research article bee wax propolis extract as eco-friendly...

Research ArticleBee Wax Propolis Extract as Eco-Friendly CorrosionInhibitors for 304SS in Sulfuric Acid

Femiana Gapsari Rudy Soenoko Agus Suprapto and Wahyono Suprapto

Mechanical Engineering Department Faculty of Engineering Brawijaya University Jalan MT Haryono 167 Malang 65145 Indonesia

Correspondence should be addressed to Femiana Gapsari femianagapsarigmailcom and Rudy Soenoko rudysoenyahoocom

Received 16 June 2015 Revised 27 August 2015 Accepted 30 August 2015

Academic Editor Ramazan Solmaz

Copyright copy 2015 Femiana Gapsari et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

The inhibition properties of bee wax propolis (BWP) extract on the 304SS in 05M sulfuric acid were conducted using potentio-dynamic polarization EIS and XRD Quercetin (2-(34-dihydroxy phenyl)-357-trihydroxy-4H-chromen-4-one) was identified asthe main compound in the BWP extract based on FTIR and HPLC analysis The results showed that the inhibitor could retard thecorrosion rate of 304SS in 05M sulfuric acidwhich reached 9729 and 9142 at 2000 ppmbased on potentiodynamic polarizationand EIS measurement respectively The inhibition efficiency decreased with increasing temperature The inhibition mechanism ofBWP extract on the 304SS was physisorption and obeyed Temkin adsorption isotherm equation The thin protective layer on the304SS surface was confirmed by XRD

1 Introduction

Stainless Steel (SS) type 304 is widely used as the main con-struction in the nuclear petroleum energy food and medi-cine industry as well as the electrochemical industry [1] The304SS can be applied in various fields of industry and non-industry compared to other types It has high corrosion resis-tance in aggressive environments especially under high tem-perature conditions on gas environmentThe corrosion resis-tance is from stable chrome oxide layer on the metal surfacethat protects themetal fromcorrosive environment attack [2]

The acid pickling cleaning and descaling and also oilacidizing are meant to remove the dirt scale and rust onsteelThe process uses strong acids such as hydrochloric acid(HCl) and sulfuric acid (H

2SO4) in various concentrations

[3] However the high reactivity of sulfuric acid can causethe 304SS to be corrodedThis is due to the dissolution of theprotective layer of chromiumoxide containing nickel directlyTherefore the corrosion was controlled by using inhibitorThis was done because it is a simple application and has noeffect on the production process [4] The use of inhibitors ingeneral has been widely studied to solve a metal corrosionproblem in acid solution [5ndash11] Inhibitors are substances that

can reduce and prevent the metal reaction in its environmentwith a very small amount [12ndash16]

Formerly inhibitors which were widely used were inor-ganic inhibitors However inorganic inhibitors have a lot ofdisadvantages The salts form of chromate compounds hashigh toxicity that is harmful to the environment Anotherinorganic inhibitor is titanium (IV) oxide (TiO) that is rarelyused because of being very expensive Moreover inorganicinhibitors have characteristics that increase the corrosion rateif used in excess amount [17] Therefore the use of inorganicinhibitors has been replaced by organic inhibitors which aremore eco-friendly cheaper and easier to obtain [18ndash25] Theefficient inhibitors are organic compounds that contain elec-tronegative atom (ie N S or O) or double bond in theirstructure [26ndash28] Unfortunately the synthetic organic com-pounds can be toxic and hazardous for environment so todaymany researchers use organic compounds fromnaturalmate-rials as inhibitor Organic inhibitors from natural materialused are part of the plant [29] such as extract of the leaves [518] seeds [19] fruit [20] and rod [21] Aside from the parts ofplants honey is also a natural material that have been reportedto be good for retarding the corrosion rate of copper carbonsteel alloys and aluminum in salt environment [15 24 25]

Hindawi Publishing CorporationInternational Journal of CorrosionVolume 2015 Article ID 567202 10 pageshttpdxdoiorg1011552015567202

2 International Journal of Corrosion

Honey is a natural result that is processed by bees fromthe nectar of flower or plant parts However the price ofhoney is expensive and it is commonly used as the drugmakes it nonefficient as an inhibitor on an industrial scaleTherefore we use the bee wax propolis (BWP) extract asinhibitor in the present study The BWP is a waste ofhoneycomb and contains a compound similar to honey soit is possible to be used as a corrosion inhibitor The presentstudy is devoted to investigation of the inhibition efficiencyof the BWP extract for corrosion of 304SS in 05MH

2SO4

solution The corrosion measurement was performed by anelectrochemical methodThe influence of temperature on theinhibition efficiency and mechanism of inhibition and theformation of a passive layer will also be discussed

2 Materials and Methods

21 Sample Preparation Extraction and Inhibitor Character-istics The 304SS in the present study had chemical composi-tion (wt) 004 C 052 Si 092 Mn 0030 P 0002S 958 Ni 1815 Cr and bal Fe The 304SS specimenswith 02mm times 1 cm times 1 cm dimension were prepared forthe working electrode (WE) The WE was added to epoxyresin with a geometric exposed surface area measuring 1 cm2and connected to the electrolyte Before the experiment thespecimen surface was polished with emery paper of grades400 to 1200 consecutively

The BWP is used as honeycomb waste that had beensqueezed 3-4 times These wastes were usually in the formof wax and remaining of sticky honey The BWP wasextracted by liquid-liquid method in order to obtain theoptimum conditions The extract of BWP was characterizedby Fourier Transform Infrared Spectroscopy (FTIR) andHigh Performance Liquid Chromatography (HPLC) FTIRanalysis aims to determine the functional groups containedin the BWP extract FTIR spectra showed the characteristicwavenumber of flavonoids which were a carbonyl group(C=O ketone) at 171267 cmminus1 OH at 336748 cmminus1 andaromatic group at 164902 151402 and 146001 cmminus1 Iden-tification of the main compounds in the BWP extract wasfollowed by HPLC analysis The result of HPLC identifica-tion showed that quercetin (2-(34-dihydroxyphenyl)-357-trihydroxy-4H-chromen-4-one) was the greatest compoundin the BWP extract

22 Electrochemical Measurement Standard ASTM (Amer-ican Standard and Testing) G31 was the reference used inthis measurement [31] One batch contained 05M sulfuricacid solution in various concentrations of BWP extractThere were 7 batches with BWP extract composition asfollows 0 1000 2000 3000 4000 5000 and 6000 ppmThe tests were carried out at room temperature (298K) Theoptimum concentration obtained from the measurement ofroom temperature was later tested at temperature variations(298 308 318 and 328K) Electrochemical measurementwas carried out at room temperature using an AutolabPGSTAT128N The optimum concentration of inhibitor wastested at temperature variations (298 308 318 and 328K)Specimens that have been prepared were then assembled into

an electrochemical cell with AgAgCl (3MKCl) as referenceelectrode (RE) and platinum as an auxiliary electrode (AE)and then immersed in a batch for 30 minutes The startingpotential was minus10 V and the scan rate range extended up+10V at Open Circuit Potential (OCP) with voltage scan rateof 0001 Vs Inhibition efficiency is calculated by [7 25 32]

IE =

119868corr minus 119868corr(119894)

119868corrtimes 100 (1)

where 119868corr and 119868corr(119894) are corrosion current density inmedium without and with the addition of inhibitors

TheElectrochemical Impedance Spectroscopy (EIS)mea-surement was conducted in the range frequency from 1000to 1Hz with amplitude of 15mA peak-to-peak AC signalgalvanostatically at the OCP The working electrode wasimmersed in the test solution for 30 minutes to establishconstant signal at open circuit potential Inhibition efficiencyusing EIS method was formulated by [7 33]

IE =

119877ct(119894) minus 119877ct

119877ct(119894)times 100 (2)

where 119877ct dan 119877ct(119894) are the resistance of the charge transfermedium without and with the addition of inhibitors Theimpedance parameters were calculated by fitting the exper-imental result to equivalent circuit using NOVA 17 software

3 Results and Discussion

31 pH Measurement There were no significant changes inpH by the addition of various concentrations of inhibitorTheaverage pH value of the solution without inhibitor was 15with 3 replicationsThe presence of inhibitor (1000 2000 and3000 ppm) in solution gives the average pH value of 148 147and 144 respectively

32Potentiodynamic PolarizationMeasurements Data obtainedfrom polarization are used to analyze the adsorption mecha-nism [10]Thepolarization curves obtainedwere extrapolatedto calculate corrosion parameters such as 119868corr 119864corr 120573119886 and120573119888[19 24] Figures 1(a) and 1(b) show the Tafel plots for 304SS

in 05MH2SO4without and with various concentrations of

inhibitor and the representative of the extrapolation exampleof Tafel plot for 304SS in 05MH

2SO4solution respec-

tively The results of extrapolation of Tafel plots are shown inTable 1

The optimum IE was 9727 which was gained onthe addition of 2000 ppm (Table 1) These results indicatedthat the corrosion rate of 304SS can be inhibited effectivelywith the increase of concentration that reached 2000 ppmIncreasing of IE value is proportional to decreasing ofcurrent density Data obtained from polarization are usedto analyze the adsorption mechanism [24] At concentrationof 2000 ppm the smallest current density was produceddue to the uniform adsorption of inhibitor molecules onmetal surfaces Optimum inhibition efficiency obtained ata concentration of 2000 ppm and decreased with increasingconcentration of inhibitor was suspected physical adsorption

International Journal of Corrosion 3

Table 1 Inhibition efficiency calculation of polarization measurements

Concentration of inhibitor (ppm) 120573119886(Vdec) 120573

119888(Vdec) 119864corr (V) 119868corr (Acm

2) IE ()0 0059 minus7958 minus0286 219 times 10minus5 mdash1000 0224 minus0794 minus0033 267 times 10minus6 87792000 0103 0172 minus0001 593 times 10minus7 97293000 0062 0359 minus0278 797 times 10minus6 63604000 0082 minus0707 minus0280 832 times 10minus6 61995000 0053 0033 minus0301 977 times 10minus6 55386000 0079 minus0177 minus0279 172 times 10minus5 2164

6000ppm5000ppm4000ppm

3000ppm2000 ppm1000 ppm0ppm

minus7 minus6 minus5 minus4minus8log I (Acm2)

minus04

minus03

minus02

minus01

00

01

E(V

) (A

gA

gCl (3

M K

Cl))

(a)

Experimental cathodic

Experimental anodic

Extrapolated cathodic

Calculated anodic Tafel line

minus040

minus035

minus030

minus025

minus020

minus015

minus65 minus60 minus55 minus50 minus45 minus40 minus35minus70log I (Acm2)

Ecorr

Icorr

E(V

) (A

gA

gCl (3

M K

Cl))

(b)

Figure 1 (a) Tafel plots with various concentrations of inhibitor and (b) extrapolarization of Tafel plot for 304SS in 05MH2SO4solution

mechanism [35] When the inhibitor addition is more thanthe optimum concentration the solution will be saturatedThere is possibility for strong interaction between inhibitormolecules in the solution and inhibitor which was attachedin the surface of metal so that this layer will be releasedagain into solution [36] According to Table 1 anodic Tafelconstants (120573

119886) and cathodic Tafel constants (120573

119888) are shown to

be irregular Irregularity of 120573119886and 120573

119888showed that the BWP

extract was a mixed inhibitor that modify the mechanism ofanodic dissolution and cathodic hydrogen evolution [9 37]

The assumption of physisorption can be confirmed bythe polarization measurement at temperature variations(Figure 2) Certainty is indicated by decreased inhibition effi-ciency with increasing temperature (Table 2) Physisorptionshowed the relatively weak dipoles interactions and couldcause desorption of BWP extract from the metal surface athigh temperature [1 5] Based on [38 39] IE decrease withincreasing temperature indicated that inhibitor moleculeswere physically adsorbed on metal surfaces Increasing oftemperature was likely initiated to stop the interaction andthe inhibition was not absorbed in the metal surface thatcaused decreases in inhibition efficiency

2000 ppm at 328K2000 ppm at 318K2000 ppm at 308K2000 ppm at 298K

0ppm at 328K0ppm at 318K0ppm at 308K0ppm at 298K

minus04

minus03

minus02

minus01

00

01

minus6minus7 minus5 minus4 minus3 minus2minus8log I (Acm2)

E(V

) (A

gA

gCl (3

M K

Cl))

Figure 2 Tafel plots of 304SS in the sulfuric acid 05M without andwith inhibitor at temperature variations


Table 2 The potentiodynamic polarization data of 304SS in the sulfuric acid 05M without and with inhibitor at temperature variations

Concentration of inhibitor (ppm) Temperature (K) 120573119886(Vdec) 120573


2) IE ()

0

298 0059 minus7958 minus0286 219 times 10minus5 mdash308 0057 minus0739 minus0297 712 times 10minus5 mdash318 0051 minus0106 minus0387 175 times 10minus3 mdash328 0148 0342 minus0339 404 times 10minus3 mdash

2000

298 0103 0172 minus0001 593 times 10minus7 9729308 0052 minus0186 minus0233 137 times 10minus5 8073318 0036 0097 minus0324 060 times 10minus3 6548328 0101 1399 minus0353 277 times 10minus3 3129

Table 3 Activation energy value

Concentration of inhibitor (ppm) 119864119886(kJmol)

0 151212000 23393

lnI c

orr

R2 = 0957

R2 = 0987

0ppm2000 ppm

31 32 33 3430

minus14

minus12

minus10

minus8

minus6

minus4

1T (10minus3 Kminus1)

Figure 3Arrhenius plots of 304SS in 05MH2SO4without andwith

inhibitor addition

Arrhenius equation is

ln 119868corr = ln119860 minus

119864119886

119877

(

1

119879

) (3)

The effect of temperature towards the corrosion rate canbe expressed by Arrhenius equation (3) The Arrheniusequation associated with an activation energy (119864

119886) which is

the minimum energy needed for the reaction to occur Thevalue of119864

119886can be obtained from the slope of linear regression

result between ln 119868corr and 1119879 (Figure 3) Calculation of 119864119886

valuewith inhibitor is higher thanwithout inhibitor (Table 3)The higher energy activation means that reaction occursslowly and its corrosion rates are sensitive to temperature [2140] As a consequence the inhibition process of BWP extracton 304SS surface is difficult to occur at high temperature and

tends to cause desorption [21 41] Besides that the higher 119864119886

value with inhibitor also showed BWP extract inhibition on304SS corrosion reaction via adsorption [6 42 43] It is asso-ciated with increased passive layer formed on the corrosionprocess [44]The result of 119864

119886value is in good agreement with

those obtained from the potentiodynamic polarization andreinforces the physisorption on the 304SS surface by inhibitormolecule The relationships between IE temperature and119864119886value are classified into three groups [6 45 46]

(1) IE decreases with increase of temperature 119864119886(solu-

tion with inhibitor) gt 119864119886(blank solution)

(2) IE increase with increase of temperature 119864119886(solu-

tion with inhibitor) lt 119864119886(blank solution)

(3) IE does not change with change of temperature 119864119886

(solution with inhibitor) = 119864119886(blank solution)

Based on the result of Tables 2 and 3 the inhibitor in this study(ie BWP extract) was included in the first group

33 Adsorption Isotherm of BWP Extract In general organicmolecules can inhibitmetal corrosion bymeans of adsorption[25] that occurs depending on the chemical compositionof molecule temperature and electrochemical potential onmetal or interface solutionmetal [22] Organic compoundsare mixed inhibitors that inhibit both the anodic and thecathodic reactions [9 18 22] Information of inhibitoradsorption on metal surface can be shown by adsorption iso-therm [5 7] The adsorption isotherm is based on potentio-dynamic polarization data The adsorption isotherm of thisstudywas calculatedwith some equations these are FrumkinLangmuir Temkin Freundlich Bockis-Swinkels and Flory-Huggins [47] The best fitted result of this study is obeyingthe Temkin adsorption isotherm equations (4) [11 48] whichis shown in Figure 4

Temkin equation is

log 120579

119862

= log119870 minus 119892120579 (4)

where 119862 is the concentration of BWP extract 120579 is the degreeof surface coverage 119892 is adsorbate parameter and 119870 is theadsorption equilibrium constant Based on (4) the value of119870 was calculated as 69183


Table 4 Thermodynamic parameters for 304SS in 05M H2SO4

without and with inhibitor

Concentration ofinhibitor (ppm) Δ119866

∘

ads (kJmol) Δ119867∘ (kJmol) Δ119878

∘ (JmolsdotK)

0 mdash 15057 169692000 minus2044 23471 42489

R2 = 0912

minus18

minus16

minus14

minus12

minus10

minus08

minus06

minus04

minus02

00

02 04 06 08 1000120579

log 120579

C

Figure 4 Temkin isotherm for the adsorption of BWP extract on304SS surface

119870 is related to the free energy of adsorption by [20]

119870 =

1

555

exp(minusΔ119866∘

ads119877119879

) (5)

where Δ119866∘ads is standard free energy of adsorption The valueof 555 is the concentration of water in solution expressedin mol Generally values of free energy of adsorption upto minus20 kJmol are consistent with electrostatic interactionbetween charged molecules and a charged metal (whichindicates physisorption) while those more negative thanminus40 kJmol involve charge sharing or transfer from theinhibitor molecules to the metal surface to form a coordinatetype of bond (which indicates chemisorption) [20 45] TheΔ119866∘

ads value in this study (Table 4) is characteristic for physi-sorption The negative values for Δ119866∘ads ensure the spontane-ity of the adsorption of BWP on 304SS surface [7 20 33]This result supports the fact that adsorption of BWP extract isphysisorption and that it is in a good agreement with theexplanation in Section 32

The values of enthalpy of activation (Δ119867∘) and entropy ofactivation (Δ119878∘) are calculated from a slope (minusΔ119867∘119877) and anintercept (ln(119877119873ℎ)+Δ119878∘119877) of linear plot in Figure 5 by [37]

119868corr = (

119877119879

119873ℎ

) exp(Δ119878∘

119877

) exp(minusΔ119867∘

119877

) (6)

where ℎ is Planckrsquos constant 119873 is Avogadrorsquos number 119879 isthe absolute temperature and 119877 is the universal gas constantCalculation of the value of Δ119867∘ and Δ119878

∘ is summarized inTable 4 The positive value of Δ119867∘ means the endothermic

305 310 315 320 325 330 335 340

R2 = 0946

R2 = 0981

0ppm2000 ppm

minus22

minus20

minus18

minus16

minus14

minus12


ln(I

corr

T)

Figure 5 Arrhenius plot for ln(119868corr119879) versus 1119879 in 05MH2SO4

without and with inhibitor addition

nature of metal dissolution process in the presence of theBWP extract [20 37]The positive value ofΔ119878∘means that theadsorption process is accompanied by an increase in entropywhich is the driving force for the adsorption of inhibitor ontothe metal surface [45]

34 EIS Measurement The parameters obtained from themeasurement of EIS are the charge transfer resistance (119877ct)Warburg impedance (W) solution resistance (119877

119904) and con-

stant phase element (CPE) Figure 6(a) shows the Nyquistplots for 304SS in 05MH

2SO4solution without and with

inhibitorThe interaction betweenmetal surface and solutioncauses a charge transfer between both of them measured as119877ct [11]The semicircle of Nyquist plot (Figure 6(a)) indicatedthe characteristic of roughness and inhomogeneity electrodesurface [8 49 50] Moreover that semicircle in the highfrequency region is attributed to the time constant whichis related to both 119877ct and CPE [51] Warburg impedancewas showed by a straight-line in low frequency W indicatescorrosion reaction within diffusion control that may occurdue to the diffusion of reactive species [52] The equivalentcircuit model (Figure 6(a)) illustrates the general case of thefrequency response of an interface characterized by chargetransfer and diffusion process [51 53 54] In the general fre-quency the polarization resistance consists of charge transferresistance (119877ct) and another resistance such as diffuse layerresistance accumulated species at metalinterface solutionand inhibitor film resistance [55]TheCPE indicate a differentphysical phenomenon such as surface inhomogeneity fromsurface roughness inhibitor adsorption and formation oflayer [56 57]

The responses of frequency of these equivalent circuitmodels (Figure 6(a)) depend on the value of charge transferresistance (119877ct) and diffusion resistance (W)That equivalentcircuit model used to fit the result of EIS measurement with


Table 5 Fitting results of EIS data for 304SS in 05M H2SO4without and with inhibitor

Concentration of inhibitor (ppm) 119877119904(Ω cm2) 119877ct (Ω cm2) CPE (120583Fcm2) 119899

W119884119882(Ωminus1 cmminus2 s05) 120594

2 IE ()

0 803 2496 37765 0996 00691 00141 mdash1000 1135 23750 6211 1003 00029 10555 89492000 1186 29084 5995 1001 00020 11640 91423000 1015 26775 5994 1001 00021 09351 90684000 859 25796 6335 1001 00026 09171 90325000 835 24238 6804 1002 00031 08045 89706000 799 19639 6793 1003 00042 09013 8729

W

CPE



Rct

Rs

200 400 600 8000Z998400 (Ω cm2)

0

100

200

300

400

minusZ998400998400

(Ωcm

2)

Z998400 (Ω)

0

8

minusZ998400998400

(Ω)

(a)

ExperimentalSimulation

10 20 30 40 500Z (Ω cm2)

0

5

10

15

minusZ998400998400

(Ωcm

2)

(b)

Figure 6 (a) Nyquist plots of 304SS in 05MH2SO4with variations of inhibitor concentration and equivalent circuit model used to fit the

Nyquist plots and (b) a representative of fitting example of Nyquist diagrams for 304SS in 05MH2SO4solution

a representative of fitting example of Nyquist diagrams for304SS in 05MH

2SO4solution is shown in Figure 6(b)

Fitting of the experimental result from EIS to equivalentcircuit gave all parameters impedance that is summarized inTable 5

The 119877ct value indicates the amount of inhibition fromthe BWP extract addition [18 58] The diameter of capacitivecircle (Figure 6(a)) with inhibitor is larger than that withoutinhibitor where the largest diameter was obtained at theinhibitor concentration of 2000 ppmThe diameter of capac-itive circle which increased at inhibitor 2000 ppm indicatedthat BWP extract increased the charge transfer resistanceand gave an inhibition effect on the 304SS corrosion in05MH

2SO4[51] Increasing of the 119877ct value with inhibitor

addition of 2000 ppm gave a better performance to retardcorrosion because of the oxide layer formation [8 11 53]

The inhibition efficiency (IE) from this method reached9142 (Table 5) which is in a good agreement with thepotentiodynamic polarization method

35 Mechanism of Corrosion Inhibition Inhibitor can retardthe corrosion rate of metal in various ways one of them is viaadsorption process Adsorption retards the corrosion rate byincreasing or decreasing the reactant diffusion rate to surfacemetal and by reducing the electric resistance from the metalsurface [13 19] Based on the potentiodynamic polarizationmeasurement the IE decrease with increasing temperatureindicates that physisorption occurred on 304SS surface byinhibitormoleculeThe increasing of119877ct value and decreasingof CPE value also showed adsorption process The quercetin(Figure 7(a)) as main compound of the BWP extract hasactive sites in form of 119901 electron of O atom and 120587 bond of


O

OOH

HO

OH

OH

OH

(a)

Fe Fe Fe Fe

Interaction with the aromatic 120587-electronsInteraction with the p-electrons

+ + + +

(b)

Figure 7 (a) Chemical structure of quercetin and (b) interaction of quercetin active sites with the 304SS surface [30]

aromatic rings [30] that can interact with the vacant 119889 orbitalof Fe as shown in Figure 7(b) Those interactions will formthin protective layer (Fe-quercetin complex) which protectthe 304SS from the aggressiveness of sulfuric acid

The result of X-ray diffraction (XRD) on Figure 8 showsthe presence of Fe

2O3and Cr

2O3 in testing solution either

without or with inhibitor addition There was a smoothsurface on metal surface to prevent the corrosion of 304SSthrough adsorption of the inhibitors on metal surface [2359] At solution without inhibitor actually the 304SS haspassive layer (in the form of Cr

2O3which contains Ni) that

directly contacts with the solution and caused concentrationof Cr3+ and Ni2+ ions to increase At this condition Fe is stillbeing protected by that passive layer Longer contact with thesolutionmay cause theCr3+ ion to decompose completely andFe will be oxidized [60] The testing solution with inhibitorshows that the presence of Fe

2O3and Cr

2O3peaked at angle

of 2120579 = 44482 and 75374 that was related to (minus4 0 0)and (6 2 2) planes respectively The intensity of Cr

2O3

peak in solution with inhibitor is lower than that withoutinhibitor This shows that Cr

2O3has dissolved more and

cannot protect the 304SS from the aggressiveness of sulfuricacid therefore the bigger Fe

2O3(5334) was formed That

Cr2O3passive layer is changed by a thin protective layer

as the result of inhibitor molecule adsorption on the 304SSsurface That thin protective layer is shown by the presenceof Fe-CHO peak at angle 2120579 = 42267 that was related to(1 1 1) plane At the interface of metalacid solution thedissolution of iron will produce Fe2+ ion such as explained by

o

o b

a

Fe-CHO

lowast

lowast

o Cr2O3

10 20 30 40 50 60 70 80 90 10002120579

lowast Fe2O3

Figure 8 X-ray diffraction patterns of 304SS in 05MH2SO4with-

out (a) and with (b) inhibitor at temperature 298K

Garai et al (2012) [59] Inhibitor molecules adsorb on the304SS surface and replace water molecules by transformingto higher stable iron-inhibitor complex [59] The formationof this complex has also been confirmed by EIS


Table 6 Properties of honey derivatives as corrosion inhibitor

Media Substrate Method Max IE () Ref05 NaCl Copper Weight loss potentiostatic polarization 8900 [11]Aqueous and 3 NaCl Tin Potentiostatic polarization 9000 [16]High saline water Carbon steel Weight loss potentiostatic polarization 9123 [24]35 NaCl Aluminium alloy Potentiodynamic polarization EIS measurement and DEIS measurement 7300 [25]05 NaCl CuNiFe alloy Potentiodynamic polarization EIS measurement 7006 [34]

The results of investigation have shown that BWP extractact as good corrosion inhibitor for 304SS in 05M sulfuricacid Similar results were obtained using honey derivativeas inhibitor in corrosion investigation on carbon steel [15]copper [24] aluminium [25] and CuNiFe [34] alloy in saltenvironment Moreover other investigations reported thatthe synergistic effect between honey and black radish juiceincreased the inhibition efficiency on corrosion of tin in aque-ous and sodium chloride [16] The observation that we con-ducted in the present study was in sulfuric acid solutionwhich makes it different to investigations There were differ-ences of inhibition efficiency due to the chemical compositionof honey derivatives The comparisons of the investigationsresult were listed in Table 6

4 Conclusions

(1) The extract of bee wax propolis (BWP) acts as goodinhibitor for corrosion process of 304SS in 05Msulfuric acid solution

(2) The optimum inhibition efficiency is 9729 and9142 at 2000 ppm using potentiodynamic polariza-tion and EIS measurement respectively

(3) The effect of temperature revealed physisorption forthe inhibition properties of the BWP extract and itobeyed Temkin adsorption isotherm

(4) Calculation of the Δ119866∘ads value (minus2044 kJmol) alsosupports the case of physisorption by BWP extract onthe 304SS surface

(5) A thin protective layer formedwas confirmed byXRDanalysis where there is the presence of Fe-CHO peakin the solution with inhibitor addition

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors are grateful to Dr rer nat Fredy Kurniawan asthe Head of Laboratory of Instrumentation and AnalyticalSciences Institut Teknologi Sepuluh Nopember SurabayaIndonesia for the use of laboratory facilitiesThe authors alsothank Kartika A Madurani for all her support and technicalassistance

References

[1] A S Fouda and A S Ellithhy ldquoInhibition effect of 4-phenyltia-zole derivatives on corrosion of 304L stainless steel in HCl solu-tionrdquo Corrosion Science vol 52 pp 868ndash875 2009

[2] C H Musinoi Hagen The Influence of Alternating Current onthe Polarization Behavior of Stainless Steel Department ofMate-rials Science and Engineering NTNU-Trondheim NorwegianUniversity of Science and Technology 2013

[3] U C Nwaogu C Blawert N Scharnagl W Dietzel and K UKainer ldquoInfluence of inorganic acid pickling on the corrosionresistance of magnesium alloy AZ31 sheetrdquo Corrosion Sciencevol 51 no 11 pp 2544ndash2556 2009

[4] D Talbot Corrosion Science and Technology CRC Press BocaRaton Fla USA 1st edition 1998

[5] L Bammou M Belkhaouda R Salghi et al ldquoCorrosion inhi-bition of steel in sulfuric acidic solution by the ChenopodiumAmbrosioides extractsrdquo Journal of the Association of Arab Uni-versities for Basic and Applied Sciences vol 16 pp 83ndash90 2014

[6] N O Obi-Egbedi I B Obot and S A Umoren ldquoSpondiasmombin L as a green corrosion inhibitor for aluminium insulphuric acid correlation between inhibitive effect and elec-tronic properties of extracts major constituents using densityfunctional theoryrdquo Arabian Journal of Chemistry vol 5 no 3pp 361ndash373 2012

[7] M Hazwan Hussin M Jain Kassim N N Razali N H Dahonand D Nasshorudin ldquoThe effect of Tinospora crispa extracts asa natural mild steel corrosion inhibitor in 1 M HCl solutionrdquoArabian Journal of Chemistry 2011

[8] R S Goncalves D S Azambuja and A M Serpa Lucho ldquoElec-trochemical studies of propargyl alcohol as corrosion inhibitorfor nickel copper and coppernickel (5545) alloyrdquo CorrosionScience vol 44 no 3 pp 467ndash479 2002

[9] E Stupnisek-Lisac A Gazivoda andMMadzarac ldquoEvaluationof non-toxic corrosion inhibitors for copper in sulphuric acidrdquoElectrochimica Acta vol 47 no 26 pp 4189ndash4194 2002

[10] S A Abd El-Maksoud ldquoSome phthalazin derivatives as nontoxic corrosion inhibitors for copper in sulphuric acidrdquo Elec-trochimica Acta vol 49 no 24 pp 4205ndash4212 2004

[11] M H Hussin and M J Kassim ldquoElectrochemical thermody-namic and adsorption studies of (+-) catechin hydrate as naturalmild steel corrosion inhibitor in 1MHClrdquo International Journalof Electrochemical Science vol 6 no 5 pp 1396ndash1414 2011

[12] V S Sastri Green Corrosion Inhibitors Theory and PracticeWiley Yukon Canada 2011

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


[14] L Wang ldquoInhibition of mild steel corrosion in phosphoric acidsolution by triazole derivativesrdquo Corrosion Science vol 48 no3 pp 608ndash616 2006

[15] A Y El-Etre ldquoNatural honey as corrosion inhibitor for metalsand alloys I Copper in neutral aqueous solutionrdquo CorrosionScience vol 40 no 11 pp 1845ndash1850 1998

[16] I Radojcic K Berkovic S Kovac and J Vorkapic-Furac ldquoNat-ural honey and black radish juice as tin corrosion inhibitorsrdquoCorrosion Science vol 50 no 5 pp 1498ndash1504 2008

[17] Y Abboud A Abourriche T Saffaj et al ldquoA novel azo dye 8-quinolinol-5-azoantipyrine as corrosion inhibitor for mild steelin acidicmediardquoDesalination vol 237 no 1-3 pp 175ndash189 2009

[18] A Ostovari S M Hoseinieh M Peikari S R Shadizadeh andS J Hashemi ldquoCorrosion inhibition of mild steel in 1 M HClsolution by henna extract a comparative study of the inhibitionby henna and its constituents (lawsone gallic acid 120572-d-glucoseand tannic acid)rdquoCorrosion Science vol 51 no 9 pp 1935ndash19492009

[19] F Zucchi and I H Omar ldquoPlant extracts as corrosion inhibitorsof mild steel in HCl solutionsrdquo Surface Technology vol 24 no4 pp 391ndash399 1985

[20] S A Umoren I B Obot E E Ebenso and N O Obi-EgbedildquoThe Inhibition of aluminium corrosion in hydrochloric acidsolution by exudate gum from Raphia hookerirdquo Desalinationvol 247 no 1ndash3 pp 561ndash572 2009

[21] A Y El-Etre ldquoInhibition of aluminum corrosion usingOpuntiaextractrdquo Corrosion Science vol 45 no 11 pp 2485ndash2495 2003

[22] E E Oguzie ldquoCorrosion inhibition of aluminium in acidicand alkaline media by Sansevieria trifasciata extractrdquo CorrosionScience vol 49 no 3 pp 1527ndash1539 2007

[23] P B Raja and M G Sethuraman ldquoInhibitive effect of blackpepper extract on the sulphuric acid corrosion of mild steelrdquoMaterials Letters vol 62 no 17-18 pp 2977ndash2979 2008

[24] A Y El-Etre and M Abdallah ldquoNatural honey as corrosioninhibitor for metals and alloys II C-steel in high saline waterrdquoCorrosion Science vol 42 no 4 pp 731ndash738 2000

[25] H Gerengi H Goksu and P Slepski ldquoThe inhibition effect ofmad honey on corrosion of 2007-type aluminium alloy in 35Nacl Solutionrdquo Materials Research vol 17 no 1 pp 255ndash2642014

[26] X L Cheng H Y Ma S H Chen R Yu X Chen and Z MYao ldquoCorrosion of stainless steels in acid solutions with organicsulfur-containing compoundsrdquo Corrosion Science vol 41 no 2pp 321ndash333 1998

[27] R Agrawal and T K G Namboodhiri ldquoThe inhibition of cor-rosion and hydrogen embrittlement of AISI 410 stainless steelrdquoJournal of Applied Electrochemistry vol 22 no 4 pp 383ndash3891992

[28] M Abdallah ldquoRhodanine azosulpha drugs as corrosion inhib-itors for corrosion of 304 stainless steel in hydrochloric acidsolutionrdquo Corrosion Science vol 44 no 4 pp 717ndash728 2002

[29] E E Oguzie ldquoEvaluation of the inhibitive effect of some plantextracts on the acid corrosion of mild steelrdquo Corrosion Sciencevol 50 no 11 pp 2993ndash2998 2008

[30] G Chen M Zhang J Zhao R Zhou Z Meng and J ZhangldquoInvestigation of Ginkgo biloba leave extracts as corrosion andoil field microorganism inhibitorsrdquo Chemistry Central Journalvol 7 article 83 2013

[31] ASTM ldquoPractice for preparing cleaning and evaluating corro-sion test specimensrdquo ASTM G1-72 ASTM International WestConshohocken Pa USA 1990

[32] E Stupnisek-Lisac A L Bozic and I Cafuk ldquoLow-toxicity cop-per corrosion inhibitorsrdquo Corrosion vol 54 no 9 pp 713ndash7201998

[33] M I Awad ldquoEco friendly corrosion inhibitors inhibitive actionof quinine for corrosion of low carbon steel in 1MHClrdquo Journalof Applied Electrochemistry vol 36 no 10 pp 1163ndash1168 2006

[34] LVrsalovic S Gudic andMKliskic ldquoSalvia officinalisL honeyas corrosion inhibitor for CuNiFe in sodium chloride solutionrdquoIndian Journal of Chemical Technology vol 19 pp 96ndash102 2012

[35] F Kandemirli and S Sagdinc ldquoTheoretical study of corrosioninhibition of amides and thiosemicarbazonesrdquo Corrosion Sci-ence vol 49 no 5 pp 2118ndash2130 2007

[36] A M Fekry and M A Ameer ldquoElectrochemical investigationon the corrosion and hydrogen evolution rate of mild steelin sulphuric acid solutionrdquo International Journal of HydrogenEnergy vol 36 no 17 pp 11207ndash11215 2011

[37] M A Quraishi A Singh V K Singh D K Yadav and A KSingh ldquoGreen approach to corrosion inhibition of mild steel inhydrochloric acid and sulphuric acid solutions by the extract ofMurraya koenigii leavesrdquoMaterials Chemistry and Physics vol122 no 1 pp 114ndash122 2010

[38] E E Oguzie C Unaegbu C N Ogukwe B N Okolue and AI Onuchukwu ldquoInhibition of mild steel corrosion in sulphuricacid using indigo dye and synergistic halide additivesrdquoMateri-als Chemistry and Physics vol 84 no 2-3 pp 363ndash368 2004

[39] E E Ebenso N O Eddy and A O Odiongenyi ldquoCorrosioninhibition and adsorption properties of Methocarbamol andmild steel in acidic mediumrdquo Portugaliae Electrochimica Actavol 27 no 1 pp 13ndash22 2009

[40] A K Satapathy G Gunasekaran S C Sahoo K Amit and PV Rodrigues ldquoCorrosion inhibition by Justicia gendarussa plantextract in hydrochloric acid solutionrdquoCorrosion Science vol 51no 12 pp 2848ndash2856 2009

[41] A S Fouda G Y Elewady and M N El-Haddad ldquoCorro-sion inhibition of carbon steel in acidic solution using someazodyesrdquoCanadian Journal on Scientific and Industrial Researchvol 2 no 1 pp 1ndash18 2011

[42] E E Ebenso ldquoSynergistic effect of halide ions on the corrosioninhibition of Aluminium in H

2SO4using 2-acetylphenothia-

zinerdquoMaterials Chemistry and Physics vol 79 no 1 pp 58ndash702003

[43] S A Umoren and I B Obot ldquoPolyvinylpyrollidone and poly-acrylamide as corrosion inhibitors for mild steel in acidicmediumrdquo Surface Review and Letters vol 15 no 3 pp 277ndash2862008

[44] L Larabi O Benali and Y Harek ldquoCorrosion inhibition ofcold rolled steel in 1 M HClO

4solutions by N-naphtyl N1015840-

phenylthioureardquo Materials Letters vol 61 no 14-15 pp 3287ndash3291 2007

[45] X Li S Deng H Fu and T Li ldquoAdsorption and inhibitioneffect of 6-benzylaminopurine on cold rolled steel in 10MHClrdquoElectrochimica Acta vol 54 no 16 pp 4089ndash4098 2009

[46] A R S Priya V S Muralidharam and A Subramania ldquoDevel-opment of novel acidizing inhibitors for carbon steel corrosionin 15 boiling hydrochloric acidrdquo Corrosion Science vol 64 pp541ndash552 2008

[47] A K Maayta and N A F Al-Rawashdeh ldquoInhibition of acidiccorrosion of pure aluminum by some organic compoundsrdquoCorrosion Science vol 46 no 5 pp 1129ndash1140 2004


[48] M H Hussin and M J Kassim ldquoThe corrosion inhibition andadsorption behavior of Uncaria gambir extract on mild steel in1 M HClrdquo Materials Chemistry and Physics vol 125 no 3 pp461ndash468 2011

[49] K Juttner ldquoElectrochemical impedance spectroscopy (EIS) ofcorrosion processes on inhomogeneous surfacesrdquo Electrochim-ica Acta vol 35 no 10 pp 1501ndash1508 1990

[50] T Pajkossy ldquoImpedance of rough capacitive electrodesrdquo Journalof Electroanalytical Chemistry vol 364 no 1-2 pp 111ndash125 1994

[51] B Qian B Hou and M Zheng ldquoThe inhibition effect of tannicacid on mild steel corrosion in seawater wetdry cyclic condi-tionsrdquo Corrosion Science vol 72 pp 1ndash9 2013

[52] H Y Ma S H Chen B S Yin S Y Zhao and X Q LiuldquoImpedance spectroscopic study of corrosion inhibition ofcopper by surfactants in the acidic solutionsrdquoCorrosion Sciencevol 45 no 5 pp 867ndash882 2003

[53] B Scrosati Impedanza Elettrochimica Corso Teorico-PraticoSCI Modena Italy 1987

[54] G Quartarone M Battilana L Bonaldo and T Tortato ldquoInves-tigation of the inhibition effect of indole-3-carboxylic acid onthe copper corrosion in 05 M H

2SO4rdquo Corrosion Science vol

50 no 12 pp 3467ndash3474 2008[55] A Doner R Solmaz M Ozcan and G Kardas ldquoExperimental

and theoretical studies of thiazoles as corrosion inhibitors formild steel in sulphuric acid solutionrdquo Corrosion Science vol 53no 9 pp 2902ndash2913 2011

[56] C H Hsu and F Mansfeld ldquoConcernng the conversion of theconstant phase element parameter Y

0into a capacitancerdquo Cor-

rosion vol 57 no 9 pp 747ndash748 2001[57] P Bommersbach C Alemany-Dumont J-PMillet and B Nor-

mand ldquoHydrodynamic effect on the behaviour of a corrosioninhibitor film characterization by electrochemical impedancespectroscopyrdquo Electrochimica Acta vol 51 no 19 pp 4011ndash40182006

[58] M Abdallah B A AL Jahdaly and O A Al-Malyo ldquoCorrosioninhibition of carbon steel in hydrochloric acid solution usingnon-ionic surfactants derived from phenol compoundsrdquo Inter-national Journal Electrochemistry Science vol 10 pp 2740ndash27542015

[59] S Garai S Garai P Jaisankar J K Singh and A Elango ldquoA com-prehensive study on crude methanolic extract of Artemisia pal-lens (Asteraceae) and its active component as effective corrosioninhibitors of mild steel in acid solutionrdquo Corrosion Science vol60 pp 193ndash204 2012

[60] M Abdallah ldquoCorrosion behaviour of 304 stainless steel insulphuric acid solutions and its inhibition by some substitutedpyrazolonesrdquoMaterials Chemistry and Physics vol 82 no 3 pp786ndash792 2003

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


Honey is a natural result that is processed by bees fromthe nectar of flower or plant parts However the price ofhoney is expensive and it is commonly used as the drugmakes it nonefficient as an inhibitor on an industrial scaleTherefore we use the bee wax propolis (BWP) extract asinhibitor in the present study The BWP is a waste ofhoneycomb and contains a compound similar to honey soit is possible to be used as a corrosion inhibitor The presentstudy is devoted to investigation of the inhibition efficiencyof the BWP extract for corrosion of 304SS in 05MH

2SO4

solution The corrosion measurement was performed by anelectrochemical methodThe influence of temperature on theinhibition efficiency and mechanism of inhibition and theformation of a passive layer will also be discussed

2 Materials and Methods

21 Sample Preparation Extraction and Inhibitor Character-istics The 304SS in the present study had chemical composi-tion (wt) 004 C 052 Si 092 Mn 0030 P 0002S 958 Ni 1815 Cr and bal Fe The 304SS specimenswith 02mm times 1 cm times 1 cm dimension were prepared forthe working electrode (WE) The WE was added to epoxyresin with a geometric exposed surface area measuring 1 cm2and connected to the electrolyte Before the experiment thespecimen surface was polished with emery paper of grades400 to 1200 consecutively

The BWP is used as honeycomb waste that had beensqueezed 3-4 times These wastes were usually in the formof wax and remaining of sticky honey The BWP wasextracted by liquid-liquid method in order to obtain theoptimum conditions The extract of BWP was characterizedby Fourier Transform Infrared Spectroscopy (FTIR) andHigh Performance Liquid Chromatography (HPLC) FTIRanalysis aims to determine the functional groups containedin the BWP extract FTIR spectra showed the characteristicwavenumber of flavonoids which were a carbonyl group(C=O ketone) at 171267 cmminus1 OH at 336748 cmminus1 andaromatic group at 164902 151402 and 146001 cmminus1 Iden-tification of the main compounds in the BWP extract wasfollowed by HPLC analysis The result of HPLC identifica-tion showed that quercetin (2-(34-dihydroxyphenyl)-357-trihydroxy-4H-chromen-4-one) was the greatest compoundin the BWP extract

22 Electrochemical Measurement Standard ASTM (Amer-ican Standard and Testing) G31 was the reference used inthis measurement [31] One batch contained 05M sulfuricacid solution in various concentrations of BWP extractThere were 7 batches with BWP extract composition asfollows 0 1000 2000 3000 4000 5000 and 6000 ppmThe tests were carried out at room temperature (298K) Theoptimum concentration obtained from the measurement ofroom temperature was later tested at temperature variations(298 308 318 and 328K) Electrochemical measurementwas carried out at room temperature using an AutolabPGSTAT128N The optimum concentration of inhibitor wastested at temperature variations (298 308 318 and 328K)Specimens that have been prepared were then assembled into

an electrochemical cell with AgAgCl (3MKCl) as referenceelectrode (RE) and platinum as an auxiliary electrode (AE)and then immersed in a batch for 30 minutes The startingpotential was minus10 V and the scan rate range extended up+10V at Open Circuit Potential (OCP) with voltage scan rateof 0001 Vs Inhibition efficiency is calculated by [7 25 32]

IE =

119868corr minus 119868corr(119894)

119868corrtimes 100 (1)

where 119868corr and 119868corr(119894) are corrosion current density inmedium without and with the addition of inhibitors

TheElectrochemical Impedance Spectroscopy (EIS)mea-surement was conducted in the range frequency from 1000to 1Hz with amplitude of 15mA peak-to-peak AC signalgalvanostatically at the OCP The working electrode wasimmersed in the test solution for 30 minutes to establishconstant signal at open circuit potential Inhibition efficiencyusing EIS method was formulated by [7 33]

IE =

119877ct(119894) minus 119877ct

119877ct(119894)times 100 (2)

where 119877ct dan 119877ct(119894) are the resistance of the charge transfermedium without and with the addition of inhibitors Theimpedance parameters were calculated by fitting the exper-imental result to equivalent circuit using NOVA 17 software

3 Results and Discussion

31 pH Measurement There were no significant changes inpH by the addition of various concentrations of inhibitorTheaverage pH value of the solution without inhibitor was 15with 3 replicationsThe presence of inhibitor (1000 2000 and3000 ppm) in solution gives the average pH value of 148 147and 144 respectively

32Potentiodynamic PolarizationMeasurements Data obtainedfrom polarization are used to analyze the adsorption mecha-nism [10]Thepolarization curves obtainedwere extrapolatedto calculate corrosion parameters such as 119868corr 119864corr 120573119886 and120573119888[19 24] Figures 1(a) and 1(b) show the Tafel plots for 304SS

in 05MH2SO4without and with various concentrations of

inhibitor and the representative of the extrapolation exampleof Tafel plot for 304SS in 05MH

2SO4solution respec-

tively The results of extrapolation of Tafel plots are shown inTable 1

The optimum IE was 9727 which was gained onthe addition of 2000 ppm (Table 1) These results indicatedthat the corrosion rate of 304SS can be inhibited effectivelywith the increase of concentration that reached 2000 ppmIncreasing of IE value is proportional to decreasing ofcurrent density Data obtained from polarization are usedto analyze the adsorption mechanism [24] At concentrationof 2000 ppm the smallest current density was produceddue to the uniform adsorption of inhibitor molecules onmetal surfaces Optimum inhibition efficiency obtained ata concentration of 2000 ppm and decreased with increasingconcentration of inhibitor was suspected physical adsorption









minus04

minus03

minus02

minus01

00

01

E(V

) (A

gA

gCl (3

M K

Cl))

(a)


Experimental anodic



minus040

minus035

minus030

minus025

minus020

minus015


Ecorr

Icorr

E(V

) (A

gA

gCl (3

M K

Cl))

(b)











minus04

minus03

minus02

minus01

00

01


E(V

) (A

gA

gCl (3

M K

Cl))






2) IE ()

0


2000




0 151212000 23393

lnI c

orr

R2 = 0957

R2 = 0987

0ppm2000 ppm

31 32 33 3430

minus14

minus12

minus10

minus8

minus6

minus4



inhibitor addition



119864119886

119877

(

1

119879

) (3)


119886) which is

















Temkin equation is

log 120579

119862

= log119870 minus 119892120579 (4)






∘


∘ (JmolsdotK)

0 mdash 15057 169692000 minus2044 23471 42489

R2 = 0912

minus18

minus16

minus14

minus12

minus10

minus08

minus06

minus04

minus02

00

02 04 06 08 1000120579

log 120579

C



119870 =

1

555


ads119877119879

) (5)




119868corr = (

119877119879

119873ℎ

) exp(Δ119878∘

119877


119877

) (6)



305 310 315 320 325 330 335 340

R2 = 0946

R2 = 0981

0ppm2000 ppm

minus22

minus20

minus18

minus16

minus14

minus12


ln(I

corr

T)





119904) and con-









2 IE ()

0 803 2496 37765 0996 00691 00141 mdash1000 1135 23750 6211 1003 00029 10555 89492000 1186 29084 5995 1001 00020 11640 91423000 1015 26775 5994 1001 00021 09351 90684000 859 25796 6335 1001 00026 09171 90325000 835 24238 6804 1002 00031 08045 89706000 799 19639 6793 1003 00042 09013 8729

W

CPE



Rct

Rs

200 400 600 8000Z998400 (Ω cm2)

0

100

200

300

400

minusZ998400998400

(Ωcm

2)

Z998400 (Ω)

0

8

minusZ998400998400

(Ω)

(a)


10 20 30 40 500Z (Ω cm2)

0

5

10

15

minusZ998400998400

(Ωcm

2)

(b)












O

OOH

HO

OH

OH

OH

(a)

Fe Fe Fe Fe


+ + + +

(b)




2O3and Cr





2O3and Cr

2O3peaked at angle


2O3







o

o b

a

Fe-CHO

lowast

lowast

o Cr2O3

10 20 30 40 50 60 70 80 90 10002120579

lowast Fe2O3








4 Conclusions








Acknowledgments


References














































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials











minus04

minus03

minus02

minus01

00

01

E(V

) (A

gA

gCl (3

M K

Cl))

(a)


Experimental anodic



minus040

minus035

minus030

minus025

minus020

minus015


Ecorr

Icorr

E(V

) (A

gA

gCl (3

M K

Cl))

(b)











minus04

minus03

minus02

minus01

00

01


E(V

) (A

gA

gCl (3

M K

Cl))






2) IE ()

0


2000




0 151212000 23393

lnI c

orr

R2 = 0957

R2 = 0987

0ppm2000 ppm

31 32 33 3430

minus14

minus12

minus10

minus8

minus6

minus4



inhibitor addition



119864119886

119877

(

1

119879

) (3)


119886) which is

















Temkin equation is

log 120579

119862

= log119870 minus 119892120579 (4)






∘


∘ (JmolsdotK)

0 mdash 15057 169692000 minus2044 23471 42489

R2 = 0912

minus18

minus16

minus14

minus12

minus10

minus08

minus06

minus04

minus02

00

02 04 06 08 1000120579

log 120579

C



119870 =

1

555


ads119877119879

) (5)




119868corr = (

119877119879

119873ℎ

) exp(Δ119878∘

119877


119877

) (6)



305 310 315 320 325 330 335 340

R2 = 0946

R2 = 0981

0ppm2000 ppm

minus22

minus20

minus18

minus16

minus14

minus12


ln(I

corr

T)





119904) and con-









2 IE ()

0 803 2496 37765 0996 00691 00141 mdash1000 1135 23750 6211 1003 00029 10555 89492000 1186 29084 5995 1001 00020 11640 91423000 1015 26775 5994 1001 00021 09351 90684000 859 25796 6335 1001 00026 09171 90325000 835 24238 6804 1002 00031 08045 89706000 799 19639 6793 1003 00042 09013 8729

W

CPE



Rct

Rs

200 400 600 8000Z998400 (Ω cm2)

0

100

200

300

400

minusZ998400998400

(Ωcm

2)

Z998400 (Ω)

0

8

minusZ998400998400

(Ω)

(a)


10 20 30 40 500Z (Ω cm2)

0

5

10

15

minusZ998400998400

(Ωcm

2)

(b)












O

OOH

HO

OH

OH

OH

(a)

Fe Fe Fe Fe


+ + + +

(b)




2O3and Cr





2O3and Cr

2O3peaked at angle


2O3







o

o b

a

Fe-CHO

lowast

lowast

o Cr2O3

10 20 30 40 50 60 70 80 90 10002120579

lowast Fe2O3








4 Conclusions








Acknowledgments


References














































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials







2) IE ()

0


2000




0 151212000 23393

lnI c

orr

R2 = 0957

R2 = 0987

0ppm2000 ppm

31 32 33 3430

minus14

minus12

minus10

minus8

minus6

minus4



inhibitor addition



119864119886

119877

(

1

119879

) (3)


119886) which is

















Temkin equation is

log 120579

119862

= log119870 minus 119892120579 (4)






∘


∘ (JmolsdotK)

0 mdash 15057 169692000 minus2044 23471 42489

R2 = 0912

minus18

minus16

minus14

minus12

minus10

minus08

minus06

minus04

minus02

00

02 04 06 08 1000120579

log 120579

C



119870 =

1

555


ads119877119879

) (5)




119868corr = (

119877119879

119873ℎ

) exp(Δ119878∘

119877


119877

) (6)



305 310 315 320 325 330 335 340

R2 = 0946

R2 = 0981

0ppm2000 ppm

minus22

minus20

minus18

minus16

minus14

minus12


ln(I

corr

T)





119904) and con-









2 IE ()

0 803 2496 37765 0996 00691 00141 mdash1000 1135 23750 6211 1003 00029 10555 89492000 1186 29084 5995 1001 00020 11640 91423000 1015 26775 5994 1001 00021 09351 90684000 859 25796 6335 1001 00026 09171 90325000 835 24238 6804 1002 00031 08045 89706000 799 19639 6793 1003 00042 09013 8729

W

CPE



Rct

Rs

200 400 600 8000Z998400 (Ω cm2)

0

100

200

300

400

minusZ998400998400

(Ωcm

2)

Z998400 (Ω)

0

8

minusZ998400998400

(Ω)

(a)


10 20 30 40 500Z (Ω cm2)

0

5

10

15

minusZ998400998400

(Ωcm

2)

(b)












O

OOH

HO

OH

OH

OH

(a)

Fe Fe Fe Fe


+ + + +

(b)




2O3and Cr





2O3and Cr

2O3peaked at angle


2O3







o

o b

a

Fe-CHO

lowast

lowast

o Cr2O3

10 20 30 40 50 60 70 80 90 10002120579

lowast Fe2O3








4 Conclusions








Acknowledgments


References














































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials







∘


∘ (JmolsdotK)

0 mdash 15057 169692000 minus2044 23471 42489

R2 = 0912

minus18

minus16

minus14

minus12

minus10

minus08

minus06

minus04

minus02

00

02 04 06 08 1000120579

log 120579

C



119870 =

1

555


ads119877119879

) (5)




119868corr = (

119877119879

119873ℎ

) exp(Δ119878∘

119877


119877

) (6)



305 310 315 320 325 330 335 340

R2 = 0946

R2 = 0981

0ppm2000 ppm

minus22

minus20

minus18

minus16

minus14

minus12


ln(I

corr

T)





119904) and con-









2 IE ()

0 803 2496 37765 0996 00691 00141 mdash1000 1135 23750 6211 1003 00029 10555 89492000 1186 29084 5995 1001 00020 11640 91423000 1015 26775 5994 1001 00021 09351 90684000 859 25796 6335 1001 00026 09171 90325000 835 24238 6804 1002 00031 08045 89706000 799 19639 6793 1003 00042 09013 8729

W

CPE



Rct

Rs

200 400 600 8000Z998400 (Ω cm2)

0

100

200

300

400

minusZ998400998400

(Ωcm

2)

Z998400 (Ω)

0

8

minusZ998400998400

(Ω)

(a)


10 20 30 40 500Z (Ω cm2)

0

5

10

15

minusZ998400998400

(Ωcm

2)

(b)












O

OOH

HO

OH

OH

OH

(a)

Fe Fe Fe Fe


+ + + +

(b)




2O3and Cr





2O3and Cr

2O3peaked at angle


2O3







o

o b

a

Fe-CHO

lowast

lowast

o Cr2O3

10 20 30 40 50 60 70 80 90 10002120579

lowast Fe2O3








4 Conclusions








Acknowledgments


References














































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials







2 IE ()

0 803 2496 37765 0996 00691 00141 mdash1000 1135 23750 6211 1003 00029 10555 89492000 1186 29084 5995 1001 00020 11640 91423000 1015 26775 5994 1001 00021 09351 90684000 859 25796 6335 1001 00026 09171 90325000 835 24238 6804 1002 00031 08045 89706000 799 19639 6793 1003 00042 09013 8729

W

CPE



Rct

Rs

200 400 600 8000Z998400 (Ω cm2)

0

100

200

300

400

minusZ998400998400

(Ωcm

2)

Z998400 (Ω)

0

8

minusZ998400998400

(Ω)

(a)


10 20 30 40 500Z (Ω cm2)

0

5

10

15

minusZ998400998400

(Ωcm

2)

(b)












O

OOH

HO

OH

OH

OH

(a)

Fe Fe Fe Fe


+ + + +

(b)




2O3and Cr





2O3and Cr

2O3peaked at angle


2O3







o

o b

a

Fe-CHO

lowast

lowast

o Cr2O3

10 20 30 40 50 60 70 80 90 10002120579

lowast Fe2O3








4 Conclusions








Acknowledgments


References














































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




O

OOH

HO

OH

OH

OH

(a)

Fe Fe Fe Fe


+ + + +

(b)




2O3and Cr





2O3and Cr

2O3peaked at angle


2O3







o

o b

a

Fe-CHO

lowast

lowast

o Cr2O3

10 20 30 40 50 60 70 80 90 10002120579

lowast Fe2O3








4 Conclusions








Acknowledgments


References














































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials







4 Conclusions








Acknowledgments


References














































































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



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