavy metal ionadsorbent. Journal of Colloid and Interface Science, 417, 131–136.

Li, R., & Feke, D. L. (2015). Rheological and kinetic study of the ultrasonicdegradation of locust bean gum in aqueous saline and salt-free solutions.Ultrasonics Sonochemistry, 27, 334–338.

Li, X., & Deng, S. (2015). Cassava starch graft copolymer as an eco-friendlycorrosion inhibitor for steel in H2SO4 solution. Korean Journal of ChemicalEngineering, 32, 1–8.

Li, H., Li, H., Liu, Y., & Huang, X. (2015). Synthesis of polyamine grafted chitosancopolymer and evaluation of its corrosion inhibition performance. Journal ofthe Korean Chemical Society, 59, 142–147.

Liu, Y., Zou, C., Yan, X., Xiao, R., Wang, T., & Li, M. (2015). �-Cyclodextrin modifiednatural chitosan as a green inhibitor for carbon steel in acid solutions.Industrial Engineering Chemistry and Research, 54, 5664–5672.

Liu, Y., Zou, C., Li, C., Lin, L., & Chen, W. (2016). Evaluation of�-cyclodextrin–polyethylene glycol as green scale inhibitors forproduced-water in shale gas well. Desalination, 377, 28–33.

Loto, C. A., & Loto, R. T. (2013). Effect of dextrin and thiourea additives on the zinc
electroplated mild steel in acid chloride solution. International Journal ofElectrochemical Science, 8, 12434–12450.
Luckachan, G. E., & Mittal, V. (2015). Anti-corrosion behavior of layer by layercoatings of cross-linked chitosan and poly(vinyl butyral) on carbon steel.Cellulose, 22, 3275–3290.




























































































































































































































































































































































































































































































































































































































































































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animaran, M., Rajendran, S., Manivannan, M., Thangakani, J. A., & Prabha, A. S.(2013). Corrosion inhibition by carboxymethyl cellulose. European ChemicalBulletin, 2, 494–498.

ishra, R. K., Sutar, P. B., Singhal, J. P., & Banthia, A. K. (2007). Graftcopolymerization of pectin with polyacrylamide. Polymer-Plastics Technologyand Engineering, 46, 1079–1085.

obin, M., Khan, M. A., & Parveen, M. (2011). Inhibition of mild steel corrosion inacidic medium using starch and surfactants additives. Journal of AppliedPolymer Science, 121, 1558–1565.

ohamed, R. R., & Fekry, A. M. (2011). Antimicrobial and anticorrosive activity ofadsorbents based on chitosan Schiff’s base. International Journal ofElectrochemical Science, 6, 2488–2508.

usa, A. Y., Mohamad, A. B., Kadhum, A. A. H., Takriff, M. S., & Tien, L. T. (2011).Synergistic effect of potassium iodide with pthalazone on the corrosioninhibition of mild steel in 1.0 M HCl. Corrosion Science, 53, 3672–3677.

ada, C., Katarina, B., & Sandra, P. (1996). The inhibition effect of pectin andascorbic acid on the corrosion of tin in sodium chloride solution. In 47th annualmeeting of the international society of electrochemistry. Abstracts/TheInternational Society of Electrochemistry (ed).—The Electrochemical Society,1996. L6a-3. 47th annual meeting of the international society ofelectrochemistry, Veszprem-Balatonfured, Hungary, 1.-6.09. 1996.

anaki, S. G., Kyzas, G. Z., Tzeremec, A., Papageorgiou, M., Kostoglou, M., Bikiaris, D.N., et al. (2015). Synthesis and characterization of modified carrageenanmicroparticles for the removal of pharmaceuticals from aqueous solutions.Colloids and Surfaces B: Biointerfaces, 127, 256–265.

bot, I. B., Obi-Egbedi, N. O., & Umoren, S. A. (2009). Antifungal drugs as corrosioninhibitors for aluminium in 0.1 M HCl. Corrosion Science, 51, 1868–1875.

bot, I. B., & Obi-Egbedi, N. O. (2010). Adsorption properties and inhibition of mildsteel corrosion in sulphuric acid solution by ketoconazole: Experimental andtheoretical investigation. Corrosion Science, 52, 198–204.

bot, I. B., Ebenso, E. E., & Kabanda, M. M. (2013). Metronidazole asenvironmentally safe corrosion inhibitor for mild steel in 0.5 M HCl:Experimental and theoretical investigation. Journal of Environmental ChemicalEngineering, 1, 431–439.

bot, I. B. (2014). Recent advances in computational design of organic materials forcorrosion protection of steel in aqueous media. In Developments in corrosionprotection. pp. 123–151. Croatia: INTECH.

bot, I. B., Macdonald, D. D., & Gasem, Z. M. (2015). Density functional theory (DFT)as a powerful tool for designing new organic corrosion inhibitors. Part 1: Anoverview. Corrosion Science, 99, 1–30.

kafor, P. C., Ikpi, M. E., Uwah, I. E., Ebenso, E. E., Ekpe, U. J., & Umoren, S. A. (2008).Inhibitory action of Phyllanthus amarus extracts on the corrosion of mild steelin acidic media. Corrosion Science, 50, 2310–2317.

atel, P. R., Pandya, J. M., & Keemtilal. (1981). Colloids as corrosion inhibitors foraluminium copper alloy in hydrochloric acid. Proceedings of Indian NationalScience Academy, 47, 555–561.

eter, A., Obot, I. B., & Sharma, S. K. (2015). Use of natural gums as green corrosioninhibitors: An overview. International Journal of Industrial Chemistry, 6,153–164.

rabakaran, M., Ramesh, S., Periasamy, V., & Sreedhar, B. (2015). The corrosioninhibition performance of pectin with propyl phosphonic acid and Zn2+ forcorrosion control of carbon steel in aqueous solution. Research on ChemicalIntermediates, 41, 4649–4671.

u, D. (2006). Behavior of dinonylphenol phosphate ester and its influence on theoxidation of a Zn anode in alkaline solution. Journal of Power Sources, 162,706–712.

abea, E. I., Badawy, M. E. T., Stevens, C. V., Smagghe, G., & Steurbaut, W. (2003).Chitosan as antimicrobial agent: Applications and mode of action.Biomacromolecules, 4, 1457–1465.

ahim, A. A., Rocca, E., Steinmetz, E. J., & Kassim, M. J. (2008). Inhibitive action ofmangrove tannins and phosphoric acid on pre-rusted steel via electrochemicalmethods. Corrosion Science, 50, 1546–1550.

aja, P. B., Fadaeinasab, M., Qureshi, A. K., Rahim, A. A., Osman, H., Litaudon, M.,et al. (2013). Evaluation of green corrosion inhibition by alkaloid extracts ofOchrosia oppositifolia and Isoreserpiline against mild steel in 1 M HCl medium.Industrial & Engineering Chemistry Research, 52, 10582–10593.

ajendran, S., Joany, R. M., Apparao, B. V., & Palaniswamy, N. (2002). Corrosioninhibition by carboxymethyl cellulose-1-hydroxyethane-1, 1-diphosphonicacid-Zn2+ system. Bulletin of Electrochemistry, 18, 25–28.

ajendran, S., Sridevi, S. P., Anthony, N., John, A. A., & Sundearavadivelu, M. (2005).Corrosion behaviour of carbon steel in polyvinyl alcohol. Anti-CorrosiveMethods and Materials, 52, 102–107.

ajeswari, V., Kesavan, D., Gopiramanb, M., & Viswanathamurthi, P. (2013).Physicochemical studies of glucose, gellan gum, and hydroxypropylcellulose—Inhibition of cast iron corrosion. Carbohydrate Polymers, 95,288–294.

idhwan, A. M., Rahim, A. A., & Shah, A. M. (2012). Synergistic effect of halide ionson the corrosion inhibition of mild steel in hydrochloric acid using mangrovetannin. International Journal of Electrochemical Science, 7, 8091–8104.

osliza, R., & Nik, W. B. W. (2010). Improvement of corrosion resistance of AA6061alloy by tapioca starch in seawater. Current Applied Physics, 10,
221–229.
oy, P., Karfa, P., Adhikari, U., & Sukul, D. (2014). Corrosion inhibition of mild steelin acidic medium by polyacrylamide grafted Guar gum with various graftingpercentage: Effect of intramolecular synergism. Corrosion Science, 88,246–253.

e Polymers 140 (2016) 314–341

Saidia, N., Elmsellema, H., Ramdania, M., Chetouania, A., Azzaouib, K., Yousfia, F.,et al. (2015). Using pectin extract as eco-friendly inhibitor for steel corrosion in1 M HCl media. Der PharmaChemica, 7(5), 87–94.

Sakai, T., Sakamoto, T., Hallaert, J., & Vandamme, E. J. (1993). Pectin, pectinase, andprotopectinase: Production, properties, and applications. Advances in AppliedMicrobiology, 39, 213–294.

Sangeetha, Y., Meenakshi, S., & Sundaram, C. S. (2015). Corrosion mitigation ofN-(2-hydroxy-3-trimethyl ammonium)propyl chitosan chloride as inhibitor onmild steel. International Journal of Biological Macromolecules, 72,1244–1249.

Sangeetha, Y., Meenakshi, S., & Sundaram, C. (2016). Interactions at the mild steelacid solution interface in the presence of O-fumaryl-chitosan: Electrochemicaland surface studies. Carbohydrate Polymers, 136, 38–45.

Sangeetha, Y., Meenakshi, S., & Sundaram, C. S. (2016). Investigation of corrosioninhibitory effect of hydroxyl propyl alginate on mild steel in acidic media.Journal of Applied Polymer Science, http://dx.doi.org/10.1002/APP.43004

Sasikumar, Y., Adekunle, A. S., Olasunkanmi, L. O., Bahadur, I., Baskar, R., Kabanda,M. M., et al. (2015). Experimental, quantum chemical and Monte Carlosimulation studies on the corrosion inhibition of some alkyl imidazolium ionicliquids containing tetrafluoroborate anion on mild steel in acidic medium.Journal of Molecular Liquids, 211, 105–118.

Schweiger, R. G. (1962). Acetyl pectates and their reactivity with polyvalent metalions. Journal of Organic Chemistry, 27, 1789.

Shibad, P. R., & Balachandra, J. (1976). Behaviour of titanium and its alloy withhydrofluoric acid in HCI and H2SO4 solutions with addition agents.Anti-Corrosion Methods and Materials, 23, 16–28.

Smith, A. M. (2001). The biosynthesis of starch granules. Biomacromolecules, 2(2),335–341.

Solomon, M. M., Umoren, S. A., Udosoro, I. I., & Udoh, A. P. (2010). Inhibitive andadsorption behaviour of carboxymethyl cellulose on mild steel corrosion insulphuric acid solution. Corrosion Science, 52, 1317–1325.

Sriram, J. G., Sadhir, M. H., Saranya, M., & Srinivasan, A. (2014). Novel corrosioninhibitors based on seaweeds for AA7075 aircraft aluminium alloys. ChemicalScience Review and Letters, 2, 402–407.

Sugama, T. (1997). Oxidized potato-starch films as primer coatings of aluminium.Journal of Materials Science, 3, 3995–4003.

Sugama, T., & DuVall, J. E. (1996). Polyorganosiloxane-grafted potato starchcoatings for protecting aluminum from corrosion. Thin Solid Films, 289, 39–48.

Suyanto, H. D. K., Ratih, R., & Leo, S. A. (2015). Application chitosan derivatives asinhibitor corrosion on steel with fluidization method. Journal of Chemical andPharmaceutical Research, 7, 260–267.

Talati, J. D., & Modi, R. M. (1976). Colloids as corrosion inhibitors foraluminium–copper alloy in sodium hydroxide. Anti-Corrosion Methods andMaterials, 23, 6–9.

Tang, L., Li, X., Mu, G., Li, L., & Liu, G. (2006). Synergistic effect between4-(2-pyridylazo) resorcin and chloride ion on the corrosion of cold rolled steelin 0.5 M sulfuric acid. Applied Surface Science, 252, 6394–6401.

Tawfik, S. M. (2015). Alginate surfactant derivatives as ecofriendly corrosioninhibitor for carbon steel in acidic environment. RSC Advances, http://dx.doi.org/10.1039/C5RA20340F

Umoren, S. A., Obot, I. B., Ebenso, E. E., Okafor, P. C., Ogbobe, O., & Oguzie, E. E.(2006). Gum arabic as a potential corrosion inhibitor for aluminium in alkalinemedium and its adsorption characteristics. Anti-Corrosion Methods andMaterials, 53, 277–282.

Umoren, S. A., Ogbobe, O., & Ebenso, E. E. (2006). Synergistic inhibition ofaluminium corrosion in acidic medium by gum arabic and halide ions.Transactions of the SAEST (Society for Advancement of Electrochemical Science andTechnology), 41, 74–81.

Umoren, S. A. (2008). Inhibition of aluminium and mild steel corrosion in acidicmedium using Gum Arabic. Cellulose, 15, 751–761.

Umoren, S. A., Ogbobe, O., Igwe, I. O., & Ebenso, E. E. (2008). Inhibition of mild steelcorrosion in acidic medium using synthetic and naturally occurring polymersand synergistic halide additives. Corrosion Science, 50, 1998–2006.

Umoren, S. A., Obot, I. B., Ebenso, E. E., & Obi-Egbedi, N. (2008). Studies on theinhibitive effect of exudate gum from Dacroydes edulis on the acid corrosion ofaluminium. Portugaliae Electrochimica Acta, 26, 199–209.

Umoren, S. A., Eduok, U. M., & Oguzie, E. E. (2008). Corrosion inhibition of mildsteel in 1 M H2SO4 by polyvinyl pyrrolidone and synergistic iodide additives.Portugaliae Electrochimica Acta, 26, 533–546.

Umoren, S. A. (2009). Synergistic Influence of gum arabic and iodide ion on thecorrosion inhibition of aluminium in alkaline medium. PortugaliaeElectrochimica Acta, 27, 565–577.

Umoren, S. A., Obot, I. B., & Obi-Egbedi, N. O. (2009). Raphia hookeri gum as apotential eco-friendly inhibitor for mild steel in sulfuric acid. Journal ofMaterials Science, 44, 274–279.

Umoren, S. A., Obot, I. B., Ebenso, E. E., & Obi-Egbedi, N. O. (2009). The Inhibition ofaluminium corrosion in hydrochloric acid solution by exudate gum fromRaphia hookeri. Desalination, 247, 561–572.

Umoren, S. A., & Ebenso, E. E. (2009). Studies of the anti-corrosive effect of Raphiahookeri exudate gum-halide mixtures for aluminium corrosion in acidicmedium. Pigment Resin Technology, 37, 173–182.

Umoren, S. A., & Ekanem, U. F. (2010). Inhibition of mild steel corrosion in H2SO4

using exudate gum from Pachylobus edulis and synergistic potassium halideadditives. Chemical Engineering Communications, 197, 1339–1356.

Umoren, S. A., Solomon, M. M., Udosoro, I. I., & Udoh, A. P. (2010). Synergistic andantagonistic effects between halide ions and carboxymethyl cellulose for the






























































































































































































































































































































































































































































































































































































































































































































































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corrosion inhibition of mild steel in sulphuric acid solution. Cellulose, 17,635–648.

moren, S. A., Eduok, U. M., Solomon, M. M., & Udoh, A. P. (2011). Corrosioninhibition by leaves and stem extracts of Sida acuta for mild steel in 1 M H2SO4

solutions investigated by chemical and spectroscopic techniques. ArabianJournal of Chemistry, http://dx.doi.org/10.1016/j.arabjc.2011.03.008

moren, S. A., Banera, M. J., Garcia, T. A., Gervasi, C. A., & Mirıfico, M. V. (2013).Inhibition of mild steel corrosion in HCl solution using chitosan. Cellulose, 20,2529–2545.

moren, S. A., Eduok, U. M., & Solomon, M. M. (2014). Effect ofpolyvinylpyrrolidone–polyethylene glycol blends on the corrosion inhibitionof aluminium in HCl solution. Pigment & Resin Technology, 43, 299–313.

moren, S. A., & Solomon, M. M. (2015). Effect of halide ions on the corrosioninhibition efficiency of different organic species–A review. Journal of Industrialand Engineering Chemistry, 21, 81–100.

moren, S., Solomon, M. M., Israel, A. U., Eduok, U. M., & Jonah, A. E. (2015).Comparative study of the corrosion inhibition efficacy of polypropylene glycoland poly (methacrylic acid) for mild steel in acid solution. Journal of DispersionScience and Technology, 36, 1721–1735.

moren, S. A., Obot, I. B., Madhankumar, A., & Gasem, Z. M. (2015). Performanceevaluation of pectin as ecofriendly corrosion inhibitor for X60 pipeline steel inacid medium: Experimental and theoretical approaches. CarbohydratePolymers, 124, 280–291.

an de Velde, F., & DeRuiter, G. A. (2005). Carrageenan: Polysaccharides. In
Biopolymers online. Wiley-VCH Verlag GmbH & Co. KGaA. http://dx.doi.org/10.1002/3527600035.bpol6009
athsala, K., Venkatesha, T. V., Praveen, B. M., & Nayana, K. O. (2010).Electrochemical generation of Zn–chitosan composite coating on mild steeland its corrosion studies. Engineering, 2, 580–584.

e Polymers 140 (2016) 314–341 341

Verbeken, D., Diercka, S., & Dewttinck, K. (2003). Exudate gums: Occurrence,production and applications (A review). Applied Microbiology & Biotechnology,10, 1354–1457.

Wang, L., Zhang, C., Xie, H., Sun, W., Chen, X., Wang, X., et al. (2015). Calciumalginate gel capsules loaded with inhibitor for corrosion protection ofdownhole tube in oilfields. Corrosion Science, 90, 296–304.

Yan, X., Zou, C., & Qin, Y. (2014). A new sight of water-soluble polyacrylamidemodified by �-cyclodextrin as corrosion inhibitor for X70 steel. Starch/Stärke,66, 968–975.

Zaafarany, I. (2006). Inhibition of acidic corrosion of iron by some carrageenancompounds. Current World Environment, 1(2), 101–108.

Zaafarany, I. (2012). Corrosion Inhibition of aluminum in aqueous alkalinesolutions by alginate and pectate water-soluble natural polymer anionicpolyelectrolytes. Portugaliae Electrochimica Acta, 30,419–426.

Zaafarany, I. A., Khairou, K. S., & Hassan, R. M. (2009). Acid-catalysis of chromic acidoxidation of kappa-carrageenan polysaccharide in aqueous perchloratesolutions. Journal of Molecular Catalysis A: Chemical, 302, 112–118.

Zheludkevich, M. L., Tedim, J., Freire, C. S. R., Fernandes, S. C. M., Kallip, S., Lisenkov,A., et al. (2011). Self-healing protective coatings with “green” chitosan basedpre-layer reservoir of corrosion inhibitor. Journal of Materials Chemistry, 21,4805–4812.

Zou, C., Yan, X., Qin, Y., Wang, M., & Liu, Y. (2014). Inhibiting evaluation ofb-cyclodextrin-modified acrylamide polymer on alloy steel in sulfuric solution.
Corrosion Science, 85, 445–454.
Zou, C., Liu, Y., Yan, X., Qin, Y., Wang, M., & Zhou, L. (2014). Synthesis of bridged�-cyclodextrinepolyethylene glycol and evaluation of its inhibitionperformance in oilfield wastewater. Materials Chemistry and Physics, 147,521–527.

















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