research article inhibitive action of ferrous gluconate on aluminum alloy...

Hindawi Publishing CorporationAdvances in Materials Science and EngineeringVolume 2013 Article ID 639071 8 pageshttpdxdoiorg1011552013639071

Research ArticleInhibitive Action of Ferrous Gluconate on Aluminum Alloyin Saline Environment

Patricia Abimbola Idowu Popoola1 Sanni Omotayo1

Cleophas A Loto12 and Olawale Muhammed Popoola3

1 Department of Chemical Metallurgical and Materials Engineering Tshwane University of Technology PMB X680Pretoria 0001 South Africa

2 College of Science and Technology Covenant University Ota Ogun State Nigeria3 Department of Electrical Engineering Tshwane University of Technology PMB X680 Pretoria 0001 South Africa

Correspondence should be addressed to Patricia Abimbola Idowu Popoola popoolaapitutacza

Received 26 June 2013 Revised 14 October 2013 Accepted 1 November 2013

Academic Editor Martin Crimp

Copyright copy 2013 Patricia Abimbola Idowu Popoola et al This is an open access article distributed under the Creative CommonsAttribution License which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

The corrosion of aluminum in saline environment in the presence of ferrous gluconate was studied using weight loss and linearpolarization methods The corrosion rates were studied in different concentrations of ferrous gluconate 05 10 15 and 20 gmLat 28∘C Experimental results revealed that ferrous gluconate in saline environment reduced the corrosion rate of aluminum alloyat the different concentrations studied The minimum inhibition efficiency was obtained at 15 gmL concentration of inhibitorwhile the optimum inhibition efficiency was achieved with 10 gmL inhibitor concentration The results showed that adsorptionof ferrous gluconate on the aluminium alloy surface fits Langmuir adsorption isotherm The potentiodynamic polarization resultsshowed that ferrous gluconate is a mixed type inhibitor Ferrous gluconate acted as an effective inhibitor for aluminium alloy withinthe temperature and concentration range studied The data obtained from weight loss and potentiodynamic polarization methodswere in good agreement

1 Introduction

Aluminum and its alloys are known to be used in industriesdue to their weight-to-strength ratios good resistance tocorrosion excellent workability and high electrical con-ductivity [1ndash4] In spite of these attractive properties ofaluminum in the presence of aggressive ions like chloridethe protective layer can be locally destroyed and corrosiveattack takes place [5 6] Corrosion control and preventionare unavoidablemajor scientific issues thatmust be addresseddaily as far as there are increasing applications of metallicmaterials in all facets of technological development [7]The main corrosion issue with aluminum and its alloys isthe localized breakdown of the passive film which leadsto the initiation and growth of corrosion pits in chloridemedium [8ndash10] Corrosion can be prevented by appropriatemodifications of the environment which in turn suppress

retard or completely stop the cathodic or anodic reactionsor both This can be achieved by the use of inhibitors [11ndash13] Corrosion inhibitors are substances which when addedin small concentrations to corrosive environments decreaseor prevent the reaction of themetal with themedia Inhibitorsare added to many systems such as refinery units coolingsystems pipelines oil and gas production units [14] Due tothe various economic importance and industrial applicationsof aluminum and its alloys its protection against corrosionhas attracted much attention [15ndash22] The authors [23] stud-ied the corrosion inhibition of aluminum alloy in 2M HCland HNO

3with Arachis hypogaea natural oil as an inhibitor

using potentiodynamic polarization and gravimetric tech-niques at 25∘C The obtained results showed that Arachishypogaea oil in 2MHCl and HNO

3

minus solutions decreased thecorrosion rate of aluminum alloy at different concentrationsof inhibitor considered the scanning electron microscope

2 Advances in Materials Science and Engineering

Table 1 Chemical composition of aluminium alloy (wt)

Si Fe Cu Mn Mg Cr Ti Ca Zr V Al0157 0282 00025 0024 051 0023 0006 00011 0002 00035 Balance

surface morphology of as-corroded uninhibited conditionshowed severe pits and damage formation than those of as-corroded inhibited conditions The authors concluded thatadditions of Arachis hypogaea as corrosion inhibitor foraluminumalloy indicate a high inhibition efficiency potentialvalue and polarization resistance with decrease in currentdensity The authors of [24] studied the interfacial behaviorof fluconazole (FLC) as a corrosion inhibitor for aluminumin hydrochloric acid solution between hydrochloric acidand aluminum using weight loss method The experimen-tal results revealed that fluconazole exhibits an excellentcorrosion inhibitor property for aluminum in hydrochloricacidic medium The authors of [25] worked on the effect ofsolution pH on the anticorrosion performance of differentinhibitors K

2Cr2O7 CeCl

3 and Ce(dbp)

3on aluminum

alloy (AA2024-T3) using themultielectrode and conventionalpotentiodynamic polarization methods The results showedthat the K

2Cr2O7at 10minus4M after 30min of exposure time

behaves as the best inhibitor across the studied pH rangeThe authors of [26] worked on the influence of bromideand iodide ions on the inhibitive effect of polyacrylamide(PA) on aluminum corrosion in HCl solution using weightloss hydrogen evolution and thermometric techniques at30 and 60∘C The experimental results show that the halideadditives synergistically increased the inhibition efficiency ofpolyacrylamide and the increase in inhibition efficiency wasfound to be more obvious in iodide than bromide ions

Gluconic acid occurs naturally in honey fruit kom-bucha tea and wine [27] They are environmentally suitablenontoxic compounds and gluconates are part of the suc-cessful commercial corrosion inhibitors Gluconic acid andits derivatives are used as ingredients in various hygienicproducts for scale removal in metal cleanings as householdcleaning compounds including mouth washer metal finish-ing and for water treatment operation Sodium calciumand zinc salts of gluconic acid have been reported to beeffective nontoxic inhibitors for tin iron and mild steel innear neutral solution [27ndash29] The efficiency of gluconateinhibition depends on pH value inhibitor concentrationchemical composition of investigated solution the nature ofcations introduced in the solution as gluconate and the stateof the metal surface [30] Different mechanisms of corrosioninhibition by gluconate were proposed It is speculated thatgluconate can repair the oxide film by its adsorption on theexposed metal surface in weak spots of porous oxide filmGluconates can be incorporated in the oxide film during itsformation andor gluconate are forming more or less solublecomplexes that can be precipitated on the metal surface [30]In view of this it is essential to study the corrosion behaviorof aluminum in ferrous gluconate solutionThe present studyaimed at evaluating the potential of ferrous gluconate as aninhibitor for aluminum alloy in saline medium using weightloss and potentiodynamic polarization methods

HO

HO

HO

HO

HO

O

O Ominus

Ominus

OH

OH

OH

OH

OH

Fe+2

Figure 1 Molecular structure of ferrous gluconate

2 Experimental

21 Materials and Sample Preparation Aluminum alloy withthe chemical composition presented in Table 1 was usedas substrate material for weight loss and potentiodynamicpolarization studies The aluminum alloy plate was cut usinga Struers cutting machine with a Discotom-5 cut-off wheelA Struers lubricant which works as a coolant was usedduring cutting The substrate was cut and machined todimensions 12 times 12 times 12mm The aggressive solution ofsodium chloride purchased from SMM Instruments (Pty)Ltd South Africa was used for this study The chemicalstructure of ferrous gluconate is shown in Figure 1 purchasedfrom SMM Instruments (Pty) Ltd South Africa An insulatedcopper wire was connected to one side of the sample usingan aluminum conducting tape and cold mounted in methylmethacrylate resin leaving one surface of an area of 1 cm2for potentiodynamic polarization measurement the exposedsurface area was abraded with different grates of emerypapers degreased with acetone rinsed in distilled waterdried weighed and stored in a desiccator The initial weightof the samples was taken and recorded In each experiment005M NaCl solution was prepared freshly as requiredCorrosion studies were carried out at 28∘C

22 Weight Loss Measurement The weight loss test wasconducted on the aluminum alloy weighed samples in theabsence and presence of different concentrations of inhibitorat 28∘C Volume of the solution used was 200mL and theconcentration of the inhibitor was in the range of 05 1015 and 20 gmL in saline environment The samples werewashed with distilled water dried in acetone and weighedat an interval of 48 hours of immersion time Corrosion

Advances in Materials Science and Engineering 3

Table 2 Electrochemical polarization parameters for aluminium alloy in 005M NaCl solution in the absence and presence of ferrousgluconate at 28∘C

Concentration ofinhibitor(gmL)

Current density(Acm2)

Anodic Tafelconstant(Vdec)

Cathodic Tafelconstant(Vdec)

Linearpolarization(Ωcm2)

Corrosionpotential

(V)

Corrosion rate(mmyr)

00 859119864 minus 06 005087 008004 157119864 + 03 minus075893 02778705 721119864 minus 07 017081 039458 718119864 + 04 minus105640 00233410 496119864 minus 09 074904 150350 438119864 + 07 minus034318 00001615 476119864 minus 07 052492 054034 243119864 + 05 minus057367 00055420 649119864 minus 09 192670 096634 430119864 + 07 minus034318 000021

rate degree of surface coverage and inhibitor efficiencywere determined for each inhibitor concentration using thefollowing equations

Corrosion rate (mmyr) =

876119882

119863119860119879

(1)

where119882 is weight loss (mg)119863 is specimen density (gcm3)119860 is specimen area (cm2) and 119879 is exposure time (hour)

Degree of surface coverage (120579) = CR∘ minus CRCR∘

Percentage inhibition efficiency (IE)

= (CR∘ minus CRCR∘) times 100

(2)

where CR and CR∘ are the corrosion rates of the specimensin the presence and absence of inhibitor respectively

23 Potentiodynamic Polarization Measurements Potentio-dynamic polarization tests were carried out using threeelectrode glass cells with an AUTOLAB Potentiostat (modelReference-668) which was connected to a personal com-puter to control the experiments A graphite rod satu-rated AgAgCl and aluminum alloy specimen were usedas counter reference and working electrode respectivelyThe polarization experiments data were analyzed by NOVAsoftware version 18The polarization curves were carried outwith minus15 V cathodic potential and +15 V anodic potentialat a scan rate of 00016Vsec From the linear Tafel plot ofthe cathodic and anodic curves corrosion rate corrosionpotential (119864corr) and corrosion current densities (119894corr) wereobtained

24 Scanning Electron Microscopy (SEM) Analysis The scan-ning electronmicroscope images of the aluminum alloy sam-ples were recorded via JEOL JSM-7600F scanning electronmicroscope

3 Results and Discussion

The variations in corrosion rate and percentage inhibitionefficiency (IE) with immersion time at different concen-trations of ferrous gluconate for 28 days of exposure are

0

005

01

015

02

025

03

2 4 6 8 10 12 14 16 18 20 22 24 26 28

Cor

rosio

n ra

te (m

my

r)

Exposure time (days)

Control

minus005

05 FG1 FG

15 FG2 FG

Figure 2 Variation of corrosion rate with exposure time foraluminum alloy specimen immersed in 005M NaCl solution withferrous gluconate addition

shown in Figures 2 and 3 Table 2 shows the numerical valuesof the corrosion current density (119894corr) corrosion potential(119864corr) linear polarization resistance (LPR) corrosion rateand anodic and cathodic Tafel slopes (120573

119886and 120573

119888) with

different concentrations of ferrous gluconate Figure 4 showsthe potentiodynamic polarization curves for aluminum alloydissolution in saline solution in the absence and presence ofdifferent concentrations of ferrous gluconate at 28∘C Figure 5shows the SEM micrograph while Figure 6 illustrates theLangmuir adsorption isotherm In Figure 7 a comparativechart of the inhibition efficiency obtained from weight lossand potentiodynamic polarization methods was presented

31 Corrosion Rate and Inhibitor Efficiency From the resultsthe corrosion rate of the aluminum alloy in saline environ-ment decreased in the presence of all the different concen-trations of inhibitor studied Figure 2 shows that aluminumalloy in 005M NaCl solution with 10 gmL concentrationof inhibitor showed an excellent corrosion resistance Inthe presence of 05 gmL concentration of ferrous gluconatethe corrosion rate value was 0051mmyr after 28 days ofexposure time compared to the absence of ferrous glu-conate which gave 0110mmyr after 28 days of exposure


0

20

40

60

80

100

120

2 4 6 8 10 12 14 16 18 20 22 24 26 28

Inhi

bitio

n effi

cien

cy (

)


05 FG1 FG

15 FG2 FG

Figure 3 Variation of inhibition efficiency with exposure time foraluminum alloy specimen immersed in 005M NaCl solution withferrous gluconate addition

time This shows 54 reduction in corrosion rate valuecompared to the absence of inhibitor This revealed thatferrous gluconate inhibits the corrosion of aluminum alloy insalinemediumThe results showed that percentage inhibitionefficiency (IE) of ferrous gluconate depends on the inhibitorconcentrations The results also indicated that the optimuminhibitor efficiency of ferrous gluconate was obtained at aconcentration of 10 gmL with 100 percentage efficiencyIt is generally assumed that the adsorption of inhibitor atmetalsolution interface is the first step in the mechanism ofinhibition in aggressive media [29] It was observed that atinhibitor concentration greater than 10 gmL the corrosionrate was slightly increased This could be attributed to excessaddition of inhibitor to the saline medium and that certainconcentration of ferrous gluconate will have a detrimentaleffect on corrosion rate

Therefore the adsorption of ferrous gluconate onto thesurface of the aluminum alloy at all concentration stud-ied prevents the breakdown of the film leading to highercorrosion resistance of the aluminum alloy The inhibitioneffect of ferrous gluconate decreases graduallywith increasingconcentration values which implies that ferrous gluconatehas a beneficial effect even at low concentrations Thissuggests the formation of soluble ferrous gluconate complex[29 31 32]

32 Potentiodynamic Polarization Measurements Resultsobtained show that the cathodic and anodic curves demon-strated a Tafel type behaviour The presence of ferrousgluconate significantly changes both anodic and cathodicregion when compared to the absence of inhibitor [33]Thuscathodic and anodic reactions were interfered in the presenceof ferrous gluconate which implies that the ferrous gluconateshowed an effective inhibitory effect on cathodic hydrogenreduction reaction and anodic dissolution of aluminum alloyAlso the result implies that ferrous gluconate acts as a mixed

Pote

ntia

l (V

)

Control

minus2

minus15

minus1

minus05

0

05

1

15

2

100E minus 11 100E minus 09 100E minus 07 100E minus 05 100E minus 03 100E minus 01

05FG10FG

15FG20FG

Current density (Acm2)

Figure 4 Linear polarization of aluminum alloy in 005M NaClsolutionferrous gluconate environment at 28∘C

type inhibitor This can be explained on the basis of specificadsorption of ferrous gluconate anions and on the basis of thecompetitive adsorption between the ferrous gluconate anionsand Clminus ions on the electrode surface and therefore retard theClminus destructive action [34] Apparently the bond between thesurface atoms of the metal and the adsorbed inhibitor anionsis strong which can inhibit oxidation [34] The corrosionpotential (119864corr) values shifted to the less negative values inthe presence of inhibitor From Table 2 it is clear that thecorrosion current value decreased from 859E-06Acm2 to496E-09Acm2 in the presence of 10 gmL concentration offerrous gluconate in 005M NaCl solution 119887

119886and 119887119888values

changed significantly and 119864corr shifted to cathodic regionhence ferrous gluconate acted as mixed type inhibitor

The polarization resistance value of aluminum increasesfrom 16E03 cm2 in the absence of inhibitor to 438E07 cm2in the presence of 10 gmL concentration of inhibitorand the corrosion rate value decreases from 027787 to0000162mmyr in the presence of 10 gmL (ses Figure 8)The decrease in corrosion rate and corrosion current density(119894corr) in the presence of all the different concentrations offerrous gluconate studied proved that ferrous gluconate act asan effective corrosion inhibitor for aluminum alloy in salineenvironment at 28∘C

Anodic and cathodic processes of aluminum corrosion insaline medium are dissolution of aluminum and reduction ofdissolved oxygen respectively as [35]

4Al 997888rarr 4Al3+ + 12eminus (3)

3O2+ 6H2O + 12eminus 997888rarr 12OHminus (4)


Electron image 1100120583m

Spectrum 3

(a)


Spectrum 5

(b)

Figure 5 SEMmicrograph of the aluminum alloy sample (a) in 005M NaCl solution (b) with ferrous gluconate after 28 days of immersion

0

05

1

15

2

25

05 1 15 2

y = 05x

R2 = 1

C120579

C (gmL)

Figure 6 Langmuir adsorption isotherm of ferrous gluconate onthe aluminum surface in 005MNaCl solution obtained fromweightloss method at 28∘C

Therefore Al3+ reacts with OHminus to form aluminum hydrox-ide near the aluminum surface as follows

4Al + 3O2+ 6H2O 997888rarr 4Al(OH)

3 (5)

33 Scanning Electron Microscopy (SEM) The surface mor-phology of the aluminum alloy surface in saline environmentin the absence and presence of ferrous gluconate after 28days of immersion in sodium chloride medium is shown inFigure 5The surface seen in Figure 5(a) is due to the chlorideions attack on the aluminum alloy sample Flakes showingcorrosion products like metal hydroxides and its oxides canbe observed [13] The corrosion process in deep seawateroccurs under very specific conditions and is characterizedmainly by high chloride contents and the presence of CO

2

microorganisms and H2S [36] Figure 5(b) shows the SEM

micrograph of the specimen after 28 days of immersion insodium chloride with the presence of ferrous gluconate Itwas observed that the corrosion products on the surface ofthe aluminum in sodium chloride with ferrous gluconatecondition are minimal when compared with the micrographin the absence of inhibitor (Figure 5(a)) The surface of thespecimen was noticed to be enclosed with a thin layer of the

0

20

40

60

80

100

05 1 15 2

IE (

)

LPRWLM

C (gmL)

PP-icorrPP-CR

Figure 7 Comparative chart of inhibitor efficiency (IE) of alu-minum alloy in 005M NaCl solution in the presence of differentconcentrations of ferrous gluconate obtained from weight loss andpotentiodynamic polarization methods

ferrous gluconate molecules which protects the metal againstcorrosion [35]

34 Adsorption Behavior Figure 6 shows the Langmuiradsorption isotherms of ferrous gluconate on the aluminumalloy corrosion in 005M NaCl solution The linearity in theresult at various concentrations of ferrous gluconate provesthat the inhibition effect of the inhibitor was as a result of theadsorption of ferrous gluconate on the surface of the metalThe degree of surface coverage (120579) obtained from weight losstest varied linearly with the inhibitor concentration which fitfor Langmuir adsorption isotherm [37] Since the correctionfactors (1198772) is unity (1) the adsorption behaviour of theinhibitor is assumed to have obeyed Langmuir adsorptionisotherms

35 Inhibitor Efficiency The percentage inhibition efficiency(IE) of aluminum alloy in saline environment in the


80

85

90

95

100

105

05 1 15 2

IE (

)

C (gmL)

y = minus16075x2 + 1034x + 83573

R2 = 07873

PP-CR

PP-CRPoly ( )PP-CR

(a)

80

82

84

86

88

90

92

94

96

98

100

102

05 1 15 2

y = minus07175x2 + 55325x + 88033

R2 = 04065

C (gmL)

IE (

)

PP-icorr

Poly ( )PP-icorr

PP-icorr

(b)

965

97

975

98

985

99

995

100

1005

05 1 15 2

LPR

LPRPoly (LPR)

y = minus0385x2 + 2515x + 95885

R2 = 07352

C (gmL)

IE (

)

(c)

Figure 8 Relationship between concentration and corrosion rate (CR) current density (119894corr) and linear polarization (LPR)

presence of different concentrations of ferrous gluconatewas obtained using equation reported elsewhere [15 17]from weight loss and potentiodynamic polarization tech-niques The values of IE () from the weight loss linearpolarization resistance (LPR) potentiodynamic polarization-corrosion rate (PP-CR) and potentiodynamic polarization-current density (PP-119894corr) measurements obtained by usingfollowing equations

IE PP-119894corr () = 100 times119894corr minus 119894

∘

corr119894corr (6)

IE PP-CR () = 100 times CR minus CR∘

CR (7)

IE PP-LPR () = 100 timesRp∘ minus Rp

Rp (8)

IE WLM () = 100 times CR minus CR∘

CR (9)

The calculated data for the percentage inhibition effi-ciency using weight loss method (WLM) potentiody-namic polarization-corrosion rate (PP-CR) linear polariza-tion resistance (LPR) and potentiodynamic polarization-corrosion current density (PP-119894corr) are presented in Figure 7All these parameters showed a similar trend From the resultit is evident that the IE () obtained by different methods


are in good agreement at all the concentrations of inhibitorstudied Similar result was documented in [35]

PP-119894corr The graphical trend shows that the variation of theconcentration does bring about a change in PP-119894corr valuehowever it is not dependent on the concentration linearrelationship was not observed

PP-CR The graphical trendregression analysis shows goodpolynomial relationship between the concentration and cor-rosion rate It can be inferred that the PP-CR is dependent onthe concentration

LPRThe regression analysis shows a polynomial relationshiphence one can infer that there is a stochastic relation betweenLPR and concentration

WLM The variation of the concentration does not bringabout any change in the weight loss

In summary from the results obtained one can deducethat the best inhibitor performance can be achieved at opti-mal concentration of 10 gmL for all parameters measured(PP-119894corr PP-CR LPR and WLM)

4 Conclusions

Theexperimental investigation of the use of ferrous gluconateas corrosion inhibitor in sodium chloride medium led to thefollowing deductions

(i) Ferrous gluconate acted as an effective corrosioninhibitor for aluminum alloy in sodium chlorideenvironment at 28∘C

(ii) It was established that the optimum concentration offerrous gluconate that should be used as corrosioninhibitor is 10 gmL at 28∘C

(iii) Polarization result shows that ferrous gluconate actedas amixed type corrosion inhibitor adsorption on thealuminum alloy surface obeys Langmuirrsquos adsorptionisotherm

(iv) The percentage inhibition efficiency obtained fromweight loss and potentiodynamic polarization tech-niques were found to correlate with each other

Acknowledgments

This work is supported financially by the National ResearchFoundation The authors also acknowledge the support fromTshwane University of Technology Pretoria South Africawhich helped to accomplish this work

References

[1] M Abdulwahab I A Madugu S A Yaro S B Hassan and AP I Popoola ldquoEffects of multiple-step thermal ageing treatmenton the hardness characteristics of A3560-type Al-Si-Mg alloyrdquoMaterials and Design vol 32 no 3 pp 1159ndash1166 2011

[2] M Metikos-Hukovic R Babic and Z Grubac ldquoThe studyof aluminium corrosion in acidic solution with nontoxic

inhibitorsrdquo Journal of Applied Electrochemistry vol 32 no 1 pp35ndash41 2002

[3] M A Amin H H Hassan O A Hazzazi and M M QhatanildquoRole of alloyed silicon and some inorganic inhibitors in theinhibition of meta-stable and stable pitting of Al in perchloratesolutionsrdquo Journal of Applied Electrochemistry vol 38 no 11 pp1589ndash1598 2008

[4] AMAl-Turkustani andMMAl-Solmi ldquoCorrosion inhibitionof aluminium in acidic solution by aqueous extract of ajowanplant as green inhibitorrdquo Journal of Asian Scientific Research vol1 pp 346ndash358 2011

[5] R Khandelwal S Sahu S K Arora and S P Mathur ldquoStudyof corrosion inhibition efficiency of naturally occurring plantcordial dicotoma on aluminium in acidic mediardquo Journal ofCorrosion Science and Engineering vol 13 2010 Preprint 12

[6] M Kliskic J Radosevic S Gudic and V Katalinic ldquoAqueousextract of Rosmarinus officinalis L as inhibitor of Al-Mg alloycorrosion in chloride solutionrdquo Journal of Applied Electrochem-istry vol 30 no 7 pp 823ndash830 2000

[7] C A Loto and A P I Popoola ldquoPlants extracts corrosioninhibition of aluminium alloy in H

2

SO4

rdquo Canadian Journal ofPure and Applied Sciences vol 6 pp 1973ndash1980 2012

[8] S S Abdel Rehim H H Hassan andM A Amin ldquoChronoam-perometric studies of pitting corrosion of Al and (Al-Si) alloysby halide ions in neutral sulphate solutionsrdquo Corrosion Sciencevol 46 no 8 pp 1921ndash1938 2004

[9] E McCafferty ldquoCompetitive adsorption model for the inhibi-tion of crevice corrosion and pittingrdquo Journal of the Electro-chemical Society vol 137 no 12 pp 3731ndash3737 1990

[10] P L Cabot F A Centellas E Perez and R Loukili ldquoPitting andrepassivation processes of AlZnMg alloys in chloride solutionscontaining sulphaterdquo Electrochimica Acta vol 38 no 18 pp2741ndash2748 1993

[11] G Blustein J Rodriguez R Romanogli and C F ZinolaldquoInhibition of steel corrosion by calcium benzoate adsorptionin nitrate solutionsrdquo Corrosion Science vol 47 no 2 pp 369ndash383 2005

[12] K C Emregul A Abdulkadir Akay and O Atakol ldquoThecorrosion inhibition of steel with Schiff base compounds in 2M HClrdquo Materials Chemistry and Physics vol 93 no 2-3 pp325ndash329 2005

[13] B Gao X Zhang and Y Sheng ldquoStudies on preparing and cor-rosion inhibition behaviour of quaternized polyethyleneiminefor low carbon steel in sulfuric acidrdquo Materials Chemistry andPhysics vol 108 no 2-3 pp 375ndash381 2008

[14] P B Raja andMG Sethuraman ldquoNatural products as corrosioninhibitor for metals in corrosive mediamdasha reviewrdquo MaterialsLetters vol 62 no 1 pp 113ndash116 2008

[15] A Singh and M A Quraishi ldquoAzwain (Trachy-Spermumcopticum) seed extract as an efficient corrosion inhibitor foraluminium in NaOH solutionrdquo Research Journal of RecentSciences vol 1 pp 57ndash61 2012

[16] R A Mohammed M Abdulwahab I A Madugu J OGaminana and F Asuke ldquoInhibitive effect by natural Cyperusesculentus L oil on the corrosion of A356 0-type Al-Si-Mgalloy in simulated seawater environmentrdquo Journal of MaterialEnvironmental Science vol 1 pp 93ndash98 2013

[17] P D R Kumari J Nayak and A N Shetty ldquo3-Methyl-4-amino-5-mercapto-124-triazole as corrosion inhibitor for 6061Al-15(Vol-) Sic (p) composite on 05M sodium hydroxide solu-tionrdquo Journal of Material Environmental Science vol 4 pp 387ndash402 2011


[18] R Li X Y Li J Pang et al ldquoPassivation behaviour ofAl88Fe6La6 glassy alloy in NaOH and H

2

SO4

solutionsrdquo Inter-national Journal of Electrochemical Science vol 8 pp 2983ndash2995 2013

[19] I C Madufor U E Itodoh M U Obidiegwu and MS Nwakaudu ldquoInhibition of aluminium corrosion in acidicmedium by chrysophyllum albidum (African star apple) fruitextractrdquo Journal of Engineering vol 2 pp 16ndash23 2012

[20] O K Abiola N C Oforka A O Ifelebuegu T M Fasinaand A I Babatunde ldquoEffect of diphenyl thiocarbazone anddiphenylcarbazone on acid corrosion of aluminium in HClsolution Part 1rdquo Journal of Scientific Research and Developmentvol 11 pp 1ndash8 2009

[21] P D Reena Kumari J Nayak and A Nityananda Shetty ldquo3-ethyl-4-amino-5-mercapto-124-triazole as corrosion inhibitorfor 6061-alloy in sodium hydroxide solutionrdquo Portugaliae Elec-trochimica Acta vol 29 no 6 pp 445ndash462 2011

[22] I O Arukalam and M U Obidiegwu ldquoThe inhibition ofaluminium corrosion in hydrochloric acid solution by hydrox-yethyl celluloserdquo Academic Research International vol 1 pp484ndash491 2011

[23] A P I Popoola O S I Fayomi and M Abdulwahab ldquoDegra-dation behaviour of aluminium in 2M HClHNO3 in thepresence of arachis hypogeae natural oilrdquo International Journalof Electrochemical Science vol 7 pp 5817ndash5827 2012

[24] I B Obot and N O Obi-Egbedi ldquoFluconazole as an inhibitorfor aluminium corrosion in 01MHClrdquoColloids and Surfaces Avol 330 no 2-3 pp 207ndash212 2008

[25] S J Garcıa T HMuster O Ozkanat et al ldquoThe influence of pHon corrosion inhibitor selection for 2024-T3 aluminium alloyassessed by high-throughput multielectrode and potentiody-namic testingrdquo ElectrochimicaActa vol 55 no 7 pp 2457ndash24652010

[26] S A Umoren and M M Solomon ldquoEffect of halide ionsadditives on the corrosion inhibition of aluminum in HCl bypolyacrylamiderdquoThe Arabian Journal for Science and Engineer-ing vol 35 pp 115ndash129 2010

[27] M A Amin S S Abd El Rehim and A S El-Lithy ldquoPitting andpitting control of Al in gluconic acid solutionsmdashpolarizationchronoamperometry and morphological studiesrdquo CorrosionScience vol 52 no 9 pp 3099ndash3108 2010

[28] O Sanni C A Loto and A P I Popoola ldquoElectrochemicalassessment of zinc gluconate as inhibitor onmild steel in a salineenvironmentrdquo Research on Chemical Intermediates 2013

[29] R Touir M Cenoui M El Bakri and M Ebn TouhamildquoSodium gluconate as corrosion and scale inhibitor of ordinarysteel in simulated cooling waterrdquo Corrosion Science vol 50 no6 pp 1530ndash1537 2008

[30] F Ivusic O Lahodny-Sarc andV Alar ldquoCorrosion inhibition ofcarbon steel in various water types by zinc gluconaterdquoMaterialvol 44 pp 319ndash329 2013

[31] O Lahodny-Sarc and S Popov ldquoCorrosion inhibition of mildsteel in sodium gluconate-borate solutionsrdquo Surface and Coat-ings Technology vol 34 no 4 pp 537ndash547 1988

[32] S A M Refaey ldquoPassivation and pitting corrosion of tin ingluconate solutions and the effect of halide ionsrdquo Journal ofApplied Electrochemistry vol 26 no 5 pp 503ndash507

[33] A Singh A K Singh and M A Quraishi ldquoDapsone a novelcorrosion inhibitor for mild steel in acid mediardquo The OpenElectrochemistry Journal vol 2 pp 43ndash51 2010

[34] E W Abel ldquoThe literature of inorganic chemistryrdquo in Com-prehensive Inorganic Chemistry II J C Bailar Ed PergamonOxford UK 1965

[35] R Rosliza ldquoImprovement of corrosion resistance of aluminiumalloy by natural productsrdquo in Corrosion Resistance H Shih Edpp 377ndash395 InTech 2012

[36] A Yagan N O Pekmez and A Yildiz ldquoCorrosion inhibitionby poly(N-ethylaniline) coatings of mild steel in aqueous acidicsolutionsrdquo Progress in Organic Coatings vol 57 no 4 pp 314ndash318 2006

[37] I Langmuir ldquoThe constitution and fundamental properties ofsolids and liquids Part I Solidsrdquo The Journal of the AmericanChemical Society vol 38 no 2 pp 2221ndash2295 1916

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MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


Table 1 Chemical composition of aluminium alloy (wt)

Si Fe Cu Mn Mg Cr Ti Ca Zr V Al0157 0282 00025 0024 051 0023 0006 00011 0002 00035 Balance

surface morphology of as-corroded uninhibited conditionshowed severe pits and damage formation than those of as-corroded inhibited conditions The authors concluded thatadditions of Arachis hypogaea as corrosion inhibitor foraluminumalloy indicate a high inhibition efficiency potentialvalue and polarization resistance with decrease in currentdensity The authors of [24] studied the interfacial behaviorof fluconazole (FLC) as a corrosion inhibitor for aluminumin hydrochloric acid solution between hydrochloric acidand aluminum using weight loss method The experimen-tal results revealed that fluconazole exhibits an excellentcorrosion inhibitor property for aluminum in hydrochloricacidic medium The authors of [25] worked on the effect ofsolution pH on the anticorrosion performance of differentinhibitors K

2Cr2O7 CeCl

3 and Ce(dbp)

3on aluminum

alloy (AA2024-T3) using themultielectrode and conventionalpotentiodynamic polarization methods The results showedthat the K

2Cr2O7at 10minus4M after 30min of exposure time

behaves as the best inhibitor across the studied pH rangeThe authors of [26] worked on the influence of bromideand iodide ions on the inhibitive effect of polyacrylamide(PA) on aluminum corrosion in HCl solution using weightloss hydrogen evolution and thermometric techniques at30 and 60∘C The experimental results show that the halideadditives synergistically increased the inhibition efficiency ofpolyacrylamide and the increase in inhibition efficiency wasfound to be more obvious in iodide than bromide ions

Gluconic acid occurs naturally in honey fruit kom-bucha tea and wine [27] They are environmentally suitablenontoxic compounds and gluconates are part of the suc-cessful commercial corrosion inhibitors Gluconic acid andits derivatives are used as ingredients in various hygienicproducts for scale removal in metal cleanings as householdcleaning compounds including mouth washer metal finish-ing and for water treatment operation Sodium calciumand zinc salts of gluconic acid have been reported to beeffective nontoxic inhibitors for tin iron and mild steel innear neutral solution [27ndash29] The efficiency of gluconateinhibition depends on pH value inhibitor concentrationchemical composition of investigated solution the nature ofcations introduced in the solution as gluconate and the stateof the metal surface [30] Different mechanisms of corrosioninhibition by gluconate were proposed It is speculated thatgluconate can repair the oxide film by its adsorption on theexposed metal surface in weak spots of porous oxide filmGluconates can be incorporated in the oxide film during itsformation andor gluconate are forming more or less solublecomplexes that can be precipitated on the metal surface [30]In view of this it is essential to study the corrosion behaviorof aluminum in ferrous gluconate solutionThe present studyaimed at evaluating the potential of ferrous gluconate as aninhibitor for aluminum alloy in saline medium using weightloss and potentiodynamic polarization methods

HO

HO

HO

HO

HO

O

O Ominus

Ominus

OH

OH

OH

OH

OH

Fe+2

Figure 1 Molecular structure of ferrous gluconate

2 Experimental

21 Materials and Sample Preparation Aluminum alloy withthe chemical composition presented in Table 1 was usedas substrate material for weight loss and potentiodynamicpolarization studies The aluminum alloy plate was cut usinga Struers cutting machine with a Discotom-5 cut-off wheelA Struers lubricant which works as a coolant was usedduring cutting The substrate was cut and machined todimensions 12 times 12 times 12mm The aggressive solution ofsodium chloride purchased from SMM Instruments (Pty)Ltd South Africa was used for this study The chemicalstructure of ferrous gluconate is shown in Figure 1 purchasedfrom SMM Instruments (Pty) Ltd South Africa An insulatedcopper wire was connected to one side of the sample usingan aluminum conducting tape and cold mounted in methylmethacrylate resin leaving one surface of an area of 1 cm2for potentiodynamic polarization measurement the exposedsurface area was abraded with different grates of emerypapers degreased with acetone rinsed in distilled waterdried weighed and stored in a desiccator The initial weightof the samples was taken and recorded In each experiment005M NaCl solution was prepared freshly as requiredCorrosion studies were carried out at 28∘C

22 Weight Loss Measurement The weight loss test wasconducted on the aluminum alloy weighed samples in theabsence and presence of different concentrations of inhibitorat 28∘C Volume of the solution used was 200mL and theconcentration of the inhibitor was in the range of 05 1015 and 20 gmL in saline environment The samples werewashed with distilled water dried in acetone and weighedat an interval of 48 hours of immersion time Corrosion








Corrosionpotential

(V)





876119882

119863119860119879

(1)





(2)






0

005

01

015

02

025

03

2 4 6 8 10 12 14 16 18 20 22 24 26 28

Cor

rosio

n ra

te (m

my

r)


Control

minus005

05 FG1 FG

15 FG2 FG



119886and 120573

119888) with




0

20

40

60

80

100

120

2 4 6 8 10 12 14 16 18 20 22 24 26 28

Inhi

bitio

n effi

cien

cy (

)


05 FG1 FG

15 FG2 FG





Pote

ntia

l (V

)

Control

minus2

minus15

minus1

minus05

0

05

1

15

2


05FG10FG

15FG20FG




119886and 119887119888values








Spectrum 3

(a)


Spectrum 5

(b)


0

05

1

15

2

25

05 1 15 2

y = 05x

R2 = 1

C120579

C (gmL)



4Al + 3O2+ 6H2O 997888rarr 4Al(OH)

3 (5)


2



0

20

40

60

80

100

05 1 15 2

IE (

)

LPRWLM

C (gmL)

PP-icorrPP-CR






80

85

90

95

100

105

05 1 15 2

IE (

)

C (gmL)

y = minus16075x2 + 1034x + 83573

R2 = 07873

PP-CR

PP-CRPoly ( )PP-CR

(a)

80

82

84

86

88

90

92

94

96

98

100

102

05 1 15 2

y = minus07175x2 + 55325x + 88033

R2 = 04065

C (gmL)

IE (

)

PP-icorr

Poly ( )PP-icorr

PP-icorr

(b)

965

97

975

98

985

99

995

100

1005

05 1 15 2

LPR

LPRPoly (LPR)

y = minus0385x2 + 2515x + 95885

R2 = 07352

C (gmL)

IE (

)

(c)




∘

corr119894corr (6)


CR (7)


Rp (8)


CR (9)









4 Conclusions






Acknowledgments


References









2

SO4














2

SO4




























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










Corrosionpotential

(V)





876119882

119863119860119879

(1)





(2)






0

005

01

015

02

025

03

2 4 6 8 10 12 14 16 18 20 22 24 26 28

Cor

rosio

n ra

te (m

my

r)


Control

minus005

05 FG1 FG

15 FG2 FG



119886and 120573

119888) with




0

20

40

60

80

100

120

2 4 6 8 10 12 14 16 18 20 22 24 26 28

Inhi

bitio

n effi

cien

cy (

)


05 FG1 FG

15 FG2 FG





Pote

ntia

l (V

)

Control

minus2

minus15

minus1

minus05

0

05

1

15

2


05FG10FG

15FG20FG




119886and 119887119888values








Spectrum 3

(a)


Spectrum 5

(b)


0

05

1

15

2

25

05 1 15 2

y = 05x

R2 = 1

C120579

C (gmL)



4Al + 3O2+ 6H2O 997888rarr 4Al(OH)

3 (5)


2



0

20

40

60

80

100

05 1 15 2

IE (

)

LPRWLM

C (gmL)

PP-icorrPP-CR






80

85

90

95

100

105

05 1 15 2

IE (

)

C (gmL)

y = minus16075x2 + 1034x + 83573

R2 = 07873

PP-CR

PP-CRPoly ( )PP-CR

(a)

80

82

84

86

88

90

92

94

96

98

100

102

05 1 15 2

y = minus07175x2 + 55325x + 88033

R2 = 04065

C (gmL)

IE (

)

PP-icorr

Poly ( )PP-icorr

PP-icorr

(b)

965

97

975

98

985

99

995

100

1005

05 1 15 2

LPR

LPRPoly (LPR)

y = minus0385x2 + 2515x + 95885

R2 = 07352

C (gmL)

IE (

)

(c)




∘

corr119894corr (6)


CR (7)


Rp (8)


CR (9)









4 Conclusions






Acknowledgments


References









2

SO4














2

SO4




























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0

20

40

60

80

100

120

2 4 6 8 10 12 14 16 18 20 22 24 26 28

Inhi

bitio

n effi

cien

cy (

)


05 FG1 FG

15 FG2 FG





Pote

ntia

l (V

)

Control

minus2

minus15

minus1

minus05

0

05

1

15

2


05FG10FG

15FG20FG




119886and 119887119888values








Spectrum 3

(a)


Spectrum 5

(b)


0

05

1

15

2

25

05 1 15 2

y = 05x

R2 = 1

C120579

C (gmL)



4Al + 3O2+ 6H2O 997888rarr 4Al(OH)

3 (5)


2



0

20

40

60

80

100

05 1 15 2

IE (

)

LPRWLM

C (gmL)

PP-icorrPP-CR






80

85

90

95

100

105

05 1 15 2

IE (

)

C (gmL)

y = minus16075x2 + 1034x + 83573

R2 = 07873

PP-CR

PP-CRPoly ( )PP-CR

(a)

80

82

84

86

88

90

92

94

96

98

100

102

05 1 15 2

y = minus07175x2 + 55325x + 88033

R2 = 04065

C (gmL)

IE (

)

PP-icorr

Poly ( )PP-icorr

PP-icorr

(b)

965

97

975

98

985

99

995

100

1005

05 1 15 2

LPR

LPRPoly (LPR)

y = minus0385x2 + 2515x + 95885

R2 = 07352

C (gmL)

IE (

)

(c)




∘

corr119894corr (6)


CR (7)


Rp (8)


CR (9)









4 Conclusions






Acknowledgments


References









2

SO4














2

SO4




























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





Spectrum 3

(a)


Spectrum 5

(b)


0

05

1

15

2

25

05 1 15 2

y = 05x

R2 = 1

C120579

C (gmL)



4Al + 3O2+ 6H2O 997888rarr 4Al(OH)

3 (5)


2



0

20

40

60

80

100

05 1 15 2

IE (

)

LPRWLM

C (gmL)

PP-icorrPP-CR






80

85

90

95

100

105

05 1 15 2

IE (

)

C (gmL)

y = minus16075x2 + 1034x + 83573

R2 = 07873

PP-CR

PP-CRPoly ( )PP-CR

(a)

80

82

84

86

88

90

92

94

96

98

100

102

05 1 15 2

y = minus07175x2 + 55325x + 88033

R2 = 04065

C (gmL)

IE (

)

PP-icorr

Poly ( )PP-icorr

PP-icorr

(b)

965

97

975

98

985

99

995

100

1005

05 1 15 2

LPR

LPRPoly (LPR)

y = minus0385x2 + 2515x + 95885

R2 = 07352

C (gmL)

IE (

)

(c)




∘

corr119894corr (6)


CR (7)


Rp (8)


CR (9)









4 Conclusions






Acknowledgments


References









2

SO4














2

SO4




























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




80

85

90

95

100

105

05 1 15 2

IE (

)

C (gmL)

y = minus16075x2 + 1034x + 83573

R2 = 07873

PP-CR

PP-CRPoly ( )PP-CR

(a)

80

82

84

86

88

90

92

94

96

98

100

102

05 1 15 2

y = minus07175x2 + 55325x + 88033

R2 = 04065

C (gmL)

IE (

)

PP-icorr

Poly ( )PP-icorr

PP-icorr

(b)

965

97

975

98

985

99

995

100

1005

05 1 15 2

LPR

LPRPoly (LPR)

y = minus0385x2 + 2515x + 95885

R2 = 07352

C (gmL)

IE (

)

(c)




∘

corr119894corr (6)


CR (7)


Rp (8)


CR (9)









4 Conclusions






Acknowledgments


References









2

SO4














2

SO4




























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










4 Conclusions






Acknowledgments


References









2

SO4














2

SO4




























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





2

SO4




























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



research article inhibitive action of ferrous gluconate on aluminum alloy...

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