research article synergistic effect of iodide ion and 4 ...also, the oxonium ion formed in the...

Hindawi Publishing CorporationISRN CorrosionVolume 2013 Article ID 184787 6 pageshttpdxdoiorg1011552013184787

Research ArticleSynergistic Effect of Iodide Ion and 4-Hydroxy Coumarin onthe Corrosion Inhibition of Mild Steel in Hydrochloric Acid

Shyamala R Krishnamurthy and Meenakshi H N Parameswaran

Department of Chemistry Avinashilingam Institute for Home Science and Higher Education for Women CoimbatoreTamil Nadu 641043 India

Correspondence should be addressed to Meenakshi H N Parameswaran meenaparam75gmailcom

Received 21 May 2013 Accepted 10 June 2013

Academic Editors C Gervasi and H Miao

Copyright copy 2013 S R Krishnamurthy and M H N Parameswaran This is an open access article distributed under the CreativeCommons Attribution License which permits unrestricted use distribution and reproduction in any medium provided theoriginal work is properly cited

No discussion of the use of inhibitors in acid solution is complete without mentioning the phenomenon of synergism Synergismalso operates in corrosion protection where an enhanced inhibition may be related to interaction between inhibitor compoundsThis effect has been observed since the earlier days of inhibitor technology and continues to be a potent tool in the development ofacid inhibitors for specialized uses Hence in this paper the corrosion inhibition behavior of mild steel (MS) in 1M hydrochloricacid in the presence of 4-hydroxy coumarin (4HC) and potassium iodide (KI) has been investigated using the mass loss methodand electrochemical techniques The inhibitive performance of 4HC is considerably enhanced by the addition of 1 times 10minus3 KIThe addition of KI to different concentrations of 4HC has intensified its efficiency through considerable reduction in the mass losscorrosion current density 119868corr double layer capacitance119862dl and increase in charge transfer resistance119877ctThe calculated synergismparameter ldquo119878rdquo is greater than unity thereby proving the fact that the improvement in inhibition efficiency of 4HC generated by theaddition of KI is due to synergism

1 Introduction

Synergism literallymeans joint action of different processes inproducing an effect greater than the sum of their individualeffects This effect has been observed since the earlier daysof inhibitor technology and continues to be a potent tool inthe development of acid inhibitors for specialized uses Infact the inhibitive nature of most of the extracts of commonplants used to combat corrosion of metals is known to befortified through synergism of many organic constituentspresent In modern practice inhibitors are rarely used in theform of single compounds A formulation of two or moreorganic compounds andor inorganic compounds is usuallyemployed The synergistic action of anions on the inhibitionof mild steel corrosion in acid solution containing organiccompound has been reported by several authors [1ndash4] Inview of this the enhancement of protection efficiency of thechosen coumarin inhibitor by iodide ions against mild steelcorrosion in 1M hydrochloric acid has been studied

2 Experimental Parts

21 Synthesis of 4-Hydroxy Coumarin The microwaveassisted synthesis of 4-hydroxy coumarin (4HC) was carriedout in an ordinary domestic microwave oven by the vonPechmann reaction of phenol malonic acid fused ZnCl

2

and a few drops of POCl

3

for 60ndash40 seconds at 450W Themechanism of the reaction is shown in Scheme 1 [5]

22 Preparation of the Sample MS specimens of area 5 times1 cm2 having composition C = 0049 Mn = 0346 Si =0026 P = 0038 S = 0020 Cr = 0050 Mo = 0019Ni = 0019 and the reminder Fe were used for the entirestudy MS specimens with an exposed area of 1 cm2 were usedfor polarization and impedance studies The specimens weredegreased cleanedwith fine quality emery sheet washedwithdistilled water and stored in desiccators before they are usedfor the investigation

2 ISRN Corrosion

Table 1 IE in presence of 10minus3 M KI and synergism parameter

[Inh] 10minus3 M KI 0001 0003 0005 0007 0009 001

1 hI1 I2 01778 00500 01537 02583 03718 04329 055861198681015840

1+2

mdash 03472 04966 06200 06687 07122 07920119878 mdash 11970 13820 16650 15590 16200 17450

3 hI1 I2 00915 00996 02727 03402 04373 04460 056781198681015840

1+2

mdash 02610 04537 04959 05820 06474 07537119878 mdash 11070 12100 11890 12230 14270 15940

6 hI1 I2 02799 02665 03949 04164 04897 05742 062521198681015840

1+2

mdash 05339 05814 06189 06699 07307 07589119878 mdash 11330 10410 11030 11130 11390 11200

12 hI1 I2 01139 01483 03011 03731 04592 04611 047591198681015840

1+2

mdash 01907 03495 04346 04795 05619 06764119878 mdash 09330 09520 09830 09210 10900 14350

COOH

COOH

O O

OH

OHCH2+

ZnCl2POCl3MW

Scheme 1 Synthesis of 4-hydroxy coumarin

23 Weight Loss Method MS specimens were accuratelyweighed and fully immersed in 100 mL of 1M HCl in theabsence and presence of the inhibitors of various concentra-tions removed after a particular period of immersion dippedin sodium bicarbonate solution (for neutralizing the remain-ing acid on the specimen) washed dried and reweighedThe loss in weight was determined in triplicate and theresults were averaged The experiment was performed forinvestigating the parameters such as inhibitor concentration(0001 to 001M) immersion (1 h 3 h 6 h and 12 h) andsynergism (presence of 10minus3M KI) The rates of corrosionand inhibition efficiency were calculated by the followingformulae [6]

Corrosion rate (mpy)

=534 times weight loss in mgs

Density times Area in square inch times Time in hrs

IE = (Corrosion rate without inhibitorminus Corrosion rate with inhibitor)

times (Corrosion rate without inhibitor)minus1 times 100(1)

24 Polarization Technique A frequency response analyzer1280B (Solartron) and an IBM personal computer were usedfor the polarization studyThe cell for the polarization studieswas a glass beaker containing the aerated unstirred testsolution with a platinum electrode as the counter electrode asaturated calomel electrode as the reference electrode and themild steel electrode as the working electrode 100 mL of 1MHCl with and without different concentrations of inhibitorswas taken in an electrochemical cell The polished electrodewas then introduced The electrode was placed at minus1mV

cathodic to its open circuit potential Thus the potential wasscanned at minus01mVsec towards the anodic direction in Tafelextrapolation Applied potential versus current was plottedand on extrapolation of linear portion to the corrosionpotential gives the corrosion current In anodic and cathodicplots the slope of the linear portion gave Tafel constants ldquo119887

119886

rdquoand ldquo119887

119888

rdquo respectively Inhibition efficiency was calculated bythe following formula [7 8]

IE = (Corrosion current without inhibitor

minus Corrosion current with inhibitor)

times (Corrosion current with inhibitor)minus1 times 100

(2)

25 AC Impedance Method The electrochemical impedancemeasurements were carried out using mild steel in acidmedium with and without an inhibitor using the samepotentiostat A plot of real part of impedance (1199111015840) andimaginary part of impedance (11991110158401015840) was made and from thisthe charge transfer resistance (119877ct) double layer capacitance(119862dl) and inhibition efficiency were calculated using ZViewsoftware The inhibitor efficiency was obtained from theelectrochemical parameters as below [9ndash11]

IE =Rp(119894)

minus RpRp(119894)

times 100

IE =Rct(119894)

minus RctRct(119894)

times 100

(3)

where Rp and Rct are Polarization resistance and chargetransfer resistance in the absence of the inhibitor respectivelyand Rp

(119894)

and Rct(119894)

are Polarization resistance and chargetransfer resistance in the presence of the inhibitor respec-tively

3 Results and Discussion

31 Mass Loss Method The values of IE for the specificconcentrations of 4HCand in combinationwith 10minus3MKI aregiven in Table 1 The interesting feature of the investigation is

ISRN Corrosion 3

Table 2 Electrode kinetic parameters for corrosion of mild steel in 1M HCl with various concentrations of 4-hydroxy coumarin in thepresence and absence of 10minus3 M KI

[Inh] M [KI] M minus119864corr mV 119868corr mAcm2119887119886

mVdec 119887119888

mVdec IE 119878

Blank mdash 506 1112 206 166 mdash mdashmdash 10minus3 503 839 199 162 2455 mdash0001 mdash 509 1004 230 180 973 1126mdash 10minus3 496 672 152 130 39520007 mdash 483 654 199 143 4119 1197mdash 10minus3 516 412 149 152 62940009 mdash 492 640 180 143 4317 1167mdash 10minus3 496 408 163 129 63270010 mdash 495 441 174 154 6081 1128mdash 10minus3 509 296 126 111 7339

minus1

minus075

minus05

minus025

0

E (V

)

10minus5

10minus4

10minus3

10minus2

10minus1

100

I (Ampscm2)

Blank + KI corBlank 1 M HCl cor

0001 M cor

0007 M cor001 M cor

Figure 1 Tafel plot for corrosion ofmild steel in 1MHCl containingdifferent concentrations of 4-hydroxy coumarin

that the compound gave better inhibitive performance in thepresence of 1 times 10minus3M potassium iodide This enhancementin the IE on the addition of KI occurs due to synergistic effect

The interaction of inhibitor molecules can be describedby the introduction of synergism parameter 119878 was evaluatedusing the relationship given by Aramaki and Hackerman andreported elsewhere [12 13]

119878 =1 minus 11986812

1 minus 1198681+2

(4)

11986812

is the calculated inhibition effect supposing additivity(no interaction between the inhibitor compounds exists) 119868

12

can be expressed as 11986812

= 1198681

+ 1198682

minus (1198681

1198682

) 1198681

is the measuredinhibition effect of 1times10minus3MKI 119868

2

is themeasured inhibitioneffect of 4HC and 119868

(1+2)

is the measured inhibition effect forthe combination of 4HC and 1times10minus3MKIThe values of ldquo119878rdquothe synergism parameter for different concentrations of 4HC

0001 M cor0007 M cor001 M cor

10minus4

10minus3

10minus2

10minus1

100

I (Ampscm2)

minus1

minus075

minus05

minus025

E (V

)

Figure 2 Tafel plot for corrosion ofmild steel in 1MHCl containingdifferent concentrations of 4-hydroxy coumarin in the presence of10minus3 KI

in 1M HCl in combination with iodide ions are higher thanunity suggesting the synergistic effect

32 Polarization Measurements Figures 1 and 2 representthe anodic and cathodic polarization curves of mild steel in1MHCl devoid of and containing different concentrations of4HCand in the presence of 1times10minus3MKIThe electrochemicalparameters of mild steel corrosion in free and inhibited 1MHCl solutions were given in Table 2 It can be seen from thetable that as the concentration of the coumarins is increasedthere is little change in the corrosion potential Moreover thecorrosion current (119868corr) decreases markedly in the presenceof the inhibitor and themagnitude of such an effect increaseswith increasing inhibitor concentrationThese results showedthe inhibitive action of the coumarin to corrosion of mildsteel in the acidic medium Also it can be seen from the tablethat the addition of 1 times 10minus3M KI further reduces the 119868corrvalues exhibiting synergism

4 ISRN Corrosion

00 10 20 30 40

Blank + KIz

minus10

minus20

minus30

Z998400

Z998400998400

Blank 1M HClz

0001Mz

0007Mz001Mz

Figure 3 Complex-plane impedance of mild steel in 1M HCl withdifferent concentrations of 4-hydroxy coumarin

The values of inhibition efficiency increase with theincrease in coumarin concentrations reaching themaximumvalues of 6081 at 001M The addition of KI has enhancedthe percentage efficiency which could be attributed to syner-gistic effect The presence of synergism has been establishedby calculating the synergism parameter ldquo119878rdquo which is recordedin Table 2 Almost all values are greater than unity therebyproving the fact that the improvement in inhibition efficiencyof 4HC generated by the addition of KI is due to synergism

33 Electrochemical Impedance Spectroscopy Figure 3 repre-sents the Nyquist plot obtained for MS in 1MHCl in absenceand presence of various concentrations of the inhibitorImpedance responses of acid solution containing variousconcentrations of the inhibitor in combination with 1 times10minus3MKI solution are depicted in Figure 4The inhibition efficiency was calculated from 119862dl values

applying the following formula

IE = 1 minus [119862dl(119894)

119862dl] times 100 (5)

where 119862dl(119894) is the double layer capacitance value in the pres-ence of the inhibitor and 119862dl is the double layer capacitancevalue in the absence of the inhibitor

The calculated inhibition efficiencies from the valuesof 119862dl obtained from the impedance spectra was given inTable 3 The protecting capacity of 4HC was found to beincreasing with the increase in its concentration Due tosynergism the addition of KI has caused an enhancement inthe protecting ability

In order to correlate impedance and polarization meth-ods 119868corr values were obtained from the Nyquist plots for

0 10 20 30 40 50 60

0001 Mz 0007 Mz 001 Mz

0

minus10

minus20

minus30

minus40

minus50

Z998400998400

Z998400

Figure 4 Complex-plane impedance of mild steel in 1M HCl withdifferent concentrations of 4-hydroxy coumarin in the presence of10minus3MKI

different concentration of the inhibitor in the absence andpresence of 10minus3MKI using the Stern-Geary equation [14]

119868corr =119887119886

times 119887119888

23 (119887119886

+ 119887119888

) 119877ct (6)

The obtained 119868corr and IE values with different concentra-tions of 4HC in the absence and presence of KI are given inTable 4

The enhanced inhibition efficiency can be explained asdue to joint adsorption of iodide ions and inhibitor cationsor molecules When irreversible chemisorption of iodideions takes place and stable metal-iodide covalent bonds areformed the iodide ions enter the metallic part of the doublelayer and the charge of the metal surface which in turnattracts the positively charged inhibitor cations rendering theadsorption more effective

Synergism can also happen according to a molecularmechanism The coumarin cations created as a result ofprotonation exist only in the solution On entering the doublelayer they become discharged The molecules produced areadsorbed at the expense of the unpaired electrons of theheteroatom

4 Conclusions

(1) The inhibition efficiency of the inhibitor increasedwith the increase in its concentration at all immersiontimes

ISRN Corrosion 5

Table 3 Impedance parameters for corrosion of mild steel in 1MHCl for different concentration of 4-hydroxy coumarin in the presence andabsence of 10minus3 M KI

[Inh] M [KI] M 119877ct Ω cm2 IE 119862dl 120583Fcm

2 IEBlank mdash 1565 mdash 425 mdashmdash 10minus3 2200 2886 328 22820001 mdash 1803 1320 385 941mdash 10minus3 2304 3207 344 19060003 mdash 1971 2060 376 1153mdash 10minus3 2396 3468 318 25180007 mdash 3012 4804 280 3412mdash 10minus3 4194 6268 124 70820009 mdash 3144 5022 278 3459mdash 10minus3 4431 6468 121 71530010 mdash 3748 5824 149 6494mdash 10minus3 5158 6960 111 7388

Table 4 Values of 119868corr and IE for corrosion of mild steel in 1MHClwith different concentrations of 4-hydroxy coumarin in absenceand presence of 10minus3 M KI obtained by Stern-Geary equation

[Inh] M [KI] M 119868corr mAcm2 IEBlank mdash 255 mdashmdash 10minus3 176 30980001 mdash 243 471mdash 10minus3 101 60390007 mdash 120 5294mdash 10minus3 078 69410009 mdash 115 5490mdash 10minus3 071 72160010 mdash 095 6275mdash 10minus3 050 8039

(2) The presence of 10minus3M KI boosted the inhibitiveefficiency of the coumarin

(3) The synergism parameter 119878 obtained by the Aramakiand Hackerman equation was found to be greaterthan unityThis suggests that the enhanced inhibitionefficiency caused by the addition of iodide ion is dueonly to synergistic effect

(4) The concentration dependence of the inhibition effi-ciency calculated from electrochemical studies hasthe same trend as that obtained from weight lossmeasurements

(5) 4-Hydroxy coumarin covers both the anodic andcathodic regions through general adsorption Theadsorption occurs through the activated nonbondedelectrons on the lactone oxygen and the 120587 electronsof the aromatic rings can adsorb onto the metalsurface Further the minusOH group at the 4th positionshifts the electron flow towards the pyranone ring dueto +M effect Also the oxonium ion formed in theacidic solution can be adsorbed on the metal surfacethrough columbic interaction

Acknowledgment

The authors would like to thank the authorities of theAvinashilingam Institute for Home Science and Higher Edu-cation for Women for providing necessary facilities to carryout this study

References

[1] K S Sudhish K S Ashish C M Lutendo M K Mwadhamand E E Eno ldquoInhibitive effect of azorubine dye on thecorrosion of mild steel in hydrochloric acid medium and syner-gistic iodide additiverdquo International Journal of ElectrochemicalScience vol 7 pp 5057ndash5068 2012

[2] M Ajmal A S Mideen and M A Quraishi ldquo2-hydrazino-6-methyl-benzothiazole as an effective inhibitor for the corrosionof mild steel in acidic solutionsrdquo Corrosion Science vol 36 no1 pp 79ndash84 1994

[3] A Y Musa A B Mohamad A A H Kadhum M S Takriffand L T Tien ldquoSynergistic effect of potassium iodide withphthalazone on the corrosion inhibition of mild steel in 10MHClrdquo Corrosion Science vol 53 no 11 pp 3672ndash3677 2011

[4] E E Ebenso A Hailemichael S A Umoren and I BObot ldquoInhibition of mild steel corrosion in sulphuric acidusing Alizarin yellow GG dye and synergistic iodide additiverdquoInternational Journal of Electrochemical Science vol 3 pp 1325ndash1339 2008

[5] V K Ahluwalia and R Aggarwal Comprehensive PracticalOrganic Chemistry Preparation and Quantitative Analysis Uni-versities Press Hyderabad India 2000

[6] R SarathaM SaranyaDeviHNMeenakshi andR ShyamalaldquoEnhanced corrosion resistance of Tecoma stans extract onmildsteel in 0 5M H

2

SO4

solutionrdquo International Journal of CurrentResearch vol 2 pp 92ndash96 2011

[7] H Baeza M Guzman P Ortega and L Vera ldquoCorrosioninhibition of copper in 05 M hydrochloric acid by 134-thiadiazole-25-dithiolrdquo Journal of the Chilean Chemical Societyvol 48 no 3 pp 23ndash26 2003

[8] W AW E Amira A A Rahim H Osman K Awang and P BRaja ldquoCorrosion inhibition of mild steel in 1 MHCl solution byXylopia ferruginea leaves from different extract and partitionsrdquo

6 ISRN Corrosion

International Journal of Electrochemical Science vol 6 no 7 pp2998ndash3016 2011

[9] S Ambrish S Ashish Kumar and M A Quraishi ldquoDapsone anovel corrosion inhibitor formild steel in acidmediardquoTheOpenElectrochemistry Journal vol 2 pp 43ndash51 2010

[10] M Z A Rafiquee S Khan N Saxena and M A QuraishildquoInfluence of some thiadiazole derivatives on corrosion inhibi-tion of mild steel in formic and acetic acid mediardquo PortugaliaeElectrochimica Acta vol 25 pp 419ndash434 2007

[11] J-Q XueMWu J-X Li C-B Tang andC-X Yin ldquoInhibitionbehavior of a novel acidification inhibitor for steels at hightemperaturerdquo Materials Science Forum vol 686 pp 574ndash5782011

[12] S A Umoren and E E Ebenso ldquoThe synergistic effect ofpolyacrylamide and iodide ions on the corrosion inhibition ofmild steel in H

2

SO4

rdquoMaterials Chemistry and Physics vol 106no 2-3 pp 387ndash393 2007

[13] S A Umoren E E Ebenso P C Okafor U J Ekpe andO Ogbobe ldquoEffect of halide ions on the corrosion inhibitionof aluminium in alkaline medium using polyvinyl alcoholrdquoJournal of Applied Polymer Science vol 103 no 5 pp 2810ndash28162007

[14] L Larabi Y Harek M Traisnel and A Mansri ldquoSynergisticinfluence of poly(4-vinylpyridine) and potassium iodide oninhibition of corrosion of mild steel in 1M HClrdquo Journal ofApplied Electrochemistry vol 34 no 8 pp 833ndash839 2004

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Smart Materials Research



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materials


Journal ofNanomaterials

2 ISRN Corrosion

Table 1 IE in presence of 10minus3 M KI and synergism parameter

[Inh] 10minus3 M KI 0001 0003 0005 0007 0009 001

1 hI1 I2 01778 00500 01537 02583 03718 04329 055861198681015840

1+2

mdash 03472 04966 06200 06687 07122 07920119878 mdash 11970 13820 16650 15590 16200 17450

3 hI1 I2 00915 00996 02727 03402 04373 04460 056781198681015840

1+2

mdash 02610 04537 04959 05820 06474 07537119878 mdash 11070 12100 11890 12230 14270 15940

6 hI1 I2 02799 02665 03949 04164 04897 05742 062521198681015840

1+2

mdash 05339 05814 06189 06699 07307 07589119878 mdash 11330 10410 11030 11130 11390 11200

12 hI1 I2 01139 01483 03011 03731 04592 04611 047591198681015840

1+2

mdash 01907 03495 04346 04795 05619 06764119878 mdash 09330 09520 09830 09210 10900 14350

COOH

COOH

O O

OH

OHCH2+

ZnCl2POCl3MW

Scheme 1 Synthesis of 4-hydroxy coumarin

23 Weight Loss Method MS specimens were accuratelyweighed and fully immersed in 100 mL of 1M HCl in theabsence and presence of the inhibitors of various concentra-tions removed after a particular period of immersion dippedin sodium bicarbonate solution (for neutralizing the remain-ing acid on the specimen) washed dried and reweighedThe loss in weight was determined in triplicate and theresults were averaged The experiment was performed forinvestigating the parameters such as inhibitor concentration(0001 to 001M) immersion (1 h 3 h 6 h and 12 h) andsynergism (presence of 10minus3M KI) The rates of corrosionand inhibition efficiency were calculated by the followingformulae [6]

Corrosion rate (mpy)

=534 times weight loss in mgs

Density times Area in square inch times Time in hrs

IE = (Corrosion rate without inhibitorminus Corrosion rate with inhibitor)

times (Corrosion rate without inhibitor)minus1 times 100(1)

24 Polarization Technique A frequency response analyzer1280B (Solartron) and an IBM personal computer were usedfor the polarization studyThe cell for the polarization studieswas a glass beaker containing the aerated unstirred testsolution with a platinum electrode as the counter electrode asaturated calomel electrode as the reference electrode and themild steel electrode as the working electrode 100 mL of 1MHCl with and without different concentrations of inhibitorswas taken in an electrochemical cell The polished electrodewas then introduced The electrode was placed at minus1mV

cathodic to its open circuit potential Thus the potential wasscanned at minus01mVsec towards the anodic direction in Tafelextrapolation Applied potential versus current was plottedand on extrapolation of linear portion to the corrosionpotential gives the corrosion current In anodic and cathodicplots the slope of the linear portion gave Tafel constants ldquo119887

119886

rdquoand ldquo119887

119888

rdquo respectively Inhibition efficiency was calculated bythe following formula [7 8]

IE = (Corrosion current without inhibitor

minus Corrosion current with inhibitor)

times (Corrosion current with inhibitor)minus1 times 100

(2)

25 AC Impedance Method The electrochemical impedancemeasurements were carried out using mild steel in acidmedium with and without an inhibitor using the samepotentiostat A plot of real part of impedance (1199111015840) andimaginary part of impedance (11991110158401015840) was made and from thisthe charge transfer resistance (119877ct) double layer capacitance(119862dl) and inhibition efficiency were calculated using ZViewsoftware The inhibitor efficiency was obtained from theelectrochemical parameters as below [9ndash11]

IE =Rp(119894)

minus RpRp(119894)

times 100

IE =Rct(119894)

minus RctRct(119894)

times 100

(3)

where Rp and Rct are Polarization resistance and chargetransfer resistance in the absence of the inhibitor respectivelyand Rp

(119894)

and Rct(119894)

are Polarization resistance and chargetransfer resistance in the presence of the inhibitor respec-tively

3 Results and Discussion

31 Mass Loss Method The values of IE for the specificconcentrations of 4HCand in combinationwith 10minus3MKI aregiven in Table 1 The interesting feature of the investigation is

ISRN Corrosion 3



mVdec 119887119888

mVdec IE 119878


minus1

minus075

minus05

minus025

0

E (V

)

10minus5

10minus4

10minus3

10minus2

10minus1

100

I (Ampscm2)


0001 M cor

0007 M cor001 M cor




119878 =1 minus 11986812

1 minus 1198681+2

(4)

11986812


12


= 1198681

+ 1198682

minus (1198681

1198682

) 1198681


2


(1+2)



10minus4

10minus3

10minus2

10minus1

100

I (Ampscm2)

minus1

minus075

minus05

minus025

E (V

)




4 ISRN Corrosion

00 10 20 30 40

Blank + KIz

minus10

minus20

minus30

Z998400

Z998400998400

Blank 1M HClz

0001Mz

0007Mz001Mz





IE = 1 minus [119862dl(119894)

119862dl] times 100 (5)




0 10 20 30 40 50 60

0001 Mz 0007 Mz 001 Mz

0

minus10

minus20

minus30

minus40

minus50

Z998400998400

Z998400



119868corr =119887119886

times 119887119888

23 (119887119886

+ 119887119888

) 119877ct (6)




4 Conclusions


ISRN Corrosion 5










Acknowledgment


References







2

SO4




6 ISRN Corrosion






2

SO4











CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



ISRN Corrosion 3



mVdec 119887119888

mVdec IE 119878


minus1

minus075

minus05

minus025

0

E (V

)

10minus5

10minus4

10minus3

10minus2

10minus1

100

I (Ampscm2)


0001 M cor

0007 M cor001 M cor




119878 =1 minus 11986812

1 minus 1198681+2

(4)

11986812


12


= 1198681

+ 1198682

minus (1198681

1198682

) 1198681


2


(1+2)



10minus4

10minus3

10minus2

10minus1

100

I (Ampscm2)

minus1

minus075

minus05

minus025

E (V

)




4 ISRN Corrosion

00 10 20 30 40

Blank + KIz

minus10

minus20

minus30

Z998400

Z998400998400

Blank 1M HClz

0001Mz

0007Mz001Mz





IE = 1 minus [119862dl(119894)

119862dl] times 100 (5)




0 10 20 30 40 50 60

0001 Mz 0007 Mz 001 Mz

0

minus10

minus20

minus30

minus40

minus50

Z998400998400

Z998400



119868corr =119887119886

times 119887119888

23 (119887119886

+ 119887119888

) 119877ct (6)




4 Conclusions


ISRN Corrosion 5










Acknowledgment


References







2

SO4




6 ISRN Corrosion






2

SO4











CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



4 ISRN Corrosion

00 10 20 30 40

Blank + KIz

minus10

minus20

minus30

Z998400

Z998400998400

Blank 1M HClz

0001Mz

0007Mz001Mz





IE = 1 minus [119862dl(119894)

119862dl] times 100 (5)




0 10 20 30 40 50 60

0001 Mz 0007 Mz 001 Mz

0

minus10

minus20

minus30

minus40

minus50

Z998400998400

Z998400



119868corr =119887119886

times 119887119888

23 (119887119886

+ 119887119888

) 119877ct (6)




4 Conclusions


ISRN Corrosion 5










Acknowledgment


References







2

SO4




6 ISRN Corrosion






2

SO4











CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



ISRN Corrosion 5










Acknowledgment


References







2

SO4




6 ISRN Corrosion






2

SO4











CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



6 ISRN Corrosion






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 synergistic effect of iodide ion and 4 ...also, the oxonium ion formed in the...

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