Research Article Evaluation of Corrosion ... - Hindawi

Research ArticleEvaluation of Corrosion Inhibition of Mild Steel in 1 MHydrochloric Acid Solution by Mollugo cerviana

P Arockiasamy1 X Queen Rosary Sheela2 G Thenmozhi1 M Franco3

J Wilson Sahayaraj4 and R Jaya Santhi1

1 PG amp Research Department of Chemistry Auxilium College Vellore 632 006 India2 PG amp Research Department of Chemistry St Josephrsquos College Trichy 620 002 India3 School of Planning Architecture and Civil Engineering Queenrsquos University Belfast Belfast BT7 1NN UK4Department of Chemistry Jeppiaar Engineering College Chennai 600119 India

Correspondence should be addressed to R Jaya Santhi shanthijaya02gmailcom

Received 28 January 2014 Revised 19 June 2014 Accepted 8 July 2014 Published 21 July 2014

Academic Editor Sebastian Feliu

Copyright copy 2014 P Arockiasamy et alThis is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

The inhibiting effect of methanolic extract of Mollugo cerviana plant on the corrosion of mild steel in 1M HCl solution hasbeen investigated by different techniques like potentiodynamic polarization electrochemical impedance spectroscopy and weightloss methods for five different concentrations of plant extract ranging from 25 to 1000mgL The results indicated that thecorrosion inhibition efficiency increased on increasing plant extract concentration till 500mgL anddecreased on further increasingconcentrationThe extract was a mixed type inhibitor with the optimum inhibition concentration of 500mgL in potentiodynamicpolarizationThe adsorption of the plant extract on themild steel surface was found to obey Langmuir adsorption isotherm Surfaceanalysis was also carried out to find out the surface morphology of the mild steel in the presence and in the absence of the inhibitorto find out its efficiency The obtained results showed that theMollugo cerviana extract acts as a good inhibitor for the corrosion ofmild steel in 1M HCl solution

1 Introduction

Corrosion inhibitors have been widely studied in manyindustries to reduce the corrosion rate of metal surfacesin contact with aggressive medium [1ndash3] Acidic solutionsare commonly used in various industries and applicationsinclude acid pickling industrial cleaning acid rescaling oil-well acidification and petrochemical processes [4] Amongthe acid solutions hydrochloric acid is one of themost widelyused in the pickling processes of metals

Use of inhibitors is one of the most practical methodsfor protection against corrosion especially in acid solutionsto prevent metal dissolution and acid consumption [5] Mildsteel in acid solution is widely used in various industrialprocesses and corrosion of mild steel known to occur inthis environment One of the effective methods to preventcorrosion is the use of organic inhibitors [6] A great numberof scientific studies have been devoted to the subject ofcorrosion inhibitors for mild steel in acidic media [2 7ndash14]

Plant extracts are viewed as environmentally friendly andecologically acceptable inhibitors Plant products are low-cost readily available and renewable sources of materialsThe extracts from their leaves barks seeds fruits androots comprise of mixtures of organic compounds containingnitrogen sulphur and oxygen atoms and some [15ndash20] havebeen reported to function as effective inhibitors of metalcorrosion in different aggressive environments Generally theinhibitive effect of plant extract is attributed to the adsorptionof organic substances on the metal surface blocking activesites or even forming a protective barrier

In recent years natural compounds such as herbal plantsare employed as inhibitors in order to develop new cleaningchemicals for green environment Several studies have beenreported in the use of natural products as corrosion inhibitorsin different media [21ndash30]

M cerviana (L) Ser (Molluginaceae) has been widelyused as a pot herb enhances eyesight reduces body odouracts as a good antiseptic and is used in the treatment of

Hindawi Publishing CorporationInternational Journal of CorrosionVolume 2014 Article ID 679192 7 pageshttpdxdoiorg1011552014679192

2 International Journal of Corrosion

cough The aerial plant of Mollugo cerviana was collectednear Sathankulam Tuticorin district Tamil Nadu India inJuly 2010 The plant was identified and authenticated by DrV Chelladurai Research Officer (Rted) Botanist and thespecimen was deposited at Department of Botany AuxiliumCollege Vellore

The objective of this study is to evaluate the inhibitiveeffect of methanolic extract of M cerviana as a greencorrosion inhibitor on the mild steel in 1M HCl solutionThe corrosion performance was studied using different tech-niques like potentiodynamic polarization electrochemicalimpedance spectroscopy (EIS) and weight loss methodsThe scanning electron microcopy (SEM) was used for itsmorphological studies

2 Materials and Methods

21 Preparation of the Plant Extract The fresh aerial partsof M cerviana (500 g) were washed with water air driedpowdered and extracted with methanol (Merck) for 24 hrsThe methanolic solution was filtered and refluxed further toget a concentrated solutionThe clear dark brownmethanolicconcentrated solution was dried under vacuum to get asemisolid liquid and it was stored in air tight container andpreserved in the refrigerator for the further studies

22 Preparation of Specimen Mild steel specimens havingnominal composition of 0023P 004Si 0017Ni 037Mn 0078 C 002 S 0002 Mo Fe balance were usedSpecimens of dimension 3 times 3 times 01 cm and 1 times 1 times 01 cmwere used for weight loss and electrochemical studies Thespecimens were embedded in epoxy resin leaving a workingarea of 1 cm2 The surface preparation of the mechanicallyabraded specimens was carried out using different grades ofsilicon carbide emery paper (up to 1200 grit) and subsequentcleaning with acetone and rinsing with double-distilled waterwere done before each experiment

23 Electrolyte The electrolyte of 1MHCl solution wasprepared by diluting 37HCl (Merck) using double-distilledwater which is used as a corrosive solution The five concen-trations ofM cerviana extract varied from 25 to 1000mgL

24 Electrochemical Measurements Electrochemical meas-urements including potentiodynamic polarization curvesand electrochemical impedance spectroscopy (EIS) wereperformed in a conventional three electrode cell usinga computer-controlled potentiostatgalvanostat (AutolabPGSTAT 302N potentiostat from Eco-Chemie Netherlands)Platinum electrode was used as the counter electrodeAgAgCl and 3M KCl as the reference electrode andthe mild steel specimen was used as a working electrode(WE) The area of the WE exposed to the solution wasapproximately 1 cm2

Before each potentiodynamic polarization (Tafel) andelectrochemical impedance spectroscopy (EIS) studies theelectrode was allowed to corrode freely and its open circuitpotential (OCP) was recorded as a function of time up to20min which was sufficient to attain a stable state After

this a steady-state of OCP corresponding to the corrosionpotential (119864corr) of the working electrode was obtained Thepotentiodynamic measurements were started from cathodicto the anodic direction (119864 = 119864corr plusmn 250mV) at a scan rateof 10mVsminus1 Electrochemical impedance spectroscopy mea-surements were carried out using AC signals at the amplitudeof 10mV and measurement frequency from 100 kHzndash10mHzat the stable OCP Fresh solution and fresh mild steel sampleswere used after each sweep

25 Weight Loss Method Triplicate steel specimens wereimmersed in 100mL of electrolyte with and without the Mcerviana extract for 1 24 and 72 hrs at room temperatureThecleaned specimens were weighed before and after immersioninto the corrosive solution The specimens were removedrinsed with water and acetone and dried The loss of weightof the steel samples was determined using an analyticalbalance with the precision of 00001 plusmn 01mg The weightloss measurements were performed according to ASTMstandard G 31-72 The percentage inhibition efficiency (IE)was obtained from the following equation

IE =1198820minus1198821

1198820

times 100 (1)

where 1198820and 119882

1are the weight of the mild steel in the

absence and in the presence of inhibitor

26 Surface Analysis The surface morphology of mild steelspecimens immersed in 1MHCl in the absence and presenceof 500mgL of M cerviana extract at room temperaturefor 2 hrs was studied using Leica S440i a scanning electronmicroscope (SEM) operated at a voltage of 20 kV with probecurrent 100 pA

3 Results and Discussion

31 Potentiodynamic Polarization The potentiodynamicanodic and cathodic polarization plots for mild steelspecimens in 1M HCl solution with and without the plantextract M cerviana at five different concentrations aregiven in Figure 1 The respective electrochemical parametersincluding the values of corrosion current density (119868corr)corrosion potential (119864corr) cathodic Tafel slope (119887

119888)

anodic Tafel slope (119887119886) inhibition efficiency (IE) and

surface coverage (120579) are given in Table 1 As the inhibitorconcentration increased the corrosion current densities ofmild steel decreased till 500mgL of plant extract [25 26]This behavior is due to the adsorption of the inhibitor presentin the plant extract on mild steelsolution interfaces In thisstudy the maximum corrosion potential of mild steel wasshifted to 20mV cathodically with respect to the blank Fromthe potentiodynamic polarization curves (Figure 1) it isevident that both the anodic and the cathodic reactions areinhibited So the M cerviana extracts act as a mixed typeinhibitor with predominant cathodic effect

The polarization resistance increased noticeably with theincrease in M cerviana concentration and the percentage ofIE values also increased with inhibitor concentrations Thepercentage of inhibition efficiency (IE) was calculated from

International Journal of Corrosion 3

Table 1 The electrochemical polarization parameters for mild steel in 1M HCl solution in the absence and in the presence of M cervianaextract at different concentrations

Concentration of the inhibitor (mgL) 119887119886(mVdec) 119887

119888(mVdec) 119864corr (mV) 119868corr (mAcm2) IE 120579

Blank (HCl) 7798 4326 minus45693 35123 mdash mdash25 6827 5143 minus43901 007 7797 078100 7721 5712 minus44721 005 8307 083250 9234 6040 minus44116 004 8309 083500 12514 8456 minus43682 003 8903 0891000 956 6553 minus44113 004 8809 088

minus060 minus055 minus050 minus045 minus040 minus035 minus030

10minus1

10minus2

10minus3

10minus4

10minus5

10minus6

10minus7

I(A

cm

2)

E (V versus AgAgCl)

(a)

(b)(c)(d)

(e)(f)

(a) blank(b) 25mgL(c) 100mgL

(d) 250mgL(e) 500mgL(f) 1000mgL

Figure 1 Tafel plots of mild steel in 1M HCl in the absence and inthe presence ofM cerviana at different concentrations

potentiodynamic polarisation curves based on the followingequation

IE =119894corr0 minus 119894corr

119894corrtimes 100 (2)

where 119894corr0 is the corrosion current density in the absenceof the inhibitor and 119894corr is the corrosion current density inthe presence of the inhibitor obtained from Tafel plots Thechosen plant extract showed the maximum IE of 89 at500mgLThe high inhibition efficiency was due to the bond-ing of the adsorbed film of the inhibitor on the steel surface[31]There is no significant change in corrosion potential withthe addition of the extracts at different concentrations Thesurface coverage is approximately 084 which is good to actas a corrosive inhibitor

32 Electrochemical Impedance Spectroscopy The Nyquistplots of mild steel in 1M HCl solution in the absence and inthe presence ofM cerviana extract at different concentrationas inhibitor during an immersion time of 20min at roomtemperature are given in Figure 2 The depression in thefigure is the characteristic of the inhomogeneities of themetal

0 200 400 600 800 10000

100

200

300

400

500

600

10mHz 10mHz

264Hz

02Hz

263Hz

71919Hz

100 kHz

0 5 10 15 20 25 300

2

4

6

8

10

12

14

minusZ998400998400

(Ωmiddotcm

2)

minusZ998400998400

(Ωmiddotcm

2)

Z998400 (Ωmiddotcm2)


Blank

Blank

25mgL100mgL

250mgL500mgL1000mgL

Figure 2 Nyquist plots for mild steel in 1MHCl in the absence andpresence ofMollugo cerviana at different concentrations

surface during corrosion [32] The diameter of the capacitiveloop stands for the resistance of the corrosion and it canbe seen that the resistance decreases significantly with thedecrease in diameter Considering the impedance diagramsthe size of the capacitive loop increased by increasing theconcentration of inhibitor The Nyquist impedance plotswere analyzed by fitting the experimental data to a simpleequivalent circuit model given in Figure 3

In this equivalent circuit (Figure 3) 119877119904is the solution

resistance 119877ct is the charge transfer resistance and CPE is aconstant phase element which is placed in parallel to chargetransfer resistance element Thus in these situations puredouble layer capacitors are better described by a transferfunction with constant phase elements (CPE) to give a moreaccurate fit [33] and its impedance is given by

119885 = 119860minus1(119894120596)minus119899 (3)

where 119860 is proportionality coefficient 120596 is the angularfrequency 119894 is the imaginary number and 119899 is an exponentrelated to the phase shift and can be used as a measure ofsurface irregularity


Table 2 The electrochemical impedance spectroscopy parameters for mild steel in 1M HCl solution in the absence and presence of Mcerviana extract at different concentrations

Concentration of the inhibitor (mgL) CPE (120583Fcm2) 119877119904(Ωsdotcm2) 119877

119901(Ωsdotcm2) 119877ct (Ωsdotcm

2) IE 120579

Blank 009 106 05011 02867 mdash mdash25 006 135 28978 37486 9237 092100 004 078 38187 46220 9381 094250 005 117 53359 62113 9536 095500 005 108 83967 93793 9695 0971000 004 089 62867 74261 9695 097

Rct

Rs

CPE

Figure 3 Equivalent circuit model used to fit the metalsolutioninterface

For ideal electrodes when 119899 = 1 CPE can be consideredas a real capacitor The charge transfer resistance (119877ct) valuesare calculated based on the difference in impedance atlower and higher frequencies According to the Helmholtzthe decrease in CPE can be attributed to increase in thethickness of the electrical double layer [34] In EIS studiesthe inhibition efficiency was calculated using (4)

IE =119877ct minus 119877ct0119877cttimes 100 (4)

where 119877ct and 119877ct0 are charge transfer resistance in presenceand absence of inhibitor obtained from the electrochemicalimpedance diagrams The quantitative results of impedancemeasurements are given in Table 2 From the table result it isclear that by increasing the inhibitor concentration the CPEvalues tend to decrease and the 119877ct values increase Polariza-tion resistance increases from 501 to 8397Ω cm2 and doublelayer capacitance decreases from 0092 to 0046 120583Fcm2with the increase of M cerviana extract concentration Thesolution resistance is approximately constant The decreasein this capacitor values can be attributed to the formationof a protective layer on the electrode surface [35] Theincrease in the polarization resistance leads to an increasein inhibition efficiency The results also indicate that theincrease of charge transfer resistance is related to a decreasein the double layer capacitance up to 500mgL The effectis reversed with further increase in the concentration ofthe extract as seen in the result As the concentration ofthe plant extract increased above 500mgL the corrosionresistance decreased In fact the highest inhibition efficiencywas reached at 500mgL of the plant extract which is consid-ered to be an optimum inhibitor concentration The surface

Table 3 Mild steel weight loss data in 1M HCl solution in theabsence and in the presence of M cerviana extract at differentconcentrations at different time at room temperature

Concentration of theinhibitor (mgL)

Inhibition efficiency ()120579

1 h 24 h 72 hBlank mdash mdash mdash mdash25 2564 3883 7514 075100 4409 6029 8609 086250 6289 7002 9211 092500 6519 8876 9263 0921000 645 8025 9230 092

coverage is approximately 095 which is found to be good toact as an anticorrosive agent The results obtained from EISmethod is in good agreement with the linear polarization andweight loss measurements

33 Weight Loss Method Weight loss data of mild steelin 1MHCl in the absence and in the presence of variousconcentrations of inhibitor were obtained This physicalmeasurement is a direct answer to find out corrosive environ-ments and the average corrosion rate The variation of inhi-bition efficiency at different immersion times like 1 24 and72 hrs at room temperature in 1MHCl is shown in Table 3It has been observed that 500mgL of M cerviana extractis considered to be an optimum concentration that exhibitshigher efficiency against corrosion of mild steel The resultsfrom the Table 3 also show that the corrosion rate decreaseswith increase in the concentration of the inhibitor in HCland the maximum surface coverage is found to be 0926at 500mgL There is considerable decrease in inhibitionefficiency above 500mgL The inefficiency above 500mgLmay be due to weakening of metal-inhibitor interactionsresulting in the replacement of inhibitor by water or chlo-rine ions with decrease in inhibition efficiency [36] Theincreasing inhibition efficiency and decreasing corrosion ratewere attributed to the adsorption of inhibitor on the metalsurface From this result it is clear that the extract is adsorbedat the corrosion sites of mild steel surface responsible foranticorrosion activity The mild steel gets blocked and theadsorbed film of inhibitor acts as a physical barrier betweenmild steel and corrosion medium


0 200 400 600 800 1000

0

200

400

600

800

1000

1200

Cin

h120579

Cinh (mgL)

EISWeight lossPotentiodynamic polarization

Figure 4 Langmuir adsorption isotherms for mild steel in 1M HCl solution of M cerviana at different concentrations by EIS potentiody-namic polarization and weight loss methods

(a) (b)

(c)

Figure 5 SEM images of (a) mild steel (b) mild steel without inhibitor (and c) mild steel with inhibitor at 500mgL with the magnificationof 1500x

The inhibition increased with an increase in the immer-sion time and stabilized after 72 hrs with the inhibitionrate of 926 The results obtained from the weight lossmeasurement are in good agreement with those obtainedfrom the other electrochemical methods

34 Adsorption Isotherm The interaction between aninhibitor and the mild steel surface can be described by theadsorption isotherm To obtain the adsorption isotherm thedegree of surface coverage is calculated from the equation120579 = IE100 It was determined at different inhibitor


concentration using Langmuir adsorption isotherm and itcan be expressed as

119862inh120579

=

1

119870

+ 119862inh (5)

where119870 is equilibrium constant of adsorption and119862inh is theinhibition concentration Many researchers have explainedthe Langmuir adsorption isotherm with an interaction ofadsorbed species on the metallic surfaces [37 38] TheLangmuir adsorption isotherm was drawn by plotting 119862inh120579versus 119862inh considering the 120579 values from weight lossmethod at 72 hrs potentiodynamic polarization and EISmeasurements at room temperature for mild steel in 1MHCl at different concentration of inhibitors and the graphis shown in Figure 4 The straight line obtained in the graphclearly shows that the chosen inhibitor obeys the Langmuiradsorption isotherm From this it can be concluded thatthe M cerviana extract can act as a good inhibitor againstcorrosive materials

35 Surface Analysis The surface analysis was carried outusing SEM for the mild steel surface immersed in 1M HClsolution in the absence and in the presence of 500mgL ofinhibitor The SEM images of the mild steel 1M HCl andwith the inhibitor are given in Figure 5 A significant surfacedamage was observed on the mild steel which was immersedin 1MHCl solution (Figure 5(b)) indicating that the surface ishighly corrodedThe surface of the corroded area of the mildsteel (5B) was protected with the addition of the inhibitoras is evident from the surface morphology (Figure 5(c)) andthe presence of the inhibitor at the optimum concentrationexhibited a smooth surface indicating restricted corrosionunlike 5B The SEM images clearly indicate that the mildsteel surface was protected from corrosion in the presence ofplant extract which is acting as a corrosion inhibitor In otherwords theM cerviana extract inhibits corrosion ofmild steelin 1M HCl solution These results are in good agreementwith the other methods like electrochemical and weight lossmeasurements

4 Conclusion

M cerviana extracts acted as an effective corrosion inhibitorfor mild steel in 1M HCl solution The polarization studiesshowed that M cerviana extract was a mixed type inhibitorand its corrosion efficiency increased with the inhibitorconcentration From the EIS plots of mild steel it is clearthat the charge transfer resistance increased with increasein M cerviana extract Inhibition efficiency obtained fromweight loss measurements was in good agreement withpolarization and EIS methods The adsorption of the Mcerviana extracts of mild steel in 1M HCl solution obeys theLangmuir adsorption isotherm and the SEM studies showedthe formation of inhibitor film on mild steel surface

Conflict of Interests

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

Acknowledgment

The authors are grateful to Mrs Anju M Pillai ThermalSystems Group ISRO Satellite Centre Bangalore 560 017India for her invaluable guidance and support

References

[1] M Christov and A Popova ldquoAdsorption characteristics of cor-rosion inhibitors from corrosion ratemeasurementsrdquoCorrosionScience vol 46 no 7 pp 1613ndash1620 2004

[2] P C Okafor X Liu and Y G Zheng ldquoCorrosion inhibitionof mild steel by ethylamino imidazoline derivative in CO

2-

saturated solutionrdquoCorrosion Science vol 51 no 4 pp 761ndash7682009

[3] L Herrag B Hammouti S Elkadiri et al ldquoAdsorption prop-erties and inhibition of mild steel corrosion in hydrochloricsolution by some newly synthesized diamine derivatives exper-imental and theoretical investigationsrdquo Corrosion Science vol52 no 9 pp 3042ndash3051 2010

[4] S Cheng S Chen T Liu X Chang and Y Yin ldquoCar-boxymethylchitosan + Cu2+ mixture as an inhibitor used formild steel in 1 M HClrdquo Electrochimica Acta vol 52 no 19 pp5932ndash5938 2007

[5] L R Chauhan and G Gunasekaran ldquoCorrosion inhibition ofmild steel by plant extract in dilute HCl mediumrdquo CorrosionScience vol 49 no 3 pp 1143ndash1161 2007

[6] E Bayol T Gurten A A Gurten and M Erbil ldquoInteractionsof some Schiff base compounds with mild steel surface inhydrochloric acid solutionrdquo Materials Chemistry and Physicsvol 112 no 2 pp 624ndash630 2008

[7] P C Okafor and Y Zheng ldquoSynergistic inhibition behaviourof methylbenzyl quaternary imidazoline derivative and iodideions on mild steel in H

2SO4solutionsrdquo Corrosion Science vol

51 no 4 pp 850ndash859 2009[8] Z Zhang S Chen Y Li S Li and L Wang ldquoA study of the

inhibition of iron corrosion by imidazole and its derivatives self-assembled filmsrdquo Corrosion Science vol 51 no 2 pp 291ndash3002009

[9] M Mahdavian and M M Attar ldquoElectrochemical behaviour ofsome transition metal acetylacetonate complexes as corrosioninhibitors for mild steelrdquo Corrosion Science vol 51 no 2 pp409ndash414 2009

[10] X Liu P C Okafor and Y G Zheng ldquoThe inhibition ofCO2corrosion of N80 mild steel in single liquid phase

and liquidparticle two-phase flow by aminoethyl imidazolinederivativesrdquo Corrosion Science vol 51 no 4 pp 744ndash751 2009

[11] T Arslan F Kandemirli E E Ebenso I Love and H AlemuldquoQuantum chemical studies on the corrosion inhibition of somesulphonamides on mild steel in acidic mediumrdquo CorrosionScience vol 51 no 1 pp 35ndash47 2009

[12] F G Liu M Du J Zhang and M Qiu ldquoElectrochemicalbehavior of Q235 steel in saltwater saturated with carbon diox-ide based on new imidazoline derivative inhibitorrdquo CorrosionScience vol 51 no 1 pp 102ndash109 2009

[13] J M Roque T Pandiyan J Cruz and E Garcıa-OchoaldquoDFT and electrochemical studies of tris(benzimidazole-2-ylmethyl)amine as an efficient corrosion inhibitor for carbonsteel surfacerdquoCorrosion Science vol 50 no 3 pp 614ndash624 2008

[14] Z Ait Chikh D Chebabe A Dermaj et al ldquoElectrochemicaland analytical study of corrosion inhibition on carbon steel


in HCl medium by 112-bis(124-triazolyl)dodecanerdquo CorrosionScience vol 47 no 2 pp 447ndash459 2005

[15] A Rauscher G Kutsan and Z Lukacs ldquoStudies on the mech-anisms of corrosion inhibition by acetylenic compounds inhydrochloric acid solutionrdquo Corrosion Science vol 35 no 5ndash8pp 1425ndash1430 1993

[16] Z Ahmad Principles of Corrosion Engineering and CorrosionControl Butterworth-Heinemann London UK 2006

[17] H Ashassi-Sorkhabi and E Asghari ldquoEffect of hydrodynamicconditions on the inhibition performance of l-methionine as aldquogreenrdquo inhibitorrdquoElectrochimicaActa vol 54 no 2 pp 162ndash1672008

[18] E E Oguzie ldquoStudies on the inhibitive effect ofOccimum viridisextract on the acid corrosion of mild steelrdquo Journal of Materialschemistry and physics vol 99 no 2-3 pp 441ndash446 2006

[19] P C Okafor M E Ikpi I E Uwah E E Ebenso U J Ekpe andS AUmoren ldquoInhibitory action of Phyllanthus amarus extractson the corrosion of mild steel in acidic mediardquo CorrosionScience vol 50 no 8 pp 2310ndash2317 2008

[20] 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

[21] K M Ismail ldquoEvaluation of cysteine as environmentallyfriendly corrosion inhibitor for copper in neutral and acidicchloride solutionsrdquo Electrochimica Acta vol 52 no 28 pp 7811ndash7819 2007

[22] K Srivastava and P Srivastava ldquoStudies on plant materials ascorrosion inhibitorsrdquo British Corrosion Journal vol 16 no 4pp 221ndash223 1981

[23] A M Abdel-Gaber E Khamis H Abo-ElDahab and S AdeelldquoInhibition of aluminium corrosion in alkaline solutions usingnatural compoundrdquo Journal of Materials Chemistry and Physicsvol 109 no 2-3 pp 297ndash305 2008

[24] A M Abdel-Gaber ldquoEffect of immersion time and temperatureon the inhibition of the acid corrosion of zinc by fenugreekseeds extractrdquo International Journal of Applied Chemistry vol3 p 161 2007

[25] I H Farooqi M A Quraishi and P A Saini ldquoNaturalcompounds as cooling water inhibitors for cooling systemsrdquo inProceedings of the EUROCORRrsquo97 vol 2 p 347 1997

[26] M A Quraishi ldquoInvestigation of some green compounds ascorrosion and scale inhibitors for cooling systemsrdquo Corrosionvol 55 no 5 pp 493ndash497 1999

[27] Y Li P Zhao Q Liang and B Hou ldquoBerberine as a naturalsource inhibitor for mild steel in 1 M H

2SO4rdquo Applied Surface

Science vol 252 no 5 pp 1245ndash1253 2005[28] P Sakthivel P V Nirmala S Umamaheswari et al ldquoCorrosion

inhibition of mild steel by extracts of Pongamia Glabra andAnnona Squamosa in acidic mediardquo Bulletin of Electrochem-istry vol 15 no 2 pp 83ndash86 1999

[29] R Kanojia and G Singh ldquoAn interesting and efficient organiccorrosion inhibitor for mild steel in acidic mediumrdquo SurfaceEngineering vol 21 no 3 pp 180ndash186 2005

[30] H Al-Sehaibani ldquoEvaluation of extracts of Henna leaves asenvironmentally friendly corrosion inhibitors formetalsrdquoMate-rialwissenschaft und Werkstofftechnik vol 31 no 12 pp 1060ndash1063 2000

[31] E Khamis and N M Al Andis ldquoHerbs as new type of greeninhibitors for acidic corrosion of steelrdquoMaterialwissWerkst vol33 no 9 pp 550ndash554 2002

[32] V R Saliyan and A V Adhikari ldquoQuinolin-5-ylmethylene-3-[8-(trifluoromethyl)quinolin-4-yl]thiopropanohydrazide as aneffective inhibitor of mild steel corrosion in HCl solutionrdquoCorrosion Science vol 50 no 1 pp 55ndash61 2008

[33] I D Raistrick D R Franceschetti and J R MacdonaldImpedance Spectroscopy Theory Experimental and Applica-tions JohnWileyamp SonsHobokenNJ USA 2nd edition 2005E Barsoukov J R Macdonald Eds

[34] Y Tang X Yang W Yang R Wan Y Chen and X Yin ldquoApreliminary investigation of corrosion inhibition of mild steelin 05 M H2SO4 by 2-amino-5-(n-pyridyl)-134-thiadiazolepolarization EIS and molecular dynamics simulationsrdquo Corro-sion Science vol 52 no 5 pp 1801ndash1808 2010

[35] M Lebrini M Lagrenee H Vezin M Traisnel and F BentissldquoExperimental and theoretical study for corrosion inhibition ofmild steel in normal hydrochloric acid solution by some newmacrocyclic polyether compoundsrdquo Corrosion Science vol 49no 5 pp 2254ndash2269 2007

[36] G Gunasekaran and L R Chauhan ldquoEco friendly inhibitor forcorrosion inhibition of mild steel in phosphoric acid mediumrdquoElectrochimica Acta vol 49 no 25 pp 4387ndash4395 2004

[37] E Bayol K Kayakirilmaz and M Erbil ldquoThe inhibitive effectof hexamethylenetetramine on the acid corrosion of steelrdquoMaterials Chemistry and Physics vol 104 no 1 pp 74ndash82 2007

[38] L Tang G Mu and G Liu ldquoThe effect of neutral red on thecorrosion inhibition of cold rolled steel in 10 M hydrochloricacidrdquo Corrosion Science vol 45 no 10 pp 2251ndash2262 2003

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Journal ofNanomaterials


cough The aerial plant of Mollugo cerviana was collectednear Sathankulam Tuticorin district Tamil Nadu India inJuly 2010 The plant was identified and authenticated by DrV Chelladurai Research Officer (Rted) Botanist and thespecimen was deposited at Department of Botany AuxiliumCollege Vellore

The objective of this study is to evaluate the inhibitiveeffect of methanolic extract of M cerviana as a greencorrosion inhibitor on the mild steel in 1M HCl solutionThe corrosion performance was studied using different tech-niques like potentiodynamic polarization electrochemicalimpedance spectroscopy (EIS) and weight loss methodsThe scanning electron microcopy (SEM) was used for itsmorphological studies

2 Materials and Methods

21 Preparation of the Plant Extract The fresh aerial partsof M cerviana (500 g) were washed with water air driedpowdered and extracted with methanol (Merck) for 24 hrsThe methanolic solution was filtered and refluxed further toget a concentrated solutionThe clear dark brownmethanolicconcentrated solution was dried under vacuum to get asemisolid liquid and it was stored in air tight container andpreserved in the refrigerator for the further studies

22 Preparation of Specimen Mild steel specimens havingnominal composition of 0023P 004Si 0017Ni 037Mn 0078 C 002 S 0002 Mo Fe balance were usedSpecimens of dimension 3 times 3 times 01 cm and 1 times 1 times 01 cmwere used for weight loss and electrochemical studies Thespecimens were embedded in epoxy resin leaving a workingarea of 1 cm2 The surface preparation of the mechanicallyabraded specimens was carried out using different grades ofsilicon carbide emery paper (up to 1200 grit) and subsequentcleaning with acetone and rinsing with double-distilled waterwere done before each experiment

23 Electrolyte The electrolyte of 1MHCl solution wasprepared by diluting 37HCl (Merck) using double-distilledwater which is used as a corrosive solution The five concen-trations ofM cerviana extract varied from 25 to 1000mgL

24 Electrochemical Measurements Electrochemical meas-urements including potentiodynamic polarization curvesand electrochemical impedance spectroscopy (EIS) wereperformed in a conventional three electrode cell usinga computer-controlled potentiostatgalvanostat (AutolabPGSTAT 302N potentiostat from Eco-Chemie Netherlands)Platinum electrode was used as the counter electrodeAgAgCl and 3M KCl as the reference electrode andthe mild steel specimen was used as a working electrode(WE) The area of the WE exposed to the solution wasapproximately 1 cm2

Before each potentiodynamic polarization (Tafel) andelectrochemical impedance spectroscopy (EIS) studies theelectrode was allowed to corrode freely and its open circuitpotential (OCP) was recorded as a function of time up to20min which was sufficient to attain a stable state After

this a steady-state of OCP corresponding to the corrosionpotential (119864corr) of the working electrode was obtained Thepotentiodynamic measurements were started from cathodicto the anodic direction (119864 = 119864corr plusmn 250mV) at a scan rateof 10mVsminus1 Electrochemical impedance spectroscopy mea-surements were carried out using AC signals at the amplitudeof 10mV and measurement frequency from 100 kHzndash10mHzat the stable OCP Fresh solution and fresh mild steel sampleswere used after each sweep

25 Weight Loss Method Triplicate steel specimens wereimmersed in 100mL of electrolyte with and without the Mcerviana extract for 1 24 and 72 hrs at room temperatureThecleaned specimens were weighed before and after immersioninto the corrosive solution The specimens were removedrinsed with water and acetone and dried The loss of weightof the steel samples was determined using an analyticalbalance with the precision of 00001 plusmn 01mg The weightloss measurements were performed according to ASTMstandard G 31-72 The percentage inhibition efficiency (IE)was obtained from the following equation

IE =1198820minus1198821

1198820

times 100 (1)

where 1198820and 119882

1are the weight of the mild steel in the

absence and in the presence of inhibitor

26 Surface Analysis The surface morphology of mild steelspecimens immersed in 1MHCl in the absence and presenceof 500mgL of M cerviana extract at room temperaturefor 2 hrs was studied using Leica S440i a scanning electronmicroscope (SEM) operated at a voltage of 20 kV with probecurrent 100 pA

3 Results and Discussion

31 Potentiodynamic Polarization The potentiodynamicanodic and cathodic polarization plots for mild steelspecimens in 1M HCl solution with and without the plantextract M cerviana at five different concentrations aregiven in Figure 1 The respective electrochemical parametersincluding the values of corrosion current density (119868corr)corrosion potential (119864corr) cathodic Tafel slope (119887

119888)

anodic Tafel slope (119887119886) inhibition efficiency (IE) and

surface coverage (120579) are given in Table 1 As the inhibitorconcentration increased the corrosion current densities ofmild steel decreased till 500mgL of plant extract [25 26]This behavior is due to the adsorption of the inhibitor presentin the plant extract on mild steelsolution interfaces In thisstudy the maximum corrosion potential of mild steel wasshifted to 20mV cathodically with respect to the blank Fromthe potentiodynamic polarization curves (Figure 1) it isevident that both the anodic and the cathodic reactions areinhibited So the M cerviana extracts act as a mixed typeinhibitor with predominant cathodic effect

The polarization resistance increased noticeably with theincrease in M cerviana concentration and the percentage ofIE values also increased with inhibitor concentrations Thepercentage of inhibition efficiency (IE) was calculated from







10minus1

10minus2

10minus3

10minus4

10minus5

10minus6

10minus7

I(A

cm

2)

E (V versus AgAgCl)

(a)

(b)(c)(d)

(e)(f)


(d) 250mgL(e) 500mgL(f) 1000mgL




119894corrtimes 100 (2)



0 200 400 600 800 10000

100

200

300

400

500

600

10mHz 10mHz

264Hz

02Hz

263Hz

71919Hz

100 kHz

0 5 10 15 20 25 300

2

4

6

8

10

12

14

minusZ998400998400

(Ωmiddotcm

2)

minusZ998400998400

(Ωmiddotcm

2)



Blank

Blank

25mgL100mgL

250mgL500mgL1000mgL





119885 = 119860minus1(119894120596)minus119899 (3)






2) IE 120579


Rct

Rs

CPE












0 200 400 600 800 1000

0

200

400

600

800

1000

1200

Cin

h120579

Cinh (mgL)



(a) (b)

(c)






119862inh120579

=

1

119870

+ 119862inh (5)



4 Conclusion




Acknowledgment


References



2-




















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials









10minus1

10minus2

10minus3

10minus4

10minus5

10minus6

10minus7

I(A

cm

2)

E (V versus AgAgCl)

(a)

(b)(c)(d)

(e)(f)


(d) 250mgL(e) 500mgL(f) 1000mgL




119894corrtimes 100 (2)



0 200 400 600 800 10000

100

200

300

400

500

600

10mHz 10mHz

264Hz

02Hz

263Hz

71919Hz

100 kHz

0 5 10 15 20 25 300

2

4

6

8

10

12

14

minusZ998400998400

(Ωmiddotcm

2)

minusZ998400998400

(Ωmiddotcm

2)



Blank

Blank

25mgL100mgL

250mgL500mgL1000mgL





119885 = 119860minus1(119894120596)minus119899 (3)






2) IE 120579


Rct

Rs

CPE












0 200 400 600 800 1000

0

200

400

600

800

1000

1200

Cin

h120579

Cinh (mgL)



(a) (b)

(c)






119862inh120579

=

1

119870

+ 119862inh (5)



4 Conclusion




Acknowledgment


References



2-




















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials







2) IE 120579


Rct

Rs

CPE












0 200 400 600 800 1000

0

200

400

600

800

1000

1200

Cin

h120579

Cinh (mgL)



(a) (b)

(c)






119862inh120579

=

1

119870

+ 119862inh (5)



4 Conclusion




Acknowledgment


References



2-




















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0 200 400 600 800 1000

0

200

400

600

800

1000

1200

Cin

h120579

Cinh (mgL)



(a) (b)

(c)






119862inh120579

=

1

119870

+ 119862inh (5)



4 Conclusion




Acknowledgment


References



2-




















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





119862inh120579

=

1

119870

+ 119862inh (5)



4 Conclusion




Acknowledgment


References



2-




















































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 Evaluation of Corrosion ... - Hindawi

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