research article isomers of poly aminophenol: chemical...

Research ArticleIsomers of Poly Aminophenol Chemical SynthesisCharacterization and Its Corrosion Protection Aspect onMild Steel in 1 M HCl

G Thenmozhi P Arockiasamy and R Jaya Santhi

PG and Research Department of Chemistry Auxilium College Vellore Tamil Nadu 632006 India

Correspondence should be addressed to R Jaya Santhi shanthijaya02gmailcom

Received 11 December 2013 Accepted 27 January 2014 Published 17 March 2014

Academic Editor Sheng S Zhang

Copyright copy 2014 G Thenmozhi et al This 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 oxidative chemical polymerizations of three isomers of aminophenol ortho meta and para (PoAP PmAP and PpAP) wereperformed in aqueous HCl using ammonium persulfate as an oxidant at 0ndash3∘C The synthesized polymers were characterized byemploying elemental analysis GPC UV-VIS-NIR FT-IR XRD and TGA The corrosion inhibition effect of these three polymerson mild steel in 1M HCl solution was studied by using electrochemical techniques such as potentiodynamic polarization andelectrochemical impedance spectroscopy These measurements reveal that the inhibition efficiency obtained by these polymersincreased by increasing their concentration The inhibition efficiency follows the order PpAP gt PoAP gt PmAPThe results furtherrevealed that PpAP at a concentration of 250mgL furnishes maximum inhibition efficiency (965) Polarization studies indicatedthat these three polymers act as the mixed type corrosion inhibitors

1 Introduction

Mild steel (MS) continues to be the prime constructionmaterial for a wide range of structures as it has favorableproperties and high speed of fabrication However its corro-sion resistance is highly weakened when it is exposed to anacid environment [1ndash3] Corrosion ofMSwill result in the lossof its mechanical properties and structural integrity [4] Atthis juncture it is necessary to protect it from corrosionwhenit is designed for long term service A generic way to protectthe material from corrosion is to apply protective coatings[5 6] Among the various types of protective coatings thatare in use organic polymers play important roles in corrosionprevention These include organic inhibitors generally richin Π bonds which adsorb onto a metal surface to reducethe number of active sites and barrier coatings which slowthe transport of corrosive agents to the metal and removalof corrosion products [7] The use of conducting polymersfor the protection of metals against corrosion has been onlyrecently investigated

Unlike aniline and other substituted anilines amino phe-nols present two oxidizable groups (NH

2and OH) providing

more reactive sites In principle they could present elec-trochemical behavior resembling anilines andor phenolsbeing an important condition for polymerization the relativeposition of the amino and hydroxyl groups in the aromaticring [8] The earlier studies [9ndash11] have shown that inhibitiveproperties of polyaniline and its derivatives on the corrosionof iron in acid solution are due to the presence of 120587 electronsquaternary nitrogen atom and the large molecular size ofthem The protection of metal surface against corrosion byaromatic diamine and aminophenol based polymers wasreported on iron [12] copper [13]mild steel [14] and stainlesssteel [15] In addition it has been suggested that a derivativeof aniline such as phenylenediamine and o-aminophenolpolymers exhibits excellent anticorrosion properties [16 17]To the best of our knowledge there was no report in theliterature dealing with the corrosion protection behavior ofisomers of poly aminophenols on MS and on other activemetals synthesized by chemical oxidation method

In this present work isomers of aminophenol weresynthesized by chemical oxidation method and character-ized by different spectroscopic techniques An attempt hasbeen made to investigate the corrosion protection behaviour

Hindawi Publishing CorporationInternational Journal of ElectrochemistryVolume 2014 Article ID 961617 11 pageshttpdxdoiorg1011552014961617

2 International Journal of Electrochemistry

of chemically synthesised poly (ortho- meta- and para-aminophenol) overMS in acidic environment using potentio-dynamic polarisation and electrochemical impedance spec-troscopy (EIS) measurements

2 Experimental Method

21 Synthesis of the Polymers 01M monomers (ortho-meta- and para-aminophenol) and 1M HCl were taken inseparate beakers containing 50mL toluene Polymerizationreactions were started by drop wise addition of aqueoussolution of APS 01M (228 g) APS in 100mL distilled waterand the reactions were carried out for 12 h at 0ndash3∘C withconstant stirring Polymerizations were stopped by additionof 50mLmethanolThe resulting precipitated polymers werefiltrated and washed with excess amount of water methanoland acetone to remove excess of HCl and APS The powderof PoAP PmAP and PpAP was then dried at 50∘C for 24 hBased on our observation as well as spectral and elementalanalyses of the three synthesized polymers we have proposedpolymerization reactions as shown in Schemes 1 2 and 3

22 Characterization Molecular weights of polymerswere determined by gel permeation chromatographyusing Styragel columns and a refractive detector (Watersmodel R 4000) with THF as the mobile phase Carbon-hydrogen-nitrogen analyses of polymers were carried outby a microanalytical technique using an Elementar VarioEL 3 elemental analyzer UV-VIS-NIR spectra of polymersdissolved in DMSO solvent were obtained using VarianCary-5000 spectrophotometer in the range of 200ndash2500 nmThe FT-IR spectrums of polymers were recorded by ThermoNicolet Avatar 370 spectrophotometer The spectrum ofthe dry polymer powder in KBr pellet was recorded from500 cmminus1 to 4000 cmminus1 X-ray diffraction (XRD) scan wasdone with Bruker AXS D8 advance diffractometer at roomtemperature using Cu K120572 (120582 = 15406 A)Thermogravimetricanalysis (TGA) was carried out in nitrogen atmosphere ata heating rate 10∘Cmin up to 750∘C temperature by PerkinElmer Diamond TGDTA analyzer

Electrochemical measurements including potentiody-namic polarization curves and electrochemical impedancespectroscopy (EIS) were performed in a conventionalthree electrodes cell using a computer-controlled potentio-statgalvanostat (Autolab PGSTAT 302N potentiostat fromEco-chemie The Netherlands) Platinum electrode was usedas the counter electrode AgAgCl 3M KCl was used as thereference electrode and the mild steel specimen was used asa working electrode Specimen of dimension 1 times 1 times 01 cmwas used for electrochemical studies The specimens wereembedded in epoxy resin leaving a working area of 1 cm2Thesurface preparation of the mechanically abraded specimenswas carried out by using different grades of silicon carbideemery paper (up to 1200 grit) and subsequent cleaning withacetone and rinsing with double distilled water were donebefore each experiment

Before each potentiodynamic polarization (Tafel) and EISstudies the electrode was allowed to corrode freely and its

open circuit potential (OCP) was recorded as a function oftime up to 20min which was sufficient to attain a stablestate After this a steady state of OCP corresponding tothe corrosion potential (119864corr) of the working electrode wasobtained The potentiodynamic measurements were startedfrom cathodic to the anodic direction119864 = 119864corrplusmn250mV at ascan rate of 10mV sminus1The linear Tafel segments of the anodicand cathodic curves were extrapolated to obtain 119864corr andcorrosion current density (119868corr)The inhibition efficiencywasevaluated from the measured 119868corr with and without inhibitorusing the relationship

IE () =1198680

corr minus 119868corr

1198680

corrtimes 100 (1)

where 1198680corr is the corrosion current density without inhibitorand 119868corr is the corrosion current density with inhibitor Thecorrosion rates (CR) of MS with polymers were calculatedfrom polarization curves using the following equation [18]

CR =327 times 10

minus3

times 119868corr times EW119863

(2)

where CR is the corrosion rate (mmpy) 119868corr is the corrosioncurrent density (120583A cmminus2) EW is the equivalent weight ofthe specimen and119863 is the density (g cmminus3) of the specimenrespectively

EIS measurements were carried out using AC signals of10mV for the frequency spectrum from 100 kHz to 10mHzat the stable OCPThe potentiodynamic polarization and EISdata were analyzed and fitted using graphing and analyzingimpedance software Nova 14 Fresh solution and fresh steelsamples were used after each sweep The charge transferresistance (119877ct) was obtained from the diameter of thesemicircle of the Nyquist plot The inhibition efficiency ofthe inhibitor has been found out from the charge transferresistance values using the following equation

IE () =119877ct minus 119877

0

ct119877cttimes 100 (3)

where 1198770ct and 119877ct are the charge transfer resistance in theabsence and in the presence of the inhibitor

3 Results and Discussion

31 Elemental Analysis and Molecular Weight The elementalanalysis data of PoAP PmAP and PpAP are shown inTable 1 The PpAP contains higher H (44) and N (102)compared to other two polymers The result indicates somesulfur incorporated in these three polymers due to the saltformation of liberated sulfuric acid from the reduction ofoxidant APS with ndashNndash present within the polymer chain [19]

The molecular weights of the soluble portion of thesepolymers were determined by gel permeation chromatog-raphy performed in THF The number-average molecularweight (119872

119899) weight-average molecular weight (119872

119908) and

poly dispersity index (PDI = 119872119908119872119899) values were found

and listed in Table 1 For PmAP and PpAP the PDI values

International Journal of Electrochemistry 3

Step I

Step II

Step III

NH2

OH

OH

OH

OHOH

Resonance

N

N

N

O

O

O

H

n

∙

∙

(NH4)2S2O8

NH2

NH2

NH2

NH2

∙+

∙+

+

++

+

Poly(o-aminophenol)

2NH4++ S2O8

2minus

S2O82minus

2SO4minus∙

2SO4minus∙ + SO4

minus2

Scheme 1 Proposed mechanism of polymerization of o-aminophenol

Step I

Step II

Step III

NH2

NH2

HOHO

HO

HO

HO

HO

HO

HO HO

Resonance

N

N

N

N

NN

N

O

O

O

O

O

O

OH

H

H

H

HH

HH

H

H

HN

n

minuseminus

(NH4)2S2O8

∙

∙

∙

+SO2minus4

NH2 NH2

NH2

NH2

NH2

∙+

∙+

+

+

+

+NH2++∙ +

Dimer

Poly(m-aminophenol)

2NH4++ S2O8

2minus

S2O82minus

2SO4minus∙

+2SO4minus∙

Scheme 2 Proposed mechanism of polymerization ofm-aminophenol

4 International Journal of Electrochemistry

Step I

Step II

Step III

2SOminus∙4 +

Resonance

NN

N

N

N

O

O O

O

O

O

O

O

O

O

OHOH

O

O O O

NH

Hn

(NH4)2S2O8

∙

∙

∙

∙

NH2

NH2 NH2

NH2NH2

NH2NH2 NH2 NH2

∙+

Dimer

∙

∙

∙

∙+

∙+

+∙

minuse∙

+

Poly(p-aminophenol)

2NH4++ S2O8

2minus

S2O82minus

2SO4minus∙

+ SO42minus

Scheme 3 Proposed mechanism of polymerization of p-aminophenol

Table 1 Elemental analysis and molecular weights of isomers of aminophenol

Polymers Elemental analysis Molecular weightC () H () N () S () 119872

119899

119872119908

PDIPoAP 66 37 98 04 90000 297000 32PmAP 53 43 82 07 57000 60500 11PpAP 60 44 102 01 182000 297000 16

are found to be 11 and 16 these values demonstrated thatthe chromatograms were unimodal no traces of monomersoligomers or high molecular masses were detected and nocross-linking or other by-products originating from parasiticreactions were present [20] PoAP has the PDI value of 32suggesting the presence of small amount of oligomers in thepolymer sample Among these three polymers PpAP has high119872119899and119872

119908values this result was supported as above from

the elemental analysis result of PpAP

32 UV-VIS-NIR Spectroscopy The UV-VIS-NIR absorptionspectrums of all the polymers dissolved in DMSO are shownin Figure 1 The spectrums of all the polymers consist of twomajor absorption peaks the first peak at 285ndash305 nm (435ndash406 eV) is assigned to the 120587 minus 120587lowast transition of the phenylringswhich is related to the extent of conjugation between thephenyl rings in the polymer chainThe intensity of the 120587minus120587lowastabsorption maxima is comparable for all the three polymersThe second absorption peak at 571ndash620 nm is assigned to119899minus120587lowast transition between theHOMOorbital of the benzenoid

ring and the LUMO orbital of the quinoid ring It is sensitive

to the overall oxidation state of the polymer [21]The intensityof the peak around 850 nm is seen to be greater in the spectraof the PpAP compared to that of the other two polymers thispeak has been assigned to ndashNH

2

+ species which is generatedon doping or the polaronic transitions

33 FT-IRAnalysis Therepresentative FT-IR spectra of threepolymers are given in Figure 2 In all the polymers a broadpeak that appears in the region 3800ndash1800 cmminus1 is due tothe stretching of aromatic CndashH hydrogen bonded ndashOH andndashNHndash groups The ndashOH group is hydrogen bonded withnearest nitrogen of ndashNH group present in the polymer chainthrough the H

2O molecule present in all the polymers So

ndashOH absorption peak appears at about 3338 (sharp) 3375(broad) and 3270 cmminus1 (sharp) for PoAP PmAP and PpAPrespectively Two main peaks around 1600 and 1560 cmminus1in all the spectrums correspond respectively to the ring-stretching vibrations of the quinoid and benzenoid ringsThe presence of these two rings clearly shows that thepolymers are composed of the amine and imine units Thepeak appears around 2362 cmminus1 which is the characteristics

International Journal of Electrochemistry 5

500 1000 1500 2000 2500

(c)

(b)

(a)

Abso

rban

ce (a

u)

Wavelength (nm)

Figure 1 UV-VIS-NIR spectra of isomers of aminophenol (a) PoAP (b) PmAP and (c) PpAP

4000 3500 3000 2500 2000 1500 1000 500

(c)

(b)

(a)

Tra

nsm

ittan

ce (

)

Wave number (cmminus1)

Figure 2 FT-IR spectra of isomers of aminophenol (a) PoAP (b) PmAP and (c) PpAP

stretching band for C=C=NorC=C=O [22]The peak around1270 cmminus1 is assigned to the CndashN stretching vibrations of thesecond aromatic amine indicating the formation of a CndashNndashCstructure in the polymers whereas a peak at 2923 cmminus1 inPoAP and PpAP is assigned to stretching vibrations of C=Cin phenyl ring [23] In three polymers the peaks around1147 cmminus1 are ascribed to the stretching of the CndashOndashClinkages [24] and further support that the aminophenolchanged into poly aminophenol The peaks between 900 and600 cmminus1 correspond to CndashH bending of an aromatic ringsubstitution of the polymers

34 XRD Analysis Figure 3 shows the X-ray diffractionpatterns of three polymers The diffraction patterns weretypical of crystallineamorphous polymers The crystallineregions in the polymers are shown by the presence ofrelatively sharp peaks The amorphous regions are visible

by the broad low intensity halo accordingly the PoAP ismore crystalline than PpAP and PmAPThemore amorphousnature of PmAP was inferred from their diffraction patternsThe position of the Braggrsquos peaks (2120579) also gives informationon the morphology of the polymers All the polymersexhibit their strongest peaks at 176∘ 194∘ 242∘ and 255∘2120579 = 255∘ is characteristics of the van der Waals distancesbetween stacks of phenylene rings (poly aminophenol rings)[25] These strongest peaks indicate crystalline domains inthe amorphous structure of the polymers The degree ofcrystalline or ordered structural pattern in PoAP and PpAP isdue to the more intrachain hydrogen bonding or electrostaticinteraction (through both amine andor phenolic group)present in the polymer The crystallinity and orientation ofconducting polymers have been of much interest becausemore highly ordered systems can display a metallic conduc-tive state and may influence the anticorrosion performance[26]

6 International Journal of Electrochemistry

10 20 30 40 50 60 70

(c)

(b)

(a)

Inte

nsity

(au

)

2120579 (deg)

Figure 3 XRD patterns of isomers of aminophenol (a) PoAP (b) PmAP and (c) PpAP

100 200 300 400 500 600 7000

20

40

60

80

100

(c)

(b)(a)W

eigh

t (

)

Temperature (∘C)

Figure 4 TGA curves of isomers of aminophenol (a) PoAP (b) PmAP and (c) PpAP

35 Thermogravimetric Analysis The thermal stability ofthe three polymers was evaluated using thermogravimetricanalysis and shown in Figure 4The thermal behaviour of thethree polymers is similar and exhibits a three stage decompo-sition patternThefirst weight loss step starts from60 to 110∘Cwhich corresponds to the loss of water molecules adsorbedmoisture free acids and volatile molecules in polymermatrixThe second step is in the TGA curves between 180 and250∘C because of loss of dopant sublimation and removalof lowmolecular weight polymeroligomer from the polymermatrix While the third weight loss step occurs between 265and 360∘C which is due to the complete degradation anddecomposition of the polymer backbone The degradationtemperature of PpAP (480∘C) is higher than that of PoAP(400∘C) and PmAP (465∘C)

36 Potentiodynamic Polarization Studies The potentiody-namic polarization curves ofMS in 1MHClwith the addition

of various concentrations of PoAP PmAP and PpAP areshown in Figures 5(a) 5(b) and 5(c) respectively The cor-rosion kinetic parameters such as corrosion current density119868corr corrosion potential 119864corr anodic Tafel slope 119887

119886 and

cathodic Tafel slope 119887119888 inhibition efficiency IE and corrosion

rate CR deduced from the curves are given in Table 2 Thecorrosion current density values decrease from 3710 120583A cmminus2for the blank acid to 400 164 and 131120583A cmminus2 for PmAPPoAP and PpAP respectively for the addition of 250mg Lminus1three polymers resulting in 892 956 and 965 of inhibitionefficiency It is clear that the 119868corr values decrease with thepresence of three polymers which indicated that polymersadsorbed on the metal surface and hence inhibition occursAs the concentrations increase 25 to 500mg Lminus1 for PoAPand PmAP the IE increases 925 to 972 and 477 to 902respectively But for PpAP the IE reachedmaximum of 965at 250mg Lminus1 and further increase in concentration the IEvalue decreases The 119864corr 119887119886 and 119887119888 values do not change

International Journal of Electrochemistry 7

minus060 minus055 minus050 minus045 minus040 minus035 minus030

1E minus 6

1E minus 5

1E minus 4

1E minus 3

E (V vs AgAgCl)

Blank25mgL50mgL

100mgL250mgL500mgL

I(A

cm

2 )

(a)

minus060 minus055 minus050 minus045 minus040 minus035

1E minus 6

1E minus 5

1E minus 4

1E minus 3

E (V vs AgAgCl)

Blank25mgL50mgL

100mgL250mgL500mgL

I(A

cm

2 )

(b)

minus060 minus055 minus050 minus045 minus040 minus035

1E minus 6

1E minus 7

1E minus 8

1E minus 5

1E minus 4

1E minus 3

E (V vs AgAgCl)

Blank25mgL50mgL

100mgL250mgL500mgL

I(A

cm

2 )

(c)

Figure 5 (a) Potentiodynamic polarization curves obtained for mild steel in 1MHCl in the presence and absence of different concentrationsof PoAP (b) Potentiodynamic polarization curves obtained for mild steel in 1M HCl in the presence and absence of different concentrationsof PmAP (c) Potentiodynamic polarization curves obtained for mild steel in 1MHCl in the presence and absence of different concentrationsof PpAP

appreciably with the addition of the inhibitors indicating thatthe inhibitors are not interfering with the anodic dissolutionor cathodic hydrogen evolution reactions independently butacts as a mixed type of inhibitor [27 28] These resultsconfirm that the isomers of poly aminophenol on MS actas a highly protective layer which is mainly attributed tothe presence of 120587 electrons in aromatic ring coexisting withquaternary nitrogen atom and large molecular size [29]Moreover the outstanding corrosion protection offered byPpAP on MS may be due to the fact that the depositedpolymer is strongly adherent and uniformly covers the entireelectrode surface Based on the corrosion protection mech-anism put forth by several researchers [30ndash32] the polymer

accepts electrons from the metal and gives them to oxygenThis reaction generates the formation of a passive layer atthe polymermetal interface which lowers the corrosion rateand shifts the corrosion potential to more positive valuesBesides isomers of poly aminophenol is a ladder polymerhaving longer molecular structure with phenazine skeletonensures greater adsorption on the MS surface and decreasesthe effective area for the corrosion reaction by blocking thereaction sites [33 34]

37 Electrochemical Impedance Spectroscopy The Nyquistimpedance plots were analyzed by fitting the experimentaldata to a simple equivalent circuit model In this equivalent

8 International Journal of Electrochemistry

Table 2 Potentiodynamic polarization parameters for mild steel without and with different concentrations of isomers of aminophenol in 1MHCl

Inhibitor concentration(mgL) 119864corr (mV)

119868corr(120583Acm2)

119887119886

(mVdecade)119887119888

(mVdecade) IE () Corrosion rate(mmyear)

PoAPBlank 471 3710 61 43 mdash 200925 434 277 50 75 925 32150 445 254 75 56 932 295100 436 221 72 49 94 257250 437 164 70 54 956 190500 443 104 73 56 972 121

PmAPBlank 471 3710 61 43 mdash 200925 439 1938 77 42 477 120850 452 1040 56 52 72 882100 454 565 76 75 847 657250 444 400 93 59 892 465500 455 364 52 74 902 424

PpAPBlank 471 3710 61 43 mdash 200925 444 1041 58 41 72 88150 466 283 44 75 924 398100 469 196 81 50 947 227250 481 131 71 58 965 152500 458 244 40 51 934 284

circuit 119877119904is the solution resistance 119877ct is the charge transfer

resistance and CPE is a constant phase element which isplaced in parallel to charge transfer resistance element Thusin these situations pure double layer capacitors (119862dl) arebetter described by a transfer function with constant phaseelements to give a more accurate fit The Nyquist plots ofMS in 1M HCl in the presence and absence of variousconcentrations of PoAP PmAP and PpAP are depicted inFigures 6(a) 6(b) and 6(c) respectively The Nyquist spectraobtained for blank showed depressed semicircle representingthe corrosion process of the system that is the chargetransfer resistance due to the metal corrosion and the doublelayer capacitance of the liquidmetal interface Howeverthe Nyquist spectra of isomers of aminophenol at variousconcentrations showed depressed semicircle The depressedsemicircles in the Nyquist plots were probably due to thesurface heterogeneity or corrosion products of the metalsubstrateThe element at high frequency region is relatedwiththe charge transfer resistance of system elements at low fre-quency regionmay represent adsorption of ions for exampleClminus which is the initial step of anionic or solvent exchangebetween polymers and solution during equilibration in 1MHCl [35ndash37] The Nyquist spectra of blank and isomers ofaminophenol revealed one-time constant behaviour whichis attributed to the charge transfer resistance of corrosionprocess [38] The total impedance in the low frequencyregion for the polymers at higher concentrations seems to bealmost one order of magnitude higher than that displayed

by the blank MS The higher impedance is probably dueto an area effect where the inhibitor is blocking access ofthe aggressive electrolyte to the reactive metal surface [39]The impedance values are given in Table 3 The chargetransfer resistance is increased from 2012Ω cm2 for blanksolution to 13349 4565 and 13895Ω cm2 upon addition of250mgL of PoAP PmAP and PpAP resulting in 85 559and 855 inhibition efficiency respectively The increasein 119877ct value is attributed to the formation of an insulatingprotective film at the metalsolution interface [40 41] Thedouble layer capacitance decreases from 681120583F cmminus2 to 431459 and 429 120583F cmminus2 in the presence of 250mgL of PoAPPmAP and PpAP respectively The initial decrease in 119862dlvalue from blank solution to inhibitor containing electrolyteis due to a decrease in the local dielectric constant whilefurther decrease in 119862dl with increasing concentrations of theinhibitor is due to increase in the thickness of the electricaldouble layer

The enhanced corrosion protection of mild steel byisomers of aminophenol can be explained on the basisof molecular adsorption The polymers inhibit corrosionby controlling both the anodic and cathodic reactions Inacidic solution the polymer molecules exist as protonatedspecies [42]These protonated species adsorb on the cathodicsites of MS and decrease the evolution of hydrogen Theadsorption on anodic sites occurs through long 120587-electronsof aromatic rings (benzenoid and quinoid) and lone pairof electrons of nitrogen atoms which decreases the anodic

International Journal of Electrochemistry 9

0 50 100 150 200 250

0

20

40

60

80

Blank25mgL50mgL

100mgL250mgL500mgL

minusZ998400998400(Ωmiddotc

m2 )

Z998400(Ωmiddotcm2

)

(a)

0 20 40 60 80 100 1200

10

20

30

40

50

Blank25mgL50mgL

100mgL250mgL500mgL

minusZ998400998400(Ωmiddotc

m2 )

Z998400(Ωmiddotcm2

)

(b)

20 40 60 80 100 120 1400

10

20

30

40

50

60

70

Blank25mgL50mgL

100mgL250mgL500mgL

minusZ998400998400(Ωmiddotc

m2 )

Z998400(Ωmiddotcm2

)

(c)

Figure 6 (a) Nyquist plots obtained for mild steel in 1M HCl in the presence and absence of different concentrations of PoAP (b) Nyquistplots obtained for mild steel in 1M HCl in the presence and absence of different concentrations of PmAP (c) Nyquist plots obtained for mildsteel in 1M HCl in the presence and absence of different concentrations of PpAP

dissolution of mild steel [43] It is well known that the specieshaving high molecular weight and bulky structure may covermore area on the active electrode surfaces [44] The highperformance of the PpAP is attributed to the presence of long120587-electrons conjugation quaternary nitrogen atom and thelarger molecular size

4 Conclusion

The isomers of aminophenol were successfully synthesizedby chemical oxidative polymerizationmethod and character-ized by different spectroscopic techniques UV-VIS-NIR andFT-IR suggest the formation of quinoid and benzenoid rings

which confirmed the formation of polymerThe XRD studiesreveal that the morphology of isomers of poly aminophe-nol is partially crystalline and amorphous nature Fromthermal analysis it was found that all the polymers exhibitthree-step decomposition patterns The corrosion behaviourinvestigation the percentage inhibition efficiency of thesepolymers obtained from potentiodynamic polarization andEIS measurements are in good agreement and the corrosioninhibition efficiencies are in the order PpAP gt PoAPgt PmAPPolarization curves demonstrated that the examined poly-mers behave asmixed type inhibitors In these isomers of polyaminophenol the uniform increasing inhibition efficiencyas the function of concentration deals with the adsorption

10 International Journal of Electrochemistry

Table 3 Impedance parameters for mild steel in 1M HCl in thepresence and absence of different concentrations of isomers ofaminophenol

Inhibitorconcentration(mgL)

119862dl(120583Fcm2)

119877ct(Ω cm2) IE ()

PoAPBlank 681 2012 mdash25 548 6481 6950 513 7114 7172100 468 10833 8143250 431 13349 85500 408 20855 9035

PmAPBlank 681 2012 mdash25 622 2520 201750 522 3143 3598100 483 3252 3813250 459 4565 5593500 438 10029 7994

PpAPBlank 681 2012 mdash25 557 49 589450 506 65 6905100 452 1095 8163250 429 13895 8552500 441 115 8250

phenomenon the adsorption of inhibitors on the surface ofMS is indicated by decrease in the double layer capacitanceThe inhibition is due to the adsorption of the inhibitors onthe steel surface and a resultant blocking of active sites Inaddition the 120587-electrons conjugation quaternary nitrogenatom and large size of the polymers also facilitate its strongadsorption on MS which leads to an efficient protection tothe metal in highly corrosive medium The results of thisstudy clearly ascertain that isomers of aminophenol could beconsidered as a candidate for the protection of MS againstcorrosion in an acid environment

Conflict of Interests

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

References

[1] H Ashassi-Sorkhabi and S A Nabavi-Amri ldquoPolarization andimpedance methods in corrosion inhibition study of carbonsteel by amines in petroleum-water mixturesrdquo ElectrochimicaActa vol 47 no 13-14 pp 2239ndash2244 2002

[2] G Avci ldquoCorrosion inhibition of indole-3-acetic acid on mildsteel in 05MHClrdquoColloids and Surfaces A Physicochemical andEngineering Aspects vol 317 no 1ndash3 pp 730ndash736 2008

[3] E A Noor ldquoElectrochemical study for the corrosion inhibitionof mild steel in hydrochloric acid by untreated and treatedcamelrsquos urinerdquo European Journal of Scientific Research vol 20no 3 pp 496ndash507 2008

[4] C A Apostolopoulos D Michalopoulos and P KoutsoukosldquoThe corrosion effects on the structural integrity of reinforcingsteelrdquo Journal of Materials Engineering and Performance vol 17no 4 pp 506ndash516 2008

[5] J Petitjean S Aeiyach J C Lacroix and P C Lacaze ldquoUltra-fastelectropolymerization of pyrrole in aqueous media on oxidiz-able metals in a one-step processrdquo Journal of ElectroanalyticalChemistry vol 478 no 1-2 pp 92ndash100 1999

[6] C A Ferreira S Aeiyach M Delamar and P C LacazeldquoElectropolymerization of pyrrole on iron electrodes Influenceof solvent and electrolyte on the nature of the depositsrdquo Journalof Electroanalytical Chemistry vol 284 no 2 pp 351ndash369 1990

[7] P A Kilmartin L Trier and G A Wright ldquoCorrosion inhi-bition of polyaniline and poly(o-methoxyaniline) on stainlesssteelsrdquo Synthetic Metals vol 131 no 1ndash3 pp 99ndash109 2002

[8] O Abrahao Jr T S P Teixeira J M Madurro A E D HMachado and A G Brito-Madurro ldquoQuantum mechanicalinvestigation of polymer formation from aminophenolsrdquo Jour-nal of Molecular Structure THEOCHEM vol 913 no 1ndash3 pp28ndash37 2009

[9] P Manivel and G Venkatachari ldquoInhibitive effect of p-aminobenzoic acid and its polymer on corrosion of ironin 1 molL HCl solutionrdquo Journal of Materials Science andTechnology vol 22 no 3 pp 301ndash305 2006

[10] PManivel andG Venkatachari ldquoThe inhibitive effect of poly(p-toluidine) on corrosion of iron in 1M HCl solutionsrdquo Journal ofApplied Polymer Science vol 104 no 4 pp 2595ndash2601 2007

[11] S Sathiyanarayanan S K Dhawan D C Trivedi and KBalakrishnan ldquoSoluble conducting poly ethoxy aniline as aninhibitor for iron in HClrdquo Corrosion Science vol 33 no 12 pp1831ndash1841 1992

[12] M C Bernard S Joiret A H-L Goff and P V PhongldquoProtection of iron against corrosion using a polyaniline layerI Polyaniline electrodepositrdquo Journal of the ElectrochemicalSociety vol 148 no 1 pp B12ndashB16 2001

[13] A Guenbour A Kacemi and A Benbachir ldquoCorrosion protec-tion of copper by polyaminophenol filmsrdquo Progress in OrganicCoatings vol 39 no 2ndash4 pp 151ndash155 2000

[14] A Meneguzzi M C Pham C A Ferreira J C Lacroix SAeiyach and P C Lacaze ldquoElectroactive poly(aromatic amine)films deposited onmild steelrdquo Synthetic Metals vol 102 no 1ndash3pp 1390ndash1391 1999

[15] L F DrsquoElia R L Ortız O P Marquez J Marquezand Y Martınez ldquoElectrochemical deposition of poly(o-phenylenediamine) films on type 304 stainless steelrdquo Journalof the Electrochemical Society vol 148 no 4 pp C297ndashC3002001

[16] X-G Li M-R Huang W Duan and Y-L Yang ldquoNovelmultifunctional polymers from aromatic diamines by oxidativepolymerizationsrdquo Chemical Reviews vol 102 no 9 pp 2925ndash3030 2002

[17] D Sazou and M Kourouzidou ldquoElectrochemical synthesisand anticorrosive properties of Nafion-poly(aniline-co-o-aminophenol) coatings on stainless steelrdquo Electrochimica Actavol 54 no 9 pp 2425ndash2433 2009

International Journal of Electrochemistry 11

[18] A P Srikanth T G Sunitha V Raman S Nanjundan and NRajendran ldquoSynthesis characterization and corrosion protec-tion properties of poly(N-(acryloyloxymethyl) benzotriazole-co-glycidyl methacrylate) coatings on mild steelrdquo MaterialsChemistry and Physics vol 103 no 2-3 pp 241ndash247 2007

[19] P Kar N C Pradhan and B Adhikari ldquoA novel route forthe synthesis of processable conducting poly(m-aminophenol)rdquoMaterials Chemistry and Physics vol 111 no 1 pp 59ndash64 2008

[20] A Falcou A Duchene P Hourquebie D Marsacq and ABalland-Longeau ldquoA new chemical polymerization process forsubstituted anilines application to the synthesis of poly(N-alkylanilines) andpoly(o-alkylanilines) and comparison of theirrespective propertiesrdquo SyntheticMetals vol 149 no 2-3 pp 115ndash122 2005

[21] A Elmansouri A Outzourhit A Lachkar et al ldquoInfluence ofthe counter ion on the properties of poly(o-toluidine) thin filmsand their Schottky diodesrdquo SyntheticMetals vol 159 no 3-4 pp292ndash297 2009

[22] P Kar N C Pradhan and B Adhikari ldquoInduced doping bysodium ion in poly(m-aminophenol) through the functionalgroupsrdquo SyntheticMetals vol 160 no 13-14 pp 1524ndash1529 2010

[23] C Chen C Sun and Y Gao ldquoElectrosynthesis of poly(aniline-co-p-aminophenol) having electrochemical properties in a widepH rangerdquo Electrochimica Acta vol 53 no 7 pp 3021ndash30282008

[24] A Ehsani M G Mahjani and M Jafarian ldquoElectrosynthesis ofpoly ortho aminophenol films and nanoparticles a comparativestudyrdquo Synthetic Metals vol 162 no 1-2 pp 199ndash204 2012

[25] C Saravanan S Palaniappan and F Chandezon ldquoSynthesis ofnanoporous conducting polyaniline using ternary surfactantrdquoMaterials Letters vol 62 no 6-7 pp 882ndash885 2008

[26] H Xia and Q Wang ldquoUltrasonic irradiation a novel approachto prepare conductive polyanilinenanocrystalline titaniumoxide compositesrdquo Chemistry of Materials vol 14 no 5 pp2158ndash2165 2002

[27] S Sathiyanarayanan C Marikkannu and N PalaniswamyldquoCorrosion inhibition effect of tetramines for mild steel in 1MHClrdquo Applied Surface Science vol 241 no 3-4 pp 477ndash4842005

[28] C Jeyaprabha S Sathiyanarayanan K L N Phani andG Venkatachari ldquoInvestigation of the inhibitive effect ofpoly(diphenylamine) on corrosion of iron in 05 M H

2

SO4

solutionsrdquo Journal of Electroanalytical Chemistry vol 585 no2 pp 250ndash255 2005

[29] E Hur G Bereket B Duran D Ozdemir and Y SahinldquoElectropolymerization ofm-aminophenol onmild steel and itscorrosion protection effectrdquo Progress in Organic Coatings vol60 no 2 pp 153ndash160 2007

[30] V Shinde A B Gaikwad and P P Patil ldquoSynthesis andcorrosion protection study of poly(o-ethylaniline) coatings oncopperrdquo Surface and Coatings Technology vol 202 no 12 pp2591ndash2602 2008

[31] U Rammelt P T Nguyen and W Plieth ldquoProtection of mildsteel by modification with thin films of polymethylthiophenerdquoElectrochimica Acta vol 46 no 26-27 pp 4251ndash4257 2001

[32] U Rammelt P T Nguyen andW Plieth ldquoCorrosion protectionby ultrathin films of conducting polymersrdquo Electrochimica Actavol 48 no 9 pp 1257ndash1262 2003

[33] A A Hermas ldquoProtection of type 430 stainless steel againstpitting corrosion by ladder conductive polymerrdquo Progress inOrganic Coatings vol 61 no 1 pp 95ndash102 2008

[34] M H Pournaghi-Azar and B Habibi ldquoElectrocatalytic oxida-tion of methanol on poly(phenylenediamines) film palladizedaluminum electrodes modified by Pt micro-particles compar-ison of permselectivity of the films for methanolrdquo Journal ofElectroanalytical Chemistry vol 601 no 1-2 pp 53ndash62 2007

[35] S S A Rehim H H Hassan and M A Amin ldquoCorrosion andcorrosion inhibition of Al and some alloys in sulphate solutionscontaining halide ions investigated by an impedance techniquerdquoApplied Surface Science vol 187 no 3-4 pp 279ndash290 2002

[36] O E Barcia O R Mattos N Pebere and B Tribollet ldquoMass-transport study for the electrodissolution of copper in 1Mhydrochloric acid solution by impedancerdquo Journal of the Elec-trochemical Society vol 140 no 10 pp 2825ndash2833 1993

[37] G Bereket and E Hur ldquoThe corrosion protection ofmild steel by single layered polypyrrole and multilayeredpolypyrrolepoly(5-amino-1-naphthol) coatingsrdquo Progress inOrganic Coatings vol 65 no 1 pp 116ndash124 2009

[38] F Mansfeld ldquoUse of electrochemical impedance spectroscopyfor the study of corrosion protection by polymer coatingsrdquoJournal of Applied Electrochemistry vol 25 no 3 pp 187ndash2021995

[39] A Phanasgaonkar and V S Raja ldquoInfluence of curing temper-ature silica nanoparticles- and cerium on surface morphologyand corrosion behaviour of hybrid silane coatings onmild steelrdquoSurface and Coatings Technology vol 203 no 16 pp 2260ndash22712009

[40] F Bentiss M Traisnel andM Lagrenee ldquoThe substituted 134-oxadiazoles a new class of corrosion inhibitors of mild steel inacidicmediardquoCorrosion Science vol 42 no 1 pp 127ndash146 2000

[41] S Muralidharan K L N Phani S Pitchumani S Ravichan-dran and S V K Iyer ldquoPolyamino-benzoquinone polymers anew class of corrosion inhibitors for mild steelrdquo Journal of theElectrochemical Society vol 142 no 5 pp 1478ndash1483 1995

[42] GAridossM S Kim SM Son J T Kim andY T Jeong ldquoSyn-thesis of poly(p-phenylenediamine- co-o-aminophenol)multi-walled carbon nanotube composites by emulsion polymeriza-tionrdquoPolymers forAdvancedTechnologies vol 21 no 12 pp 881ndash887 2010

[43] M A Quraishi J Rawat and M Ajmal ldquoDithiobiurets a novelclass of acid corrosion inhibitors for mild steelrdquo Journal ofApplied Electrochemistry vol 30 no 6 pp 745ndash751 2000

[44] R C Ayers Jr and N Hackerman ldquoCorrosion inhibition in HClusing methyl pyridinesrdquo Journal of the Elecrochemical Societyvol 110 no 6 pp 507ndash513 1963

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

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