Research Article Effect of Piperidin-4-ones on the Corrosion ...

Research ArticleEffect of Piperidin-4-ones on the Corrosion Inhibition ofMild Steel in 1 N H2SO4

Glory Tharial Xavier1 Brindha Thirumalairaj2 and Mallika Jaganathan2

1Department of Science and Humanities Sri Krishna College of Engineering and Technology CoimbatoreTamil Nadu 641008 India2Department of Chemistry PSG College of Arts and Science Coimbatore Tamil Nadu 641014 India

Correspondence should be addressed to Mallika Jaganathan jmpsgcasgmailcom

Received 20 July 2014 Revised 24 December 2014 Accepted 28 December 2014

Academic Editor Michael I Ojovan

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

The corrosion inhibition of mild steel in 1N sulphuric acid solution by 26-diphenylpiperidin-4-ones with various substituents at 3-and 35-positions (01ndash06) has been tested by weight loss potentiodynamic polarization electrochemical impedance spectroscopicmethods and FTIR and UV absorption spectra The surface morphology of the mild steel specimen has been analyzed by SEMThe effect of temperature (300 to 323 plusmn 1 K) on the corrosion behavior of mild steel in the presence of the inhibitors (01ndash06) wasstudied using weight loss techniques The effect of anions (Clminus Brminus and Iminus) on the corrosion behavior of mild steel in the presenceof the same inhibitors was also studied by weight loss method and the synergism parameters were calculated The adsorptioncharacteristics of the inhibitors have been determined from the results

1 Introduction

Corrosion inhibitors find vast application in the industrialfield as components in acid descaling oil well acidizing acidpickling acid cleaning and so forth Most of the effectiveinhibitors used contain heteroatom such as O N S andmultiple bonds in their molecules through which they areadsorbed on the metal surface It has been observed thatadsorption depends mainly on certain physiochemical prop-erties of the inhibitor group such as functional groups elec-tron density at the donor atom 120587-orbital character and theelectronic structure of themolecule [1ndash8] Several researchersinvestigated the corrosion inhibiting properties of organiccompounds on mild steel in acidic medium [9ndash12] The aimof this work was to investigate the effect of substitution at3- and 35-positions of 26-diphenylpiperidin-4-one on thecorrosion inhibition of mild steel 1 N H

2

SO4

solution Cor-rosion inhibition was investigated using weight loss elec-trochemical impedance spectroscopy (EIS) and potentiody-namic polarization (Tafel) methods and their results werecompared

2 Experimental Details

The variously substituted 26-diphenylpiperidin-4-ones (01ndash06) were prepared via following reported procedures [13 14]Mild steel specimens of the following composition have beenused all over the present investigations (Carbon 007 Sul-phur nil Phosphorous 0008 Manganese 034 remain-ing ferrous)

21 Methods In the gravimetric experiment mild steel spec-imen of the dimensions 25 cm times 1 cm times 01 cm has beenused It was polished using 10 20 30 and 40 emerypapers washed with double distilled water dried and finallydegreased with the acetone In this method previouslyweighed coupon was completely immersed in 100mL 1Nsulphuric acid with and without inhibitor in an open beakerAfter an hour the corrosion product was removed by wash-ing each coupon using double distilled water The washedcoupons were rinsed with acetone and dried in the air beforereweighing From the average weight loss (mean of threereplicates analysis) results the inhibition efficiency (IE) of

Hindawi Publishing CorporationInternational Journal of CorrosionVolume 2015 Article ID 410120 15 pageshttpdxdoiorg1011552015410120

2 International Journal of Corrosion

the inhibitor and the corrosion rate of mild steel (CR) werecalculated using the following equations

Corrosion rate (mmpy) = (876 times 119882)

(119863 times 119860 times 119879)

(1)

where119882 is weight loss in mg119863 is density in mg119860 is area ofexposure in cm2 and 119879 is time in hours

Inhibition efficiency has been determined by using thefollowing relationship

IE () = 119882119900

minus119882119905

119882119900

(2)

119882119900

is weight loss without inhibitor 119882119905

is weight loss withinhibitor

The effects of temperature on the corrosion inhibitionperformance for the variously substituted piperidin-4-ones(01ndash06) were studied in the range of (300 to 323 plusmn 1K)

All the electrochemical measurements were carried outusing a glass cell of 100mL capacity A platinum electrode anda saturated calomel electrode (SCE) were used as counter andreference electrodes respectively The mild steel specimenswere placed in the test solution for 10 minutes before elec-trochemical measurements

The electrochemical impedance measurements were car-ried out over the frequency range of 10 KHz to 001Hz carriedwith AC signed amplitude of the 10mV at the corrosionpotential The measurements were automatically controlledby 119885view software and the impedance diagrams were given asNyquist plots From the plots the electrochemical parameterssuch as double layer capacitance (119862dL) and charge transferresistance (119877ct) were calculated The potentiodynamic polar-ization measurements were made for a potential range ofminus200mV to +200mV with respect to open circuit potentialat a scan rate of 1mVsec From the plot of 119864 versus log 119868the corrosion potential (119864corr) corrosion current (119868corr) wereobtained Tafel slopes 119887

119886

and 119887119888

were obtained in the absenceand presence of inhibitors From the 119868corr values the inhibitionefficiencies were calculated The corrosion rates and inhibi-tion efficiency were obtained from the relationships

Corrosion rate (119862119877

mmpy) = 32 times 119868corr (mAcm2)

timesEquivalent weight

Density

IE =

119868corr(0) minus 119868corr(119894)

119868corr(0)times 100

(3)

where 119868corr(0) is the corrosion current in the absence ofinhibitor and 119868corr(119894) is the corrosion current in the presence ofinhibitor

The surfaces of the corroded and corrosion inhibitedmild steel specimens were examined using scanning electronmicroscopy (JEOL-JSM-35-CF) A Shimadzu FT-IR 8000Spectrophotometer in the 4000ndash400 cmminus1 region using theKBr disc technique was employed to examine the interactionof inhibitors with the metal surface

00000 00005 00010 00015 00020

10

20

30

40

50

60

70

80

010203

040506

Concentration (M)

Inhi

bitio

n effi

cien

cy (

)

Figure 1 Variation of inhibition efficiency with inhibitor (01ndash06)concentration for mild steel in 1N H

2

SO4

at 300 plusmn 1K

3 Results and Discussion

31 Effect of Inhibitor Concentration The corrosion of mildsteel in 1N sulphuric acid solution in the absence and pres-ence of various concentrations (02 times 10minus3 to 2 times 10minus3M) ofinhibitors (01 to 06) was investigated at 300 plusmn 1K for 1-hourimmersion period using weight loss measurements

From the weight loss data plots of inhibition efficiencyversus concentration were made and shown in Figure 1 Theplots confirm that the inhibition efficiency of all the studiedinhibitors (01ndash06) increases with increase in concentration ofthe inhibitor

The extent of inhibition depends on the substituents at 3-position or 35-positions of the 26-diphenylpiperidin-4-oneAt lower concentrations (02 to 1 times 10minus3M) the inhibitionefficiency increases gradually and it almost reaches saturationabove 2 times 10minus3M concentration The order of inhibitionefficiencies of these inhibitors at 300 plusmn 1K is 01 gt 02 gt 06 gt03 gt 05 gt 04 Analysis of the inhibition efficiencies ofinhibitors (01 to 06) reveals that the inhibition efficiencydecreases when it is substituted with various groups (methylethyl isopropyl) at either 3-position of the piperidin-4-one ring or at 35-positions of the piperidin-4-one ringThe observed trend can be explained by considering theconformations of substituted piperidin-4-ones and sterichindrance caused by the substitutes

26-Diphenylpiperidin-4-one exists as an equilibriummixture of both boat and chair conformation [15] whereas 3-alkyl substituted 26-diphenylpiperidin-4-one exists in chairconformation with phenyl and alkyl groups at equatorialpositions [16ndash18] (except in compound (06) where one ofthe C(3)-methyl groups must necessarily be axially oriented)Piperidin-4-ones contain two potential inhibiting groupsnamely the carbonyl group and ring nitrogen [19ndash22] Theinteraction of 26-diphenylpiperidin-4-one (01) with themetal surface could occur through either carbonyl groupor ring nitrogen The less electronegativity of nitrogen thanoxygen favours ring nitrogen to be the inhibiting site

International Journal of Corrosion 3

Sankarapapavinasam et al [21] compared the inhibition effi-ciency of piperidin-4-one and cyclohexanone under identicalconditions They reported that the observed inhibition effi-ciency of piperidin-4-one (65ndash80) was achieved even atvery low concentration of the substrate (10mM) while thatof cyclohexanone (40) was achieved at a much higher con-centration (100mM) The inhibition efficiency of unsubsti-tuted piperidine-4-one is higher than that of cyclohexanoneFurther the inhibition efficiency of 26-diphenylpiperidin-4-one is found to be higher than that of substituted piperidine-4-one This result reveals that the phenyl rings present inthe 26-position which are flanking the ring nitrogen play animportant role in the inhibition of corrosion These phenylgroups are in the equatorial positionThese equatorial phenylgroups of the substituted piperidin-4-ones lie parallel to themild steel surface in chair conformation The interactionbetween the 120587 electrons of phenyl rings and the mild steelsurface prevents the corrosion effectively

The efficiency of 3-methyl-26-diphenylpiperidin-4-one(02) was found to be less than that of 26-diphenylpiperidin-4-one (01) This can be explained as follows In the case ofinhibitor (01) the two phenyl rings at 26 positions are lyingparallel to the metal surface and cause effective interactionwith the metal surface whereas in the case of 3-methyl-26-diphenylpiperidin-4-one (02) the methyl group at the C-3position creates an indirect steric effect known as buttressingeffect It pushes the phenyl rings towards the ring nitrogenthereby changing the orientation of the lone pair of electronson the nitrogen atomThis effect also decreases the 120587 electroninteraction between the phenyl ring and metal surface Byvarying the substituents at C-3 position we can study the but-tressing effect in detail Substitution by ethyl isopropyl 33-dimethyl and 35-dimethyl groups increases the buttressingeffect and decreases the inhibition efficiency In compound(02) methyl (03) ethyl and in (04) isopropyl group is presentAs we move from compound (02) to compound (04) thebulkiness of the group increases so the buttressing effectincreases and hence the inhibition efficiency decreasesGenerally the +I effect of alkyl group increases in the ordermethyl lt ethyl lt isopropyl Isopropyl group has greater +Ieffect than ethyl and methyl and so it is expected to give thehighest inhibition efficiency But in our current investigationinhibitor (04) with isopropyl group shows the least inhibitionefficiency because in this case buttressing effect dominatesover +I effect The inhibition efficiency follows the order 02gt 03 gt 04 In addition to this increase in the degree of chainbranching may also lead to lesser protection efficiency owingto higher steric hindrance [23] Compound (06) with twomethyl groups at C-3 position and compound (05) with onemethyl group each at 3- and 5-position exhibit lesser inhibi-tion efficiency than compound (02) On correlating experi-mental results with molecular structures it can be concludedthat the increase of steric hindrance at C-3 and C-5 positionof substituted piperidin-4-one ring decreased the corrosioninhibiting ability of the studied piperidin-4-ones [24 25]One may expect higher inhibition efficiency for inhibitors(06) and (05) when compared to inhibitor (02) because morenumber of electron releasingmethyl groups is present in theseinhibitors On the contrary inhibitor (02) exhibited higher

efficiencyThe above observation can be explained as followsIf the number of groups in a molecule increases it leads toovercrowding which causes a strain in the molecule whichresults in loss of planarity of the molecule Since the planarityis disturbed the phenyl rings may not have much interactionwith the metal surface That is it may not be able to comecloser with the metal surface to have direct contact whichresults in lesser protection efficiency for (06) and (05) thaninhibitor (02) Moreover the presence of groups which do notact as adsorption centers may not contribute much for theinhibition efficiency of the compound In addition to thisincrease in the degree of chain branching may also lead tolesser protection efficiency owing to higher steric hindrance[23]

32 Effect of Temperature The effect of temperature onthe corrosion inhibition performance of inhibitors (01ndash06)on mild steel in 1N H

2

SO4

is investigated by weight lossmeasurements in the temperature range 300 to 323 plusmn 1K inthe absence and presence of inhibitors (01ndash06) at 04 times 10minus3Mconcentration Table 1 shows the values of corrosion rate sur-face coverage and inhibition efficiency obtained fromweightlossmeasurements at various temperatures (300 to 323plusmn1K)Data in Table 1 suggest that all inhibitors get adsorbedon the mild steel surface at all temperatures studied andcorrosion rate increases with increase in temperature in bothuninhibited and inhibited solutions This can be attributedto the fact that the rate of corrosion reaction increases withincrease in temperature But the rate of corrosion is lessin inhibited solutions compared with uninhibited solutionsDecrease in inhibition efficiencywith increase in temperatureis suggestive of physical adsorption mechanism [26 27] andmay be attributed to increase in the solubility of the protectivefilms and of any reaction products precipitated on the surfaceof mild steel that may otherwise inhibit the corrosion pro-cess As the temperature increases the number of adsorbedmolecules decreases leading to a decrease in the inhibi-tion efficiency A decrease in inhibition efficiency with theincrease in temperature in this case may also be due to weak-ening of physical adsorption [28]

In order to calculate the activation energy (119864119886

) for thecorrosion process Arrhenius equation is used

119862119877

= 119860 exp (minus119864119886

119877119879

) (4)

where 119862119877

is the corrosion rate 119860 is the Arrhenius preexpo-nential factor 119864

119886

is the activation energy for the corrosionprocess 119877 is the universal gas constant and 119879 is the absolutetemperature

The apparent activation energies (119864119886

) at optimum con-centration 04 times 10minus3M of the inhibitors (01ndash06) were deter-mined by linear regression between log119862

119877

and 1119879 andare represented in Figure 2 Plots of log119862

119877

versus 1119879 gavestraight line with slope (minus119864

119886

2303119877) and intercept 119860 Thelinear regression coefficients were close to unity for all theinhibitors analysed The calculated value of activation ener-gies (119864

119886

) and preexponential factors (119860) for the inhibitors arepresented in Table 2 Arrhenius law predicts that corrosion


Table 1 Corrosion parameters for mild steel in 1N H2SO4 inthe absence and presence of optimum concentration of variouslysubstituted piperidin-4-ones (04 times 10minus3 M) obtained from weightloss measurements at different temperatures

Temperature(plusmn1 K) Inhibitor

Inhibitorefficiency

()

Corrosionrate (mmpy)

Surfacecoverage (120579)

300

Blank mdash 5788 mdash(01) 5176 1825 05038(02) 8462 0890 08462(03) 7962 1180 07962(04) 4731 3050 04731(05) 5115 2827 05115(06) 8016 0925 08016

313


318


323


rate increases with the temperature and 119864119886

and 119860 mayvary with temperature in accordance with (4) Inspection ofTable 2 showed that the 119864

119886

value for all the inhibitors studiedwas greater than 20 kJmol in both inhibited and uninhibitedsolutions which revealed that the entire process is controlledby the surface reaction [29]

The value of 119864119886

for the uninhibited solution was foundto be 3496 kJmol and that obtained in the presence ofinhibitors (4007ndash6531 kJmol) for 01ndash06 It is clear that acti-vation energy is higher in inhibited solution than in uninhib-ited solution The increase in the apparent activation energyin the inhibited solution suggests physical adsorption of theinhibitors on themild steel surfaceThe increase in activationenergy can also be attributed to an appreciable decrease inthe adsorption of the inhibitor on the mild steel surfacewith increase in temperature As adsorption decreases moredesorption of inhibitor molecules occurs because these two

010203

040506

3075 3150 3225 3300 3375

135

162

189

216

Blank

log C

R(m

m yminus

1)

1000T (Kminus1)

Figure 2 Arrhenius plots of log119862119877

versus 1119879 for mild steel in 1NH2

SO4

in the absence and presence of inhibitors (01ndash06) at optimumconcentration (04 times 10minus3M)

010203

040506

3075 3150 3225 3300 3375

Blank

1000T (Kminus1)

minus112

minus084

minus056

minus028

log C

RT

(mm

yminus1

Kminus1)

Figure 3Arrhenius plots of log119862119877

119879 versus 1119879 formild steel in 1NH2

SO4


opposite processes are in equilibrium Due to more desorp-tion of inhibitor molecules at higher temperatures the greatersurface area of mild steel comes in contact with aggressiveenvironment resulting in increased corrosion rates withincrease in temperature [30]The very high activation energyin the presence of the inhibitor may be due to the physicaladsorption of the inhibitor species on the mild steel surfaceThis type of inhibitor retards corrosion at ordinary temper-atures but inhibition is diminished at elevated temperature[31]Thus these inhibitors performwell at room temperature

Figure 3 showed the plot of log(119862119877

119879) versus 1119879 forthe corrosion of mild steel in the absence and presenceof inhibitors (01ndash06) in 1N H

2

SO4

In order to calculate


Table 2 Activation parameters 119864119886

Δ119867∘ and Δ119878∘ for the mild steel dissolution in 1N H2SO4 in the absence and presence of variouslysubstituted piperidin-4-ones at optimum concentration (04 times 10minus3 M)

Inhibitor Preexponential factor (g cmminus1 hminus1) 119864119886

(kJmolminus1) 119864119886

minus Δ119867∘ (kJmolminus1) Δ119867

∘ (kJmolminus1) Δ119878∘ (Jmolminus1)

Blank 699 times 107 3496 26 3238 minus4594

(01) 408 times 1012 6531 26 6272 4530

(02) 224 times 1010 5227 26 4969 0571

(03) 567 times 109 4722 26 4464 minus0939

(04) 422 times 1010 4007 26 3749 minus3099

(05) 883 times 108 4217 26 3959 minus2485

(06) 528 times 1010 4714 26 4456 minus0998

Table 3 Activation parameters 119870 and Δ119866∘

ads for the mild steeldissolution in 1N H2SO4 and in the absence and presence ofvariously substituted piperidin-4-ones at optimum concentration(04 times 10minus3 M)

Inhibitors 1198772 Slope 119870 (molminus1) minusΔ119866

∘

ads (kJmolminus1)(01) 100 117 8075 3246(02) 099 120 3501 3037(03) 099 123 1788 2870(04) 100 117 0756 2655(05) 099 143 1414 2811(06) 099 119 2214 2923

the activation parameters like Δ119867∘ and Δ119878∘ for the corrosionprocess transition state equation [24] was used

119862119877

= (119877119879

119873ℎ

) exp(Δ119878∘

119877

) exp(minusΔ119867∘

119877119879

) (5)

where ℎ is Planckrsquos constant 119873 is Avogadrorsquos number 119877 isthe universal gas constant 119879 is the absolute temperatureΔ119878∘ is the entropy of activation and Δ119867

∘ is the enthalpyof activation Plot of log(119862

119877

119879) versus 1119879 gave straightlines with slope (minusΔ119867∘2303119877) and intercept [log(119877119873ℎ) +(Δ119878∘

2303119877)] from which Δ119867∘ and Δ119878∘ were calculated andlisted in Table 2 Inspection of these data revealed that theentropy of activation for the dissolution reaction of mild steelin 1N H

2

SO4

in the presence of all inhibitors (04 times 10minus3M)is higher (3749ndash6272 kJmolminus1) than that in the absence ofinhibitors (3238 kJmolminus1) Positive values of enthalpy of acti-vation (Δ119867∘) in the absence and presence of inhibitor reflectthe endothermic nature of the mild steel dissolution processmeaning that dissolution of steel is difficult It is evidentfrom Table 3 that the value of Δ119867∘ increased in the presenceof the inhibitor compared to the uninhibited solution indi-cating higher protection efficiency This may be attributedto the presence of energy barrier for the reaction hence theprocess of adsorption of inhibitor leads to rise in enthalpy ofthe corrosion process The values of Δ119867∘ and 119864

119886

are nearlythe same and are higher in the presence of the inhibitor Thisindicates that the energy barrier of the corrosion reactionincreased in the presence of the inhibitor without changingthe mechanism of dissolution The value of 119864

119886

is found tobe larger than the corresponding Δ119867∘ value indicating thatthe corrosion processmust involve a gaseous reaction simply

the hydrogen evolution reaction associated with a decreasein the total reaction volume [32 33] Moreover the differencevalue of the 119864

119886

minus Δ119867∘ is found to be 26 kJmol which is

approximately equal to the average value of 119877119879 (263 kJmol)This indicates that the corrosion process is a unimolecularreaction as it is characterized by the following equation

119864119886

minus Δ119867∘

= 119877119879 (6)

This result shows that the inhibitors acted equally on 119864119886

andΔ119867∘On comparing the values of the entropy of activation

(Δ119878∘) in Table 2 it is clear that the positive entropy ofactivation is obtained in the presence of inhibitors whilenegative value (minus4594 Jmolminus1) is observed in the case of free1N H

2

SO4

solution Such variation is concerned with thephenomenon of ordering and disordering of the inhibitormolecules at the electrode surface and could be explained asfollows The adsorption of organic inhibitor molecules fromthe aqueous solution can be regarded as a quasisubstitutionprocess between the organic compounds in the aqueousphase and water molecules at the electrode surface Theadsorption of inhibitors on themild steel surface is accompa-nied by desorption of water molecules from the surfaceThuswhile the adsorption process for the inhibitor is believed tobe exothermic and associated with a decrease in entropy ofthe solute the opposite is true for the solventThe thermody-namic values obtained are the algebraic sumof the adsorptionof organic molecules and desorption of water moleculesHence the gain in entropy is attributed to the increase in sol-vent entropy and to more positive water desorption enthalpyThe positive values of Δ119878∘ also suggest that an increase indisordering takes place on going from reactants to the metalsolution interface [26] which is the driving force for theadsorption of inhibitors onto the mild steel surface

33 Adsorption Isotherm Organic molecules are used toinhibit corrosion as they are adsorbed on the metal solutioninterface The adsorption depends on the nature of theinhibitor its conformation in aqueous solution chemicalcomposition of themedium nature of themetal surface tem-perature and electrochemical potential at the metal solutioninterface Various adsorption isotherms (Henry FrendlichLangmuir Frumkin and Temkin) have been tried for theinhibitors (01ndash06) on the mild steel surface in acidic mediumat room temperature The correlation coefficients (1198772) were


00000 00005 00010 00015 00020

010203

040506

Concentration (M)

0000

0001

0002

0003

0004

C120579

(M)

Figure 4 Langmuir isotherm plots for adsorption of inhibitors (01ndash06) on the mild steel in 1N H

2

SO4

used to determine the best fit For the studied inhibitors bestfit was obtained with Langmuir adsorption isotherm

The Langmuir isotherm is given by the following equa-tion

119862

120579

=1

119870

+ 119862 (7)

where119870 is the equilibrium constant of the adsorption processand119862 is the molar concentration of inhibitorThe plot of119862120579versus 119862 gave straight line (Figure 4) The linear regressioncoefficients (1198772) are almost equal to unityThough the plot of119862120579 versus 119862 is linear the slope obtained is found to deviatefrom unity The deviation of the slope from unity might bedue to interaction among the adsorbed species on the surfaceof the mild steel specimen [34ndash39] or the adsorbate occupiesmore than one adsorption site on the metal surface Similarbehavior was observed by several researchers [40ndash43] andhas suggested the modified Langmuir adsorption isothermLangmuirrsquos adsorption isotherm parameters are presented inTable 3

The values of equilibrium constant 119870 calculated usingLangmuir (8) isotherm are presented in Table 3 A large valueof119870 obtained indicates more efficient adsorption and hencebetter inhibition efficiency The free energy of adsorption(Δ119866∘ads) is related to the adsorption constant (119870) with thefollowing equation

119870 =1

555

exp(minusΔ119866∘

ads119877119879

) (8)

where the value of 555 is the concentration of water in solu-tion expressed in molLminus1 The Δ119866∘ads values obtained fromLangmuir were calculated at room temperature and are listedin Table 3 The large negative values of Δ119866∘ads indicate thespontaneity of the adsorption process and the stability ofthe adsorbed species on the mild steel surface In general

the values of Δ119866∘

ads of the order of minus20 kJmol or lowerindicate a physisorption [44] while those more negative thanminus40 kJmol involve sharing or transfer of electrons from theinhibitor molecules to the metal surface to form a coordinatetype of bond (chemisorption) [45] It is clear fromTable 3 thatthe calculated Δ119866∘ads values are in the range between 2655and 3246 kJmol for H

2

SO4

solution for optimum concen-tration (04 times 10minus3M) of the inhibitor This indicates that theadsorption of these inhibitors on the mild steel surface mayinvolve complex interactions involving both physical adsorp-tion and chemical adsorption [46]

It is well-known that surface charge density and zerocharge potential of metals play an important role in theprocess of the electrostatic adsorption [47] The surfacecharge of the metal is due to the electric field existing atthe metalsolution interface [48] The surface charge canbe defined by the position of 119864corr with respect to therespective potential of zero charge (PZC) 119864

119902=0

When thedifference 119906 = (119864corr minus119864119902=0) is negative the electrode surfaceacquires a negative net charge and the adsorption of cations isfavoured On the contrary the adsorption of anions is favoredwhen you become positive Generally mild steel surface ispositively charged in 1N H

2

SO4

solution [49 50] Howeverthe inhibitors under investigation namely the 26-diphenyl-piperidin-4-ones are protonated (piperidinium cation) inacidic solutions and exist in equilibriumwith the correspond-ing molecular form

The inhibitors studied have Δ119866∘ads value between 2655and 3246 kJmol for 1 N H

2

SO This indicates that theinhibitors adsorb on the mild steel surface through bothmodes of adsorption (physical adsorption and chemicaladsorption) in both acid media The 119870 values increase in theorder of (04) lt (05) lt (03) lt (06) lt (02) lt (01) which is thesame as the order followed by inhibition efficiency obtainedfrom weight loss method

34 Synergistic Effect It is generally accepted that the pres-ence of halide ions in acidic media synergistically increasesthe inhibition efficiency of most of the organic compoundsThe halide ions are able to improve adsorption of the organiccations by forming intermediate bridges between positivelycharged metal surface and the positive end of the organicinhibitor [51] For studying the synergistic inhibitive effectof halide ions an optimum concentration (04 times 10minus3M) ofvariously substituted 26-diphenylpiperidin-4-ones is taken(Scheme 1) and to each of these inhibitors 1 times 10minus3M KClKBrKI is added and the inhibition efficiencies were foundusing weight loss method and the observations are presentedin the Table 4 for 1N H

2

SO4

Analysis of the results indicatesa further reduction in corrosion rate that is the inhibitionefficiency of the inhibitors was enhanced by the addition ofthe anions (1 times 10minus3MKClKBrKI)

As far as the inhibition is concerned it is generallyassumed that the adsorption of the inhibitors at the metalaggressive solution interface is the first step in the inhibitionmechanism [52] The dissolution of mild steel is reduced byeither adsorption of the inhibitor molecule on the mild steelsurface or blocking the active centers available for corrosion


NH

O

r(2)c(6)-Diphenylpiperidin-4-one (01)

NH

O

t(3)-Methyl-r(2)c(6)-diphenylpiperidin-4-one (02)

NH

OCH3

t(3)-Ethyl-r(2)c(6)-diphenylpiperidin-4-one (03)

NH

O

t(3)-Isopropyl-r(2)c(6)-diphenylpiperidin-4-one (04)

NH

O

t(3)t(5)-Dimethyl-r(2)c(6)-diphenylpiperidin-4-one (05)

NH

O

C(3)t(3)-Dimethyl-r(2)c(6)-diphenylpiperidin-4-one (06)

Scheme 1 Structures of variously substituted 26-diphenylpiperidin-4-ones (01ndash06)

Table 4 Inhibition efficiency and synergism parameter of variously substituted 26-diphenylpiperidin-4-ones (04 times 10minus3 M) and KCl KBrand KI (1 times 10minus3 M) systems in 1N H2SO4 solution

InhibitorsWithout KCl KBr and KI

IE ()KCl KBr KI

IE () 119878120579

IE () 119878120579

IE () 119878120579

(02) 5176 6108 114 7238 147 8744 269(03) 3803 5397 124 6610 154 8284 253(04) 2227 3640 112 5020 131 7112 188(05) 3226 4519 114 5816 136 7699 206

It is well-known that the adsorption process is made possibledue to the presence of heteroatoms such as N and O whichare regarded as active adsorption centers As discussed earlierthe inhibitors studied (01ndash06) contain nitrogen oxygen andtwo phenyl rings with 120587 electrons The compound could beadsorbed by the interaction between the lone pair of electronsof the oxygen and nitrogen atoms or the electron rich 120587

systems of the aromatic rings and the mild steel surface Thisprocess as earlier reported by Umoren and Ebenso [53] maybe facilitated by the presence of vacant d-orbital in steelIn addition to the molecular form piperidin-4-ones can bepresent as a protonated species in acidic solutions Generallymild steel surface is positively charged in H

2

SO4

solutionso direct adsorption of a protonated species (piperidiniumcation) on the positively chargedmild steel surface is difficultIn order to facilitate the adsorption of piperidinium cation onthe mild steel surface halide ions are added to the aggressivemedium The added halide ions being negatively chargedare attracted to the positively charged mild steel surface andare adsorbed on metal surface this leads to developmentof excess negative charge at metal solution interface thuslending the mild steel surface negative Now electrostatic

interaction occurs between the positively charged nitrogenatom in the piperidinium cation and negatively charged mildsteel surface [54] resulting in physisorption of the inhibitoron the mild steel surface thereby inhibiting the corrosionprocess From the above discussion it is clear that theaddition of halide ions to the aggressive medium facilitatesthe adsorption of the piperidin-4-ones on the metal surface

From Table 4 it is clear that the synergistic ability of thehalides increased in the order Clminus lt Brminus lt Iminus and similarobservation has been reported by several researchers [55 56]The inhibition efficiency values increase significantly onmov-ing fromClminus to Brminus to Iminus In other words the surface coverage(120579) value increases in the same order This is similar to thefindings of Oguzie et al [41] They have reported that thecorrosion inhibitor synergism results from increased surfacecoverage arising from the ion pair interaction between theorganic cation and the anions The great influence of theiodide ion is often attributed to its large ionic radius highhydrophobicity and low electronegativity compared to theother halide ions In addition the more stable chemisorptionof Iminus ions because of the easy deformability of their electronshells also results in higher inhibition effectThis stabilization


Blank

minus45 minus40 minus35 minus30 minus25 minus20 minus15 minus10 minus05

minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)

04 times 10minus3 M

10 times 10minus3 M

20 times 10minus3 M

log I (Acm2)

Figure 5 Polarization curves for mild steel in 1N H2

SO4

in theabsence and presence of different concentration of inhibitor (01)

may be caused by the interaction between the inhibitor and Iminusions This interaction enhances the inhibition efficiency to aconsiderable extent due to the increase of the surface coveragein the presence of iodide ions According to Hackerman andMakrides [57] the halide ions in general and the iodide ionsin particular prevent the steel dissolution in acid solution by astrong interaction with the metal surface possibly throughchemisorption

The synergism parameter 119878120579

is evaluated using the rela-tionship given by several authors [58ndash60]

119878120579

=1 minus 1205791+2

1 minus 1205791015840

1+2

(9)

where 1205791

is surface coverage by the halide ion 1205792

is surfacecoverage by the inhibitor 120579

1+2

= (1205791

+1205792

)minus (1205791

1205792

) and 12057910158401+2

ismeasured surface coverage for the inhibitor in combinationwith halide ion

The synergism parameters derived from the inhibitionefficiency values obtained from weight loss measurementsare summarized in Table 4 It is evident from Table 4 thatthe 119878120579

values are greater than unity which indicates thatthe improved inhibition efficiency caused by the addition ofhalide ions to the inhibitors is only due to synergistic effectThe highest values of 119878

120579

for Iminus ions confirm the highestsynergistic influence of Iminus ions among halides

35 Potentiodynamic Polarization Measurements Polariza-tion curves for mild steel in 1N H

2

SO4

solutions at roomtemperature without and with addition of different concen-trations of inhibitors (01ndash06) are shown in Figures 5ndash10The anodic and cathodic current potential curves are extrap-olated up to their intersection at the point where corrosioncurrent density (119868corr) and corrosion potential (119864corr) areobtained The electrochemical parameters 119868corr 119864corr anodic

minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)

minus40 minus35 minus30 minus25 minus20 minus15 minus10 minus05

log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)

minus60 minus55 minus50 minus45 minus40 minus35 minus30 minus25 minus20 minus15 minus10 minus05

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M

log I (Acm2)

Figure 7 Polarization curves for mild steel in 1NH2

SO4

in absenceand presence of different concentrations of inhibitor (03)

minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4



Table 5 Polarization parameters for mild steel in 1N H2SO4 in the absence and presence of different concentrations of variously substitutedpiperidin-4-ones

Inhibitor Concentration(10minus3M) minus119864corr (mV vs SCE) 119868corr (mAcm2) 119887

119886

(mVdec) 119887119888

(mVdec) Corrosionrate (mmpy)

Inhibitionefficiency ()

mdash Blank 467 1285 171 250 29224 Nil

(01)04 454 0437 133 250 09925 66031 462 0303 133 225 06882 76442 456 0253 116 225 05751 8032

(02)04 476 0625 170 229 14215 51351 471 0383 155 221 08704 70212 465 0355 145 229 08067 7239

(03)04 472 0804 162 266 18270 37471 467 0603 145 250 13700 53112 479 0433 125 225 09834 6634

(04)04 445 1009 154 291 22947 21461 476 0780 180 266 17731 39312 477 0592 145 250 13450 5396

(05)04 456 0871 133 250 19803 32221 458 0705 155 266 16023 45162 475 0570 145 208 12958 5565

(06)04 476 0723 142 250 16434 43751 463 0512 142 250 11634 60182 469 0387 154 238 08805 6986

minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)

minus55 minus50 minus45 minus40 minus35 minus30 minus25 minus20 minus15 minus10 minus05

log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4


and cathodic Tafel slopes (119887119886

and 119887119888

) obtained from polar-ization measurement are listed in Table 5 The inhibitionefficiency was calculated from the expression

IE () = 119868corr(0) minus 119868corr(119894) times100

119868corr(0) (10)

minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4


where 119868corr(0) and 119868corr(119894) are corrosion current densitiesobtained in the absence and presence of inhibitors respec-tively It is clear from Table 5 and Figures 5ndash10 that the addi-tion of inhibitors to 1NH

2

SO4

solution brings about a changein both the anodic and cathodic Tafel slopes These resultssuggested that the addition of the studied inhibitors reducesthe anodic dissolution and also retards the cathodic hydrogen


Table 6 Impedence parameters for mild steel in 1N H2SO4 in theabsence and presence of optimum concentration (04 times 10minus3 M) ofvariously substituted piperidin-4-ones

Inhibitors 119877ct (Ω cm2) 119862dl (120583F cmminus2) Inhibition

efficiency ()Blank 6548 5944 Nil(01) 1955 2288 6651(02) 1360 3039 5185(03) 1060 3720 3823(05) 0962 4245 3193(06) 1126 3589 4185

evolution reaction indicating that these inhibitors influenceboth cathodic and anodic inhibition reactions Further theaddition of inhibitors decreased the corrosion current density(119868corr) significantly which further decreases with increase inconcentration of the inhibitors (04ndash2 times 10minus3M) and reachesa minimum value at 2 times 10minus3M concentration of inhibitorsAccording to Li et al [61] if the displacement in 119864corr isgt85mV with respect to 119864∘corr (blank) the inhibitor can beviewed as a cathodic or anodic type In our study the max-imum displacement was found to be (12) mV which indicatesthat the inhibitors could be considered as mixed type [62]The behavior of Tafel slopes 119887

119886

and 119887119888

also suggested mixedtype of behavior for the inhibitors Therefore all the studiedinhibitors can be classified as mixed inhibitors for mild steelin 1N H

2

SO4

solution The inhibition efficiency was foundto increase with increase in concentration of the inhibitorsThe values of inhibition efficiency obtained from polariza-tion measurements are almost equal to that obtained fromimpedance analysis and weight loss measurements Theinhibition efficiency values obtained follow the order

(01) gt (02) gt (06) gt (03) gt (05) gt (04)

The above trend is the same as that obtained from weightloss measurement

36 Electrochemical ImpedanceMeasurements Thecorrosionbehavior of mild steel in acidic solution in the absenceand presence of optimum concentration (04 times 10minus3M) ofinhibitors (01ndash06) was investigated by the electrochemicalimpedance spectroscopy method at 300 plusmn 1K and theimpedance parameters 119877ct and 119862dl derived from these inves-tigations are given in Table 6 Nyquist plots of mild steelin inhibiting and uninhibited acidic solutions containingan optimum concentration (04 times 10minus3M) of inhibitors areshown in Figure 11 The semicircular nature of impedancediagrams indicates that the corrosion of mild steel is mainlycontrolled by a charge transfer process and the presenceof the inhibitor does not affect the dissolution mechanismof mild steel [63] The impedance spectra of the Nyquistplots were investigated by fitting the experimental data toa simple equivalent circuit model as shown in Figure 12which includes the solution resistance 119877

119904

and the doublelayer capacitance 119862dl which is placed in parallel to the chargetransfer resistance 119877ct

4 6 8 10 12 14 16 18

Blank 0102

060503

minus2

minus4

minus6

minus8

minus10

minus12

Z998400

real (Ω cm2)

Z998400998400 im

ag(Ω

cm2)

Figure 11 Nyquist plots of mild steel in 1N H2

SO4

in the absenceand presence of optimum concentration of various inhibitors (01ndash06)

Rs

CPE

Rct

Figure 12 Equivalent circuit model for fitting impedance spectra

The charge transfer resistance 119877ct values are calculatedfrom the difference in impedance at low andhigh frequenciesThe 119877ct value is a measure of electron transfer across the mildsteel surface and it is inversely proportional to the corrosionrate The double layer capacitance 119862dl was calculated at thefrequency 119891max at which the imaginary component of theimpedance is maximal using the equation [64]

119862dl =1

2120587119891max119877ct (11)

Analysis of the data presented in Table 6 indicates that themagnitude of 119877ct value increased while that of 119862dl decreasedwith the addition of inhibitors to 1N H

2

SO4

medium atoptimum concentration of inhibitors The decrease in 119862dlvalues results from the adsorption of the inhibitor moleculesat the metal surface The double layer between the chargedmetal surface and the solution is considered as an electricalcapacitor The adsorption of inhibitors on the mild steel sur-face decreases its electrical capacity as they displace the watermolecules and other ions originally adsorbed on the surfaceleading to the formation of a protective adsorption layer onthe electrode surface which increases the thickness of theelectrical double layer The thickness of this protective layer


(119889) is related to 119862dl in accordance with Helmholtz modelgiven by the following equation [27]

119862dl =120576120576119900

119860

119889

(12)

where 120576 is the dielectric constant of the medium and 120576119900

is thepermittivity of free space (8854 times 10minus14 Fcm) and 119860 is theeffective surface area of the electrode From (12) it is clear thatas the thickness of the protective layer that is the film formedby inhibitor molecules increases the 119862dl should decreaseIn our present studies 119862dl value was found to be highestfor uninhibited solution Addition of optimum concentration(04times 10minus3M) of inhibitors to the aggressivemedium is foundto decrease the 119862dl value and also lowest value is obtained forinhibitor 01 with highest inhibition efficiency because in thiscase the inhibitor exists as an equilibrium mixture of bothboat and chair form and boat form of the inhibitor couldadsorb through both CO and NH groups and the parallelorientation of the plain containing the C-2 C-3 C-5 and C-6atoms of piperidone ring screens the mild steel surface fromthe attack of the corrosive media The inhibition efficiencyof inhibitors for the corrosion of mild steel in 1N H

2

SO4

medium is calculated using 119877ct values as follows

IE () = 119877ct(119894) minus 119877ct(0) times100

119877ct(119894) (13)

where119877ct(0) and119877ct(119894) are the charge-transfer resistance valuesin absence and presence of inhibitor respectively The 119877ctvalue was found to be the highest for the inhibitor 01 in bothacid media indicating that the system corrodes slower in 01when compared to others The order of inhibition efficiencyobtained from 119877ct values is as follows

(01) gt (02) gt (06) gt (03) gt (05) gt (04)

The inhibition efficiencies obtained from 119877ct are in goodagreement with those obtained from potentiodynamic andweight loss measurements

37 FTIR Spectral Studies The FTIR spectra of 3-methyl-26-diphenylpiperidin-4-one (02) as well as the adsorbed filmof this inhibitor over mild steel surface were recorded usingShimadzu IRAffinity-1 spectrometerThe FTIR spectra of theinhibitor and the adsorbed film are shown in Figures 13 and14 All the variously substituted piperidin-4-ones involved inthe present investigation have been shown to exist in the chairconformation with alkyl and phenyl groups in equatorialorientations Infrared spectroscopy has been proved to bea valuable tool in the analysis of the stereochemistry ofheterocyclic compounds mainly on the basis of a seriesof bands in the region 2800ndash2600 cmminus1 called Bohlmannbands [65] These bands have also been used in the assess-ment of conformational equilibria in decahydroquinolines[66] and piperidin systems [67 68] Piperidin-4-ones alsoexhibit these bands in the region 3000ndash2800 cmminus1 (Figure 13)and these bands disappear on adsorption through nitrogen(Figure 14) due to the lack of antiperiplanarity with respectto the lone pair of electrons as a result of change in confor-mation [69] The sharp peak around 3296 cmminus1 due to NndashH

5007501000125015001750200025003000350040008 (1cm)

105

1025

100

975

95

925

90

875

85

825

T(

)

329649

302355

297726

287309

280558

231082

225006

169743

149200

144667 137916

133576

131358

127211 122582

119592

114866

95866

92394

8390779181

75227

69151

60085

Figure 13 FTIR spectrum of t(3)-methyl-r(2)c(6)-diphenylpipe-ridin-4-one (02)

322415

320004

317111

298883

288756

281233

229443

173601

149683

136373

108886

81592

80821

75806

74938

61918

61339

59892

58446

57867

5007501000125015001750200025003000350040009

(1cm)

102

100

98

96

94

92

T(

)

Figure 14 FTIR spectrum of corrosion product from mild steelsurface after immersion in 1N H

2

SO4

containing t(3)-methyl-r(2)c(6)-diphenylpiperidin-4-one (02)

200 220 240 260 280 300

00

03

06

09

12

15

18

Abso

rban

ce (a

u)

Wavelength (nm)

12

Figure 15 UV spectra of (2 times 10minus3M) t(3)-methyl-r(2)c(6)-diphen-ylpiperidin-4-one (02) used as inhibitors for mild steel corrosion in1N H

2

SO4

solutions [1] before and [2] after weight loss measure-ments

stretching of the piperidin-4-one (02) has also been shifted tolower frequency region (3224 to 3171 cmminus1) and is broadenedin the IR spectrum of the adsorbed film

The carbonyl stretching frequency of the inhibitor (02)appears at 1697 cmminus1This absorption peak is shifted to higherfrequency (1736 cmminus1) in the spectrum of adsorbed film


(a) (b) (c)

Figure 16 SEM photographs of mild steel sample (a) polished surface (b) after immersion in 1N H2

SO4

solution and (c) in the presence of(2 times 10minus3M) inhibitor (02)

Generally ring carbonyl absorption frequency will be shiftedto higher frequency as the ring becomes more and morestrained [70] similar high frequency shifts of carbonylabsorption are noted in the piperidin-4-one complexes ofcobalt (II) nickel (II) and copper (II) [66]

According to Rengamani et al [1] the high frequencyshift is not attributed to carbonyl participation but due toconformational change of the ring during complex formationthrough ring nitrogen The IR spectrum of the free inhibitor(02) shows no appreciable change in the carbonyl shifts dueto electron releasing groups Hence in the present studies it isreasonable to assume that the high frequency shift of carbonylgroup in the adsorbed film may be due to the ring straincaused by the interaction between ring nitrogen and mildsteel surface A new band is observed in the spectrum of theadsorbed film in the region 520ndash508 cmminus1 and this may beattributed to metal nitrogen bonding

38 UV Absorption Spectra TheUV regions of the electronicspectra of the inhibited solutions before and after immersionof mild steel specimens were recorded using Shimadzu UV-1800 spectrometer and are given in Figure 15 The spectraof the inhibited solution before immersion of the mild steelspecimens show two bands a high intensity band at 224 nmand a low intensity band at 256 nm The low intensity bandmay be assigned to 119899 rarr 120587

lowast transition of carbonyl grouppresent in the inhibitors The high intensity band may be dueto 120587 rarr 120587

lowast transition of the carbonyl group as well as phenylgroupsThe spectra of the inhibited solution after immersionof mild steel plate show very slight shifts compared withthe spectra of inhibited solution before immersion But theabsorption intensity corresponding to the above mentionedbands is high in the inhibited solution aftermild steel immer-sionThismay be attributed to the change in the orientation ofthe phenyl groups of piperidin-4-ones due to adsorption onmild steel surface The change in orientation of the phenylgroups leads to increase in ring strain and this is supportedby FTIR spectrum of the inhibitor The substitutional effectstudied in this chapter also supports the presence of ringstrain

39 Scanning Electron Microscopy (SEM) The discussionpresented above makes it clear that piperidin-4-ones areproved to be good inhibitors for mild steel in 1N H

2

SO4

To confirm the obtained results electron microscope pho-tographs of mild steel specimen were taken before and afterimmersion in 1N H

2

SO4

solution and in the presence of20 times 10minus3M concentration of inhibitor t(3)-methyl-r(2)c(6)-diphenylpiperidin-4-one (02)TheSEMphotographs areshown in Figures 16(a)ndash16(c)

Figure 16(a) illustrates the brightly polished surface of themild steel specimen before immersion in the test solutionwhile Figure 16(b) depicts the effect of 1 N H

2

SO4

solutionson the mild steel specimen after 1-hour immersion It clearlyshows large pits that are caused by the attack of 1 N H

2

SO4

solution On comparing these microphotographs with thosein Figure 16(c) it is evident that in the presence of 20 times10minus3M of inhibitor (02) the surface morphology of the mildsteel specimen has been changed due to the presence ofthe adsorbed layer of inhibitor molecules and the large pitsshown in Figure 16(b) in the absence of inhibitor have beenreduced and the depth of pits has decreased Thus the addi-tion of inhibitor (02) to the aggressive medium has reducedthe corrosion of mild steel specimen in 1N H

2

SO4

solution

4 Conclusion

(1) The various substituted 26-diphenyl-methylpiperi-dine-4-ones (01ndash06) exhibit maximum efficiencytowards the corrosion inhibition of mild steel in 1NH2

SO4

The optimum efficiency of these compoundswas achieved even at very low concentration of theinhibitors (04 times 10minus3M) Thus piperidin-4-ones actas efficient inhibitors Also the order of inhibitionefficiency is as follows 01 gt 02 gt 06 gt 03 gt 05 gt 04 Athigher temperatures the rate of corrosion is less ininhibiting solutions compared with the uninhibitedsolutions

(2) Piperidin-4-ones contain two potential anchoringsites namely the carbonyl group and the ring


nitrogen the results indicate the participation of onlyring nitrogen

(3) The increase in apparent activation energy in theinhibited solution suggests physical adsorption of theinhibitors on the mild steel surface

(4) Positive values of enthalpy of activation (Δ119867∘) in theinhibited solution reflect the endothermic nature ofmild steel dissolution Also the positive values ofentropy of activation (Δ119878∘) suggest that an increase indisordering takes place in metalsolution interface

(5) The values of Δ119866∘ads indicate that the adsorption ofinhibitors on the mild steel surface may involve com-plex interactions involving both physical and chemi-cal adsorptionThe FT-IR and SEM analysis supportsthe formation of protective film on the mild steelsurface

(6) The adsorption on piperidine-4-ones on mild steel in1N H

2

SO4

obeys Langmuir adsorption isotherm(7) The variation of Tafel constants 119887

119886

119887119888

and 119864corr valueswith the increase in concentration of piperidine-4-ones (01ndash06) suggest that these compounds act asmixed type inhibitors

Conflict of Interests

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

References

[1] S Rengamani S Muralidharan M Anbu Kulandainathan andS Venkatakrishna Iyer ldquoInhibiting and accelerating effects ofaminophenols on the corrosion and permeation of hydrogenthrough mild steel in acidic solutionsrdquo Journal of AppliedElectrochemistry vol 24 no 4 pp 355ndash360 1994

[2] S S Abd El-Rehim M A M Ibrahim and K F Khaled ldquo4-Aminoantipyrine as an inhibitor of mild steel corrosion in HClsolutionrdquo Journal of Applied Electrochemistry vol 29 no 5 pp593ndash599 1999

[3] M A Quraishi and D Jamal ldquoInhibition of mild steel corrosionin the presence of fatty acid triazolesrdquo Journal of Applied Electro-chemistry vol 32 no 4 pp 425ndash430 2002

[4] K C Emregul R Kurtaran and O Atakol ldquoAn investigationof chloride-substituted Schiff bases as corrosion inhibitors forsteelrdquo Corrosion Science vol 45 no 12 pp 2803ndash2817 2003

[5] K F Khaled K Babic-Samardzija and N Hackerman ldquoPipe-ridines as corrosion inhibitors for iron in hydrochloric acidrdquoJournal of Applied Electrochemistry vol 34 no 7 pp 697ndash7042004

[6] H-L Wang R-B Liu and J Xin ldquoInhibiting effects of somemercapto-triazole derivatives on the corrosion of mild steel in10MHC1mediumrdquoCorrosion Science vol 46 no 10 pp 2455ndash2466 2004

[7] F Bentiss M Lebrini and M Lagrenee ldquoThermodynamiccharacterization of metal dissolution and inhibitor adsorptionprocesses in mild steel25-bis(n-thienyl)-134-thiadiazoleshydrochloric acid systemrdquo Corrosion Science vol 47 no 12 pp2915ndash2931 2005

[8] S Zor P Dogan and B Yazici ldquoInhibition of acidic corrosionof iron and aluminium by SDBS at different temperaturesrdquoCorrosion Reviews vol 23 no 2-3 pp 217ndash232 2005

[9] M A Quraishi D Jamal and R N Singh ldquoInhibition of mildsteel corrosion in the presence of fatty acid thiosemicarbazidesrdquoCorrosion vol 58 no 3 pp 201ndash207 2002

[10] A Popova M Christov S Raicheva and E Sokolova ldquoAdsorp-tion and inhibitive properties of benzimidazole derivatives inacid mild steel corrosionrdquo Corrosion Science vol 46 no 6 pp1333ndash1350 2004

[11] A Y Musa A A H Kadhum A B Mohamad M S TakriffA R Daud and S K Kamarudin ldquoAdsorption isothermmech-anism of amino organic compounds as mild steel corrosioninhibitors by electrochemical measurement methodrdquo Journal ofCentral South University of Technology vol 17 no 1 pp 34ndash392010

[12] S Vishwanatham and M A Kumar ldquoCorrosion inhibition ofmild steel in binary acid mixturerdquo Corrosion Reviews vol 23no 2-3 pp 181ndash194 2005

[13] M B Balasubramanian and N Padma ldquoStudies on confor-mation-I Preparation and stereochemistry of some 4-piperidi-nolsrdquo Tetrahedron vol 19 no 12 pp 2135ndash2143 1963

[14] C R Noller and V Baliah ldquoThe preparation of some piperidinederivatives by the Mannich reactionrdquo Journal of the AmericanChemical Society vol 70 no 11 pp 3853ndash3855 1948

[15] BVijayan [PhD thesis] AnnamalaiUniversity ChidambaramIndia 1981

[16] M B Balasubramanian and N Padma ldquoStudies on confor-mationmdashI preparation and stereochemistry of some 4-pipe-ridinolsrdquo Tetrahedron vol 19 no 12 pp 2135ndash2143 1963

[17] TM Ikramuddeen [PhD thesis] BharathiarUniversity Coim-batore India 1994

[18] K Selvaraj M Narasimhan and J Mallika ldquoCobalt(II) nitratecomplexes with piperidin-4-onesrdquo Transition Metal Chemistryvol 26 no 1-2 pp 224ndash227 2001

[19] S Muralidharan R Chandrasekar and S V K Iyer ldquoEffect ofpiperidones on hydrogen permeation and corrosion inhibitionof mild steel in acidic solutionsrdquo Proceedings of the IndianAcademy of Sciences Chemical Sciences vol 112 no 2 pp 127ndash136 2000

[20] A N Senthilkumar KTharini andMG Sethuraman ldquoStudieson a few substituted piperidin-4-one oximes as corrosioninhibitor formild steel inHCLrdquo Journal ofMaterials Engineeringand Performance vol 20 no 6 pp 969ndash977 2011

[21] S Sankarapapavinasam F Pushpanaden and M F AhmedldquoPiperidine piperidones and tetrahydrothiopyrones as inhib-itors for the corrosion of copper in H

2

SO4

rdquo Corrosion Sciencevol 32 no 2 pp 193ndash203 1991

[22] A N Senthilkumar K Tharini and M G Sethuraman ldquoCor-rosion inhibitory effect of few piperidin-4-one oximes on mildsteel in hydrochloric acid mediumrdquo Surface Review and Lettersvol 16 no 1 pp 141ndash147 2009

[23] R T Vashi H M Bhajiwala and S A Desai ldquoHexamine ascorrosion inhibitor for zinc in (HNO

3

+ H2

SO4

) binary acidmixturerdquo Der Pharma Chemica vol 5 no 2 pp 237ndash243 2013

[24] K F Khaled K B Samardzija and N Hackerman ldquoPiperidinesas corrosion inhibitors for iron in hydrochloric acidrdquo Journal ofApplied Electrochemistry vol 34 no 7 pp 697ndash704 2004


[25] K Babic-Samardzija K F Khaled and N Hackerman ldquo119873-heterocyclic amines and derivatives as corrosion inhibitors foriron in perchloric acidrdquo Anti-Corrosion Methods and Materialsvol 52 no 1 pp 11ndash21 2005

[26] S K Shukla andE E Ebenso ldquoCorrosion inhibition adsorptionbehavior and thermodynamic properties of streptomycin onmild steel in hydrochloric acid mediumrdquo International Journalof Electrochemical Science vol 6 no 8 pp 3277ndash3291 2011

[27] I Ahamad R Prasad and M A Quraishi ldquoThermodynamicelectrochemical and quantum chemical investigation of someSchiff bases as corrosion inhibitors for mild steel in hydrochlo-ric acid solutionsrdquo Corrosion Science vol 52 no 3 pp 933ndash9422010

[28] I B Obot N O Obi-Egbedi and S A Umoren ldquoAdsorptioncharacteristics and corrosion inhibitive properties of clotrima-zole for aluminium corrosion in hydrochloric acidrdquo Interna-tional Journal of Electrochemical Science vol 4 no 6 pp 863ndash877 2009

[29] A Zarrouk B Hammouti H Zarrok S S Al-Deyab andM Messali ldquoTemperature effect activation energies and ther-modynamic adsorption studies of L-Cysteine Methyl EsterHydrochloride as copper corrosion inhibitor in nitric acid 2MrdquoInternational Journal of Electrochemical Science vol 6 no 12 pp6261ndash6274 2011

[30] C S Venkatachalam S R Rajagopalan and M V C SastryldquoMechanism of inhibition of electrode reactions at high surfacecoveragesmdashIIrdquo Electrochimica Acta vol 26 no 9 pp 1219ndash12241981

[31] A A Khadom A S Yaro A S Altaie and A A H KadumldquoElectrochemical activations and adsorption studies for thecorrosion inhibition of low carbon steel in acidic mediardquoPortugaliae ElectrochimicaActa vol 27 no 6 pp 699ndash712 2009

[32] E A Noor ldquoTemperature effects on the corrosion inhibition ofmild steel in acidic solutions by aqueous extract of fenugreekleavesrdquo International Journal of Electrochemical Science vol 2pp 996ndash1017 2007

[33] M Lebrini F Robert andCRoos ldquoInhibition effect of alkaloidsextract from Annona squamosa plant on the corrosion ofC38 steel in normal hydrochloric acid mediumrdquo InternationalJournal of Electrochemical Science vol 5 no 11 pp 1698ndash17122010

[34] I B Obot S A Umoren and N O Obi-Egbedi ldquoCorrosioninhibition and adsorption behaviour for aluminuim by extractofAningeria robusta in HCl solution synergistic effect of iodideionsrdquo Journal of Materials and Environmental Science vol 2 no1 pp 60ndash71 2011

[35] I M Mejeha A A Uroh K B Okeoma and G A Alozie ldquoTheinhibitive effect of Solanum melongena L leaf extract on thecorrosion of aluminium in tetraoxosulphate (VI) acidrdquo AfricanJournal of Pure and Applied Chemistry vol 4 pp 158ndash165 2010

[36] D Ben Hmamou R Salghi A Zarrouk et al ldquoAlizarin red anefficient inhibitor of C38 steel corrosion in hydrochloric acidrdquoInternational Journal of Electrochemical Science vol 7 no 6 pp5716ndash5733 2012

[37] M A Migahed H M Mohamed and A M Al-Sabagh ldquoCor-rosion inhibition of H-11 type carbon steel in 1 M hydrochloricacid solution by N-propyl amino lauryl amide and its ethoxy-lated derivativesrdquo Materials Chemistry and Physics vol 80 no1 pp 169ndash175 2003

[38] E E Oguzie B N Okolue E E Ebenso G N Onuoha and AI Onuchukwu ldquoEvaluation of the inhibitory effect ofmethyleneblue dye on the corrosion of aluminium in hydrochloric acidrdquoMaterials Chemistry and Physics vol 87 no 2-3 pp 394ndash4012004

[39] E E EbensoNO Eddy andAOOdiongeny ldquoCorrosion inhi-bition and adsorption properties of methocarbamol on mildsteel in acidic mediumrdquo Portugaliae Electrochimica Acta vol 27no 1 pp 13ndash22 2009

[40] R F V Villamil P Corio J C Rubim and S M L AgostinholdquoSodium dodecylsulfate-benzotriazole synergistic effect as aninhibitor of processes on copper mdash chloridric acid interfacesrdquoJournal of Electroanalytical Chemistry vol 535 no 1-2 pp 75ndash83 2002

[41] E E Oguzie Y Li and F H Wang ldquoCorrosion inhibition andadsorption behavior of methionine on mild steel in sulfuricacid and synergistic effect of iodide ionrdquo Journal of Colloid andInterface Science vol 310 no 1 pp 90ndash98 2007

[42] I B Obot and N O Obi-Egbedi ldquoIpomoea involcrata asan ecofriendly inhibitor for aluminium in alkaline mediumrdquoPortugaliae Electrochimica Acta vol 27 no 4 pp 517ndash524 2009

[43] T Umasankareswari and T Jeyaraj ldquoSalicylideneaniline asinhibitor for the corrosion of mild steel in 10 N hydrochloricacidrdquo Journal of Chemical and Pharmaceutical Research vol 4no 7 pp 3414ndash3419 2012

[44] A K Singh and M A Quraishi ldquoInvestigation of the effectof disulfiram on corrosion of mild steel in hydrochloric acidsolutionrdquo Corrosion Science vol 53 no 4 pp 1288ndash1297 2011

[45] M Bouklah B Hammouti M Lagrenee and F Bentiss ldquoTher-modynamic properties of 25-bis(4-methoxyphenyl)-134-oxa-diazole as a corrosion inhibitor for mild steel in normal sulfuricacid mediumrdquo Corrosion Science vol 48 no 9 pp 2831ndash28422006

[46] E E Ebenso I B Obot and L C Murulana ldquoQuinoline andits derivatives as effective corrosion inhibitors for mild steelin acidic mediumrdquo International Journal of ElectrochemicalScience vol 5 no 11 pp 1574ndash1586 2010

[47] M A Amin K F Khaled and S A Fadl-Allah ldquoTesting validityof the tafel extrapolation method for monitoring corrosion ofcold rolled steel inHCl solutionsmdashexperimental and theoreticalstudiesrdquo Corrosion Science vol 52 no 1 pp 140ndash151 2010

[48] A Łukomska and J Sobkowski ldquoPotential of zero charge ofmonocrystalline copper electrodes in perchlorate solutionsrdquoJournal of Electroanalytical Chemistry vol 567 no 1 pp 95ndash1022004

[49] H H Hassan E Abdelghani and M A Amin ldquoInhibition ofmild steel corrosion in hydrochloric acid solution by triazolederivatives Part I Polarization and EIS studiesrdquo ElectrochimicaActa vol 52 no 22 pp 6359ndash6366 2007

[50] M A Amin S S Abd El-Rehim E E F El-Sherbini and RS Bayoumi ldquoThe inhibition of low carbon steel corrosion inhydrochloric acid solutions by succinic acid Part IWeight losspolarization EIS PZC EDX and SEM studiesrdquo ElectrochimicaActa vol 52 no 11 pp 3588ndash3600 2007

[51] E E Ebenso H Alemu S A Umoren and I B Obot ldquoInhi-bition of mild steel corrosion in sulphuric acid using alizarinyellow GG dye and synergistic iodide additiverdquo InternationalJournal of Electrochemical Science vol 3 no 12 pp 1325ndash13392008


[52] L Niu H Zhang F Wei S Wu X Cao and P Liu ldquoCorrosioninhibition of iron in acidic solutions by alkyl quaternary ammo-nium halides correlation between inhibition efficiency andmolecular structurerdquoApplied Surface Science vol 252 no 5 pp1634ndash1642 2005

[53] 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

[54] Y Feng K S Siow W K Teo and A K Hsich ldquoThe synergisticeffects of propargyl alcohol and potassium iodide on the inhi-bition of mild steel in 05M sulfuric acid solutionrdquo CorrosionScience vol 41 no 5 pp 829ndash852 1999

[55] K Parameswari [PhD thesis] Bharathiar University Coimbat-ore India 2006

[56] S A Umoren M M Solomon I I Udosoro and A P UdohldquoSynergistic and antagonistic effects between halide ions andcarboxymethyl cellulose for the corrosion inhibition of mildsteel in sulphuric acid solutionrdquo Cellulose vol 17 no 3 pp 635ndash648 2010

[57] N Hackerman and A C Makrides ldquoInhibition of acid dissolu-tion of metals 1 Some general observationsrdquo Journal of Physicsand Chemistry vol 56 p 707 1955

[58] K Aramaki M Hagiwara and H Nishihara ldquoThe synergisticeffect of anions and the ammonium cation on the inhibition ofiron corrosion in acid solutionrdquo Corrosion Science vol 27 no 5pp 487ndash497 1987

[59] B Sherine A J Abdul Nasser and S Rajendran ldquoInhibitiveaction of hydroquinone Zn2+ system in controlling the cor-rosion of carbon steel in well waterrdquo International Journal ofEngineering Science and Technology vol 2 pp 341ndash357 2010

[60] G Y Elewady A H Elaskalany and A F Molouk ldquoSome 120573-aminoketone derivatives as corrosion inhibitors for nickel inhydrochloric acid solutionrdquo Portugaliae Electrochimica Actavol 26 p 503 2008

[61] W H Li Q He S T Zhang C L Pei and B Hou ldquoSomenew triazole derivatives as inhibitors for mild steel corrosion inacidic mediumrdquo Journal of Applied Electrochemistry vol 38 no3 pp 289ndash295 2008

[62] N Goudarzi M Peikari M Reza Zahiri and H Reza MousavildquoAdsorption and corrosion inhibition behavior of stainless steel316 by aliphatic amine compounds in acidic solutionrdquo Archivesof Metallurgy and Materials vol 57 no 3 pp 845ndash851 2012

[63] S T Arab and A M Al-Turkustani ldquoCorrosion inhibitionof steel in phosphoric acid by phenacyldimethyl sulfoniumbromide and some of its p-substituted derivativesrdquo PortugaliaeElectrochimica Acta vol 24 pp 53ndash69 2006

[64] G Y Elewady ldquoPyrimidine derivatives as corrosion inhibitorsfor carbon-steel in 2Mhydrochloric acid solutionrdquo InternationalJournal of Electrochemical Science vol 3 no 10 pp 1149ndash11612008

[65] F W Vierhapper and E L Eliel ldquoConformational analysis 388-tert-Butyl-trans-decahydroquinolines carbon-13 and protonnuclearmagnetic resonance and infrared spectraThe nitrogen-hydrogen conformational equilibriumrdquo The Journal of OrganicChemistry vol 44 no 7 pp 1081ndash1087 1979

[66] V Venkatachalam K Ramalingam D Natrajan and N Bha-vani ldquobis(2-Aryldecahydroquinolin-4-onedithiocarbamato)-metal(II) complexes a new preparative method and charac-

terization along with 13C and 1H NMR decoupling studiesrdquoSynthesis and Reactivity in Inorganic and Metal-Organic Chem-istry vol 26 no 5 pp 735ndash759 1996

[67] M Golfier Dermination of Configuration by Infrared Spec-troscopy G T Publication Stuttgart Germany 1st edition 1977

[68] T Masamune M Tagasugi and M Matsuki ldquoInfrared-spectralstudies on the orientation of the lone pairs in piperidinederivativesrdquo Bulletin of the Chemical Society of Japan vol 41 no10 pp 2466ndash2472 1968

[69] N Manjula [PhD thesis] Bharathiar University CoimbatoreIndia 2001

[70] R M Silverstein G C Bassler and T C Morill SpectrometricIdentification of Organic Compounds Wiley New York NYUSA 1978

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


the inhibitor and the corrosion rate of mild steel (CR) werecalculated using the following equations

Corrosion rate (mmpy) = (876 times 119882)

(119863 times 119860 times 119879)

(1)

where119882 is weight loss in mg119863 is density in mg119860 is area ofexposure in cm2 and 119879 is time in hours

Inhibition efficiency has been determined by using thefollowing relationship

IE () = 119882119900

minus119882119905

119882119900

(2)

119882119900

is weight loss without inhibitor 119882119905

is weight loss withinhibitor

The effects of temperature on the corrosion inhibitionperformance for the variously substituted piperidin-4-ones(01ndash06) were studied in the range of (300 to 323 plusmn 1K)

All the electrochemical measurements were carried outusing a glass cell of 100mL capacity A platinum electrode anda saturated calomel electrode (SCE) were used as counter andreference electrodes respectively The mild steel specimenswere placed in the test solution for 10 minutes before elec-trochemical measurements

The electrochemical impedance measurements were car-ried out over the frequency range of 10 KHz to 001Hz carriedwith AC signed amplitude of the 10mV at the corrosionpotential The measurements were automatically controlledby 119885view software and the impedance diagrams were given asNyquist plots From the plots the electrochemical parameterssuch as double layer capacitance (119862dL) and charge transferresistance (119877ct) were calculated The potentiodynamic polar-ization measurements were made for a potential range ofminus200mV to +200mV with respect to open circuit potentialat a scan rate of 1mVsec From the plot of 119864 versus log 119868the corrosion potential (119864corr) corrosion current (119868corr) wereobtained Tafel slopes 119887

119886

and 119887119888

were obtained in the absenceand presence of inhibitors From the 119868corr values the inhibitionefficiencies were calculated The corrosion rates and inhibi-tion efficiency were obtained from the relationships

Corrosion rate (119862119877

mmpy) = 32 times 119868corr (mAcm2)

timesEquivalent weight

Density

IE =

119868corr(0) minus 119868corr(119894)

119868corr(0)times 100

(3)

where 119868corr(0) is the corrosion current in the absence ofinhibitor and 119868corr(119894) is the corrosion current in the presence ofinhibitor

The surfaces of the corroded and corrosion inhibitedmild steel specimens were examined using scanning electronmicroscopy (JEOL-JSM-35-CF) A Shimadzu FT-IR 8000Spectrophotometer in the 4000ndash400 cmminus1 region using theKBr disc technique was employed to examine the interactionof inhibitors with the metal surface

00000 00005 00010 00015 00020

10

20

30

40

50

60

70

80

010203

040506

Concentration (M)

Inhi

bitio

n effi

cien

cy (

)

Figure 1 Variation of inhibition efficiency with inhibitor (01ndash06)concentration for mild steel in 1N H

2

SO4

at 300 plusmn 1K

3 Results and Discussion

31 Effect of Inhibitor Concentration The corrosion of mildsteel in 1N sulphuric acid solution in the absence and pres-ence of various concentrations (02 times 10minus3 to 2 times 10minus3M) ofinhibitors (01 to 06) was investigated at 300 plusmn 1K for 1-hourimmersion period using weight loss measurements

From the weight loss data plots of inhibition efficiencyversus concentration were made and shown in Figure 1 Theplots confirm that the inhibition efficiency of all the studiedinhibitors (01ndash06) increases with increase in concentration ofthe inhibitor

The extent of inhibition depends on the substituents at 3-position or 35-positions of the 26-diphenylpiperidin-4-oneAt lower concentrations (02 to 1 times 10minus3M) the inhibitionefficiency increases gradually and it almost reaches saturationabove 2 times 10minus3M concentration The order of inhibitionefficiencies of these inhibitors at 300 plusmn 1K is 01 gt 02 gt 06 gt03 gt 05 gt 04 Analysis of the inhibition efficiencies ofinhibitors (01 to 06) reveals that the inhibition efficiencydecreases when it is substituted with various groups (methylethyl isopropyl) at either 3-position of the piperidin-4-one ring or at 35-positions of the piperidin-4-one ringThe observed trend can be explained by considering theconformations of substituted piperidin-4-ones and sterichindrance caused by the substitutes

26-Diphenylpiperidin-4-one exists as an equilibriummixture of both boat and chair conformation [15] whereas 3-alkyl substituted 26-diphenylpiperidin-4-one exists in chairconformation with phenyl and alkyl groups at equatorialpositions [16ndash18] (except in compound (06) where one ofthe C(3)-methyl groups must necessarily be axially oriented)Piperidin-4-ones contain two potential inhibiting groupsnamely the carbonyl group and ring nitrogen [19ndash22] Theinteraction of 26-diphenylpiperidin-4-one (01) with themetal surface could occur through either carbonyl groupor ring nitrogen The less electronegativity of nitrogen thanoxygen favours ring nitrogen to be the inhibiting site






2

SO4




119862119877

= 119860 exp (minus119864119886

119877119879

) (4)

where 119862119877


119886




119877


119877


119886


119886





Inhibitorefficiency

()



300


313


318


323




119886




010203

040506

3075 3150 3225 3300 3375

135

162

189

216

Blank

log C

R(m

m yminus

1)

1000T (Kminus1)



SO4


010203

040506

3075 3150 3225 3300 3375

Blank

1000T (Kminus1)

minus112

minus084

minus056

minus028

log C

RT

(mm

yminus1

Kminus1)



SO4





2

SO4






(kJmolminus1) 119864119886




(01) 408 times 1012 6531 26 6272 4530

(02) 224 times 1010 5227 26 4969 0571

(03) 567 times 109 4722 26 4464 minus0939

(04) 422 times 1010 4007 26 3749 minus3099

(05) 883 times 108 4217 26 3959 minus2485

(06) 528 times 1010 4714 26 4456 minus0998




∘

ads (kJmolminus1)(01) 100 117 8075 3246(02) 099 120 3501 3037(03) 099 123 1788 2870(04) 100 117 0756 2655(05) 099 143 1414 2811(06) 099 119 2214 2923


119862119877

= (119877119879

119873ℎ

) exp(Δ119878∘

119877


119877119879

) (5)



119877



2

SO4


119886


119886



119886



119864119886

minus Δ119867∘

= 119877119879 (6)




2

SO4




00000 00005 00010 00015 00020

010203

040506

Concentration (M)

0000

0001

0002

0003

0004

C120579

(M)


2

SO4



119862

120579

=1

119870

+ 119862 (7)



119870 =1

555


ads119877119879

) (8)




2

SO4



119902=0


2

SO4



2



2

SO4




NH

O


NH

O


NH

OCH3


NH

O


NH

O


NH

O





IE ()KCl KBr KI

IE () 119878120579

IE () 119878120579

IE () 119878120579

(02) 5176 6108 114 7238 147 8744 269(03) 3803 5397 124 6610 154 8284 253(04) 2227 3640 112 5020 131 7112 188(05) 3226 4519 114 5816 136 7699 206



2

SO4





Blank


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)

04 times 10minus3 M

10 times 10minus3 M

20 times 10minus3 M

log I (Acm2)


SO4





119878120579

=1 minus 1205791+2

1 minus 1205791015840

1+2

(9)

where 1205791



1+2

= (1205791

+1205792

)minus (1205791

1205792

) and 12057910158401+2




120579



2

SO4


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M

log I (Acm2)


SO4


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4





119886

(mVdec) 119887119888



mdash Blank 467 1285 171 250 29224 Nil

(01)04 454 0437 133 250 09925 66031 462 0303 133 225 06882 76442 456 0253 116 225 05751 8032

(02)04 476 0625 170 229 14215 51351 471 0383 155 221 08704 70212 465 0355 145 229 08067 7239

(03)04 472 0804 162 266 18270 37471 467 0603 145 250 13700 53112 479 0433 125 225 09834 6634

(04)04 445 1009 154 291 22947 21461 476 0780 180 266 17731 39312 477 0592 145 250 13450 5396

(05)04 456 0871 133 250 19803 32221 458 0705 155 266 16023 45162 475 0570 145 208 12958 5565

(06)04 476 0723 142 250 16434 43751 463 0512 142 250 11634 60182 469 0387 154 238 08805 6986

minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4



and 119887119888



119868corr(0) (10)

minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4



2

SO4







119886

and 119887119888


2

SO4


(01) gt (02) gt (06) gt (03) gt (05) gt (04)



119904


4 6 8 10 12 14 16 18

Blank 0102

060503

minus2

minus4

minus6

minus8

minus10

minus12

Z998400

real (Ω cm2)

Z998400998400 im

ag(Ω

cm2)


SO4


Rs

CPE

Rct



119862dl =1

2120587119891max119877ct (11)


2

SO4




119862dl =120576120576119900

119860

119889

(12)



2

SO4



119877ct(119894) (13)


(01) gt (02) gt (06) gt (03) gt (05) gt (04)



5007501000125015001750200025003000350040008 (1cm)

105

1025

100

975

95

925

90

875

85

825

T(

)

329649

302355

297726

287309

280558

231082

225006

169743

149200

144667 137916

133576

131358

127211 122582

119592

114866

95866

92394

8390779181

75227

69151

60085


322415

320004

317111

298883

288756

281233

229443

173601

149683

136373

108886

81592

80821

75806

74938

61918

61339

59892

58446

57867

5007501000125015001750200025003000350040009

(1cm)

102

100

98

96

94

92

T(

)


2

SO4


200 220 240 260 280 300

00

03

06

09

12

15

18

Abso

rban

ce (a

u)

Wavelength (nm)

12


2

SO4





(a) (b) (c)


SO4








2

SO4


2

SO4



2

SO4


2

SO4


2

SO4

solution

4 Conclusion


SO4









2

SO4


119886

119887119888




References






















2

SO4




3

+ H2

SO4


































2

SO4



























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials








2

SO4




119862119877

= 119860 exp (minus119864119886

119877119879

) (4)

where 119862119877


119886




119877


119877


119886


119886





Inhibitorefficiency

()



300


313


318


323




119886




010203

040506

3075 3150 3225 3300 3375

135

162

189

216

Blank

log C

R(m

m yminus

1)

1000T (Kminus1)



SO4


010203

040506

3075 3150 3225 3300 3375

Blank

1000T (Kminus1)

minus112

minus084

minus056

minus028

log C

RT

(mm

yminus1

Kminus1)



SO4





2

SO4






(kJmolminus1) 119864119886




(01) 408 times 1012 6531 26 6272 4530

(02) 224 times 1010 5227 26 4969 0571

(03) 567 times 109 4722 26 4464 minus0939

(04) 422 times 1010 4007 26 3749 minus3099

(05) 883 times 108 4217 26 3959 minus2485

(06) 528 times 1010 4714 26 4456 minus0998




∘

ads (kJmolminus1)(01) 100 117 8075 3246(02) 099 120 3501 3037(03) 099 123 1788 2870(04) 100 117 0756 2655(05) 099 143 1414 2811(06) 099 119 2214 2923


119862119877

= (119877119879

119873ℎ

) exp(Δ119878∘

119877


119877119879

) (5)



119877



2

SO4


119886


119886



119886



119864119886

minus Δ119867∘

= 119877119879 (6)




2

SO4




00000 00005 00010 00015 00020

010203

040506

Concentration (M)

0000

0001

0002

0003

0004

C120579

(M)


2

SO4



119862

120579

=1

119870

+ 119862 (7)



119870 =1

555


ads119877119879

) (8)




2

SO4



119902=0


2

SO4



2



2

SO4




NH

O


NH

O


NH

OCH3


NH

O


NH

O


NH

O





IE ()KCl KBr KI

IE () 119878120579

IE () 119878120579

IE () 119878120579

(02) 5176 6108 114 7238 147 8744 269(03) 3803 5397 124 6610 154 8284 253(04) 2227 3640 112 5020 131 7112 188(05) 3226 4519 114 5816 136 7699 206



2

SO4





Blank


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)

04 times 10minus3 M

10 times 10minus3 M

20 times 10minus3 M

log I (Acm2)


SO4





119878120579

=1 minus 1205791+2

1 minus 1205791015840

1+2

(9)

where 1205791



1+2

= (1205791

+1205792

)minus (1205791

1205792

) and 12057910158401+2




120579



2

SO4


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M

log I (Acm2)


SO4


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4





119886

(mVdec) 119887119888



mdash Blank 467 1285 171 250 29224 Nil

(01)04 454 0437 133 250 09925 66031 462 0303 133 225 06882 76442 456 0253 116 225 05751 8032

(02)04 476 0625 170 229 14215 51351 471 0383 155 221 08704 70212 465 0355 145 229 08067 7239

(03)04 472 0804 162 266 18270 37471 467 0603 145 250 13700 53112 479 0433 125 225 09834 6634

(04)04 445 1009 154 291 22947 21461 476 0780 180 266 17731 39312 477 0592 145 250 13450 5396

(05)04 456 0871 133 250 19803 32221 458 0705 155 266 16023 45162 475 0570 145 208 12958 5565

(06)04 476 0723 142 250 16434 43751 463 0512 142 250 11634 60182 469 0387 154 238 08805 6986

minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4



and 119887119888



119868corr(0) (10)

minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4



2

SO4







119886

and 119887119888


2

SO4


(01) gt (02) gt (06) gt (03) gt (05) gt (04)



119904


4 6 8 10 12 14 16 18

Blank 0102

060503

minus2

minus4

minus6

minus8

minus10

minus12

Z998400

real (Ω cm2)

Z998400998400 im

ag(Ω

cm2)


SO4


Rs

CPE

Rct



119862dl =1

2120587119891max119877ct (11)


2

SO4




119862dl =120576120576119900

119860

119889

(12)



2

SO4



119877ct(119894) (13)


(01) gt (02) gt (06) gt (03) gt (05) gt (04)



5007501000125015001750200025003000350040008 (1cm)

105

1025

100

975

95

925

90

875

85

825

T(

)

329649

302355

297726

287309

280558

231082

225006

169743

149200

144667 137916

133576

131358

127211 122582

119592

114866

95866

92394

8390779181

75227

69151

60085


322415

320004

317111

298883

288756

281233

229443

173601

149683

136373

108886

81592

80821

75806

74938

61918

61339

59892

58446

57867

5007501000125015001750200025003000350040009

(1cm)

102

100

98

96

94

92

T(

)


2

SO4


200 220 240 260 280 300

00

03

06

09

12

15

18

Abso

rban

ce (a

u)

Wavelength (nm)

12


2

SO4





(a) (b) (c)


SO4








2

SO4


2

SO4



2

SO4


2

SO4


2

SO4

solution

4 Conclusion


SO4









2

SO4


119886

119887119888




References






















2

SO4




3

+ H2

SO4


































2

SO4



























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






Inhibitorefficiency

()



300


313


318


323




119886




010203

040506

3075 3150 3225 3300 3375

135

162

189

216

Blank

log C

R(m

m yminus

1)

1000T (Kminus1)



SO4


010203

040506

3075 3150 3225 3300 3375

Blank

1000T (Kminus1)

minus112

minus084

minus056

minus028

log C

RT

(mm

yminus1

Kminus1)



SO4





2

SO4






(kJmolminus1) 119864119886




(01) 408 times 1012 6531 26 6272 4530

(02) 224 times 1010 5227 26 4969 0571

(03) 567 times 109 4722 26 4464 minus0939

(04) 422 times 1010 4007 26 3749 minus3099

(05) 883 times 108 4217 26 3959 minus2485

(06) 528 times 1010 4714 26 4456 minus0998




∘

ads (kJmolminus1)(01) 100 117 8075 3246(02) 099 120 3501 3037(03) 099 123 1788 2870(04) 100 117 0756 2655(05) 099 143 1414 2811(06) 099 119 2214 2923


119862119877

= (119877119879

119873ℎ

) exp(Δ119878∘

119877


119877119879

) (5)



119877



2

SO4


119886


119886



119886



119864119886

minus Δ119867∘

= 119877119879 (6)




2

SO4




00000 00005 00010 00015 00020

010203

040506

Concentration (M)

0000

0001

0002

0003

0004

C120579

(M)


2

SO4



119862

120579

=1

119870

+ 119862 (7)



119870 =1

555


ads119877119879

) (8)




2

SO4



119902=0


2

SO4



2



2

SO4




NH

O


NH

O


NH

OCH3


NH

O


NH

O


NH

O





IE ()KCl KBr KI

IE () 119878120579

IE () 119878120579

IE () 119878120579

(02) 5176 6108 114 7238 147 8744 269(03) 3803 5397 124 6610 154 8284 253(04) 2227 3640 112 5020 131 7112 188(05) 3226 4519 114 5816 136 7699 206



2

SO4





Blank


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)

04 times 10minus3 M

10 times 10minus3 M

20 times 10minus3 M

log I (Acm2)


SO4





119878120579

=1 minus 1205791+2

1 minus 1205791015840

1+2

(9)

where 1205791



1+2

= (1205791

+1205792

)minus (1205791

1205792

) and 12057910158401+2




120579



2

SO4


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M

log I (Acm2)


SO4


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4





119886

(mVdec) 119887119888



mdash Blank 467 1285 171 250 29224 Nil

(01)04 454 0437 133 250 09925 66031 462 0303 133 225 06882 76442 456 0253 116 225 05751 8032

(02)04 476 0625 170 229 14215 51351 471 0383 155 221 08704 70212 465 0355 145 229 08067 7239

(03)04 472 0804 162 266 18270 37471 467 0603 145 250 13700 53112 479 0433 125 225 09834 6634

(04)04 445 1009 154 291 22947 21461 476 0780 180 266 17731 39312 477 0592 145 250 13450 5396

(05)04 456 0871 133 250 19803 32221 458 0705 155 266 16023 45162 475 0570 145 208 12958 5565

(06)04 476 0723 142 250 16434 43751 463 0512 142 250 11634 60182 469 0387 154 238 08805 6986

minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4



and 119887119888



119868corr(0) (10)

minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4



2

SO4







119886

and 119887119888


2

SO4


(01) gt (02) gt (06) gt (03) gt (05) gt (04)



119904


4 6 8 10 12 14 16 18

Blank 0102

060503

minus2

minus4

minus6

minus8

minus10

minus12

Z998400

real (Ω cm2)

Z998400998400 im

ag(Ω

cm2)


SO4


Rs

CPE

Rct



119862dl =1

2120587119891max119877ct (11)


2

SO4




119862dl =120576120576119900

119860

119889

(12)



2

SO4



119877ct(119894) (13)


(01) gt (02) gt (06) gt (03) gt (05) gt (04)



5007501000125015001750200025003000350040008 (1cm)

105

1025

100

975

95

925

90

875

85

825

T(

)

329649

302355

297726

287309

280558

231082

225006

169743

149200

144667 137916

133576

131358

127211 122582

119592

114866

95866

92394

8390779181

75227

69151

60085


322415

320004

317111

298883

288756

281233

229443

173601

149683

136373

108886

81592

80821

75806

74938

61918

61339

59892

58446

57867

5007501000125015001750200025003000350040009

(1cm)

102

100

98

96

94

92

T(

)


2

SO4


200 220 240 260 280 300

00

03

06

09

12

15

18

Abso

rban

ce (a

u)

Wavelength (nm)

12


2

SO4





(a) (b) (c)


SO4








2

SO4


2

SO4



2

SO4


2

SO4


2

SO4

solution

4 Conclusion


SO4









2

SO4


119886

119887119888




References






















2

SO4




3

+ H2

SO4


































2

SO4



























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials







(kJmolminus1) 119864119886




(01) 408 times 1012 6531 26 6272 4530

(02) 224 times 1010 5227 26 4969 0571

(03) 567 times 109 4722 26 4464 minus0939

(04) 422 times 1010 4007 26 3749 minus3099

(05) 883 times 108 4217 26 3959 minus2485

(06) 528 times 1010 4714 26 4456 minus0998




∘

ads (kJmolminus1)(01) 100 117 8075 3246(02) 099 120 3501 3037(03) 099 123 1788 2870(04) 100 117 0756 2655(05) 099 143 1414 2811(06) 099 119 2214 2923


119862119877

= (119877119879

119873ℎ

) exp(Δ119878∘

119877


119877119879

) (5)



119877



2

SO4


119886


119886



119886



119864119886

minus Δ119867∘

= 119877119879 (6)




2

SO4




00000 00005 00010 00015 00020

010203

040506

Concentration (M)

0000

0001

0002

0003

0004

C120579

(M)


2

SO4



119862

120579

=1

119870

+ 119862 (7)



119870 =1

555


ads119877119879

) (8)




2

SO4



119902=0


2

SO4



2



2

SO4




NH

O


NH

O


NH

OCH3


NH

O


NH

O


NH

O





IE ()KCl KBr KI

IE () 119878120579

IE () 119878120579

IE () 119878120579

(02) 5176 6108 114 7238 147 8744 269(03) 3803 5397 124 6610 154 8284 253(04) 2227 3640 112 5020 131 7112 188(05) 3226 4519 114 5816 136 7699 206



2

SO4





Blank


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)

04 times 10minus3 M

10 times 10minus3 M

20 times 10minus3 M

log I (Acm2)


SO4





119878120579

=1 minus 1205791+2

1 minus 1205791015840

1+2

(9)

where 1205791



1+2

= (1205791

+1205792

)minus (1205791

1205792

) and 12057910158401+2




120579



2

SO4


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M

log I (Acm2)


SO4


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4





119886

(mVdec) 119887119888



mdash Blank 467 1285 171 250 29224 Nil

(01)04 454 0437 133 250 09925 66031 462 0303 133 225 06882 76442 456 0253 116 225 05751 8032

(02)04 476 0625 170 229 14215 51351 471 0383 155 221 08704 70212 465 0355 145 229 08067 7239

(03)04 472 0804 162 266 18270 37471 467 0603 145 250 13700 53112 479 0433 125 225 09834 6634

(04)04 445 1009 154 291 22947 21461 476 0780 180 266 17731 39312 477 0592 145 250 13450 5396

(05)04 456 0871 133 250 19803 32221 458 0705 155 266 16023 45162 475 0570 145 208 12958 5565

(06)04 476 0723 142 250 16434 43751 463 0512 142 250 11634 60182 469 0387 154 238 08805 6986

minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4



and 119887119888



119868corr(0) (10)

minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4



2

SO4







119886

and 119887119888


2

SO4


(01) gt (02) gt (06) gt (03) gt (05) gt (04)



119904


4 6 8 10 12 14 16 18

Blank 0102

060503

minus2

minus4

minus6

minus8

minus10

minus12

Z998400

real (Ω cm2)

Z998400998400 im

ag(Ω

cm2)


SO4


Rs

CPE

Rct



119862dl =1

2120587119891max119877ct (11)


2

SO4




119862dl =120576120576119900

119860

119889

(12)



2

SO4



119877ct(119894) (13)


(01) gt (02) gt (06) gt (03) gt (05) gt (04)



5007501000125015001750200025003000350040008 (1cm)

105

1025

100

975

95

925

90

875

85

825

T(

)

329649

302355

297726

287309

280558

231082

225006

169743

149200

144667 137916

133576

131358

127211 122582

119592

114866

95866

92394

8390779181

75227

69151

60085


322415

320004

317111

298883

288756

281233

229443

173601

149683

136373

108886

81592

80821

75806

74938

61918

61339

59892

58446

57867

5007501000125015001750200025003000350040009

(1cm)

102

100

98

96

94

92

T(

)


2

SO4


200 220 240 260 280 300

00

03

06

09

12

15

18

Abso

rban

ce (a

u)

Wavelength (nm)

12


2

SO4





(a) (b) (c)


SO4








2

SO4


2

SO4



2

SO4


2

SO4


2

SO4

solution

4 Conclusion


SO4









2

SO4


119886

119887119888




References






















2

SO4




3

+ H2

SO4


































2

SO4



























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




00000 00005 00010 00015 00020

010203

040506

Concentration (M)

0000

0001

0002

0003

0004

C120579

(M)


2

SO4



119862

120579

=1

119870

+ 119862 (7)



119870 =1

555


ads119877119879

) (8)




2

SO4



119902=0


2

SO4



2



2

SO4




NH

O


NH

O


NH

OCH3


NH

O


NH

O


NH

O





IE ()KCl KBr KI

IE () 119878120579

IE () 119878120579

IE () 119878120579

(02) 5176 6108 114 7238 147 8744 269(03) 3803 5397 124 6610 154 8284 253(04) 2227 3640 112 5020 131 7112 188(05) 3226 4519 114 5816 136 7699 206



2

SO4





Blank


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)

04 times 10minus3 M

10 times 10minus3 M

20 times 10minus3 M

log I (Acm2)


SO4





119878120579

=1 minus 1205791+2

1 minus 1205791015840

1+2

(9)

where 1205791



1+2

= (1205791

+1205792

)minus (1205791

1205792

) and 12057910158401+2




120579



2

SO4


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M

log I (Acm2)


SO4


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4





119886

(mVdec) 119887119888



mdash Blank 467 1285 171 250 29224 Nil

(01)04 454 0437 133 250 09925 66031 462 0303 133 225 06882 76442 456 0253 116 225 05751 8032

(02)04 476 0625 170 229 14215 51351 471 0383 155 221 08704 70212 465 0355 145 229 08067 7239

(03)04 472 0804 162 266 18270 37471 467 0603 145 250 13700 53112 479 0433 125 225 09834 6634

(04)04 445 1009 154 291 22947 21461 476 0780 180 266 17731 39312 477 0592 145 250 13450 5396

(05)04 456 0871 133 250 19803 32221 458 0705 155 266 16023 45162 475 0570 145 208 12958 5565

(06)04 476 0723 142 250 16434 43751 463 0512 142 250 11634 60182 469 0387 154 238 08805 6986

minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4



and 119887119888



119868corr(0) (10)

minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4



2

SO4







119886

and 119887119888


2

SO4


(01) gt (02) gt (06) gt (03) gt (05) gt (04)



119904


4 6 8 10 12 14 16 18

Blank 0102

060503

minus2

minus4

minus6

minus8

minus10

minus12

Z998400

real (Ω cm2)

Z998400998400 im

ag(Ω

cm2)


SO4


Rs

CPE

Rct



119862dl =1

2120587119891max119877ct (11)


2

SO4




119862dl =120576120576119900

119860

119889

(12)



2

SO4



119877ct(119894) (13)


(01) gt (02) gt (06) gt (03) gt (05) gt (04)



5007501000125015001750200025003000350040008 (1cm)

105

1025

100

975

95

925

90

875

85

825

T(

)

329649

302355

297726

287309

280558

231082

225006

169743

149200

144667 137916

133576

131358

127211 122582

119592

114866

95866

92394

8390779181

75227

69151

60085


322415

320004

317111

298883

288756

281233

229443

173601

149683

136373

108886

81592

80821

75806

74938

61918

61339

59892

58446

57867

5007501000125015001750200025003000350040009

(1cm)

102

100

98

96

94

92

T(

)


2

SO4


200 220 240 260 280 300

00

03

06

09

12

15

18

Abso

rban

ce (a

u)

Wavelength (nm)

12


2

SO4





(a) (b) (c)


SO4








2

SO4


2

SO4



2

SO4


2

SO4


2

SO4

solution

4 Conclusion


SO4









2

SO4


119886

119887119888




References






















2

SO4




3

+ H2

SO4


































2

SO4



























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




NH

O


NH

O


NH

OCH3


NH

O


NH

O


NH

O





IE ()KCl KBr KI

IE () 119878120579

IE () 119878120579

IE () 119878120579

(02) 5176 6108 114 7238 147 8744 269(03) 3803 5397 124 6610 154 8284 253(04) 2227 3640 112 5020 131 7112 188(05) 3226 4519 114 5816 136 7699 206



2

SO4





Blank


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)

04 times 10minus3 M

10 times 10minus3 M

20 times 10minus3 M

log I (Acm2)


SO4





119878120579

=1 minus 1205791+2

1 minus 1205791015840

1+2

(9)

where 1205791



1+2

= (1205791

+1205792

)minus (1205791

1205792

) and 12057910158401+2




120579



2

SO4


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M

log I (Acm2)


SO4


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4





119886

(mVdec) 119887119888



mdash Blank 467 1285 171 250 29224 Nil

(01)04 454 0437 133 250 09925 66031 462 0303 133 225 06882 76442 456 0253 116 225 05751 8032

(02)04 476 0625 170 229 14215 51351 471 0383 155 221 08704 70212 465 0355 145 229 08067 7239

(03)04 472 0804 162 266 18270 37471 467 0603 145 250 13700 53112 479 0433 125 225 09834 6634

(04)04 445 1009 154 291 22947 21461 476 0780 180 266 17731 39312 477 0592 145 250 13450 5396

(05)04 456 0871 133 250 19803 32221 458 0705 155 266 16023 45162 475 0570 145 208 12958 5565

(06)04 476 0723 142 250 16434 43751 463 0512 142 250 11634 60182 469 0387 154 238 08805 6986

minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4



and 119887119888



119868corr(0) (10)

minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4



2

SO4







119886

and 119887119888


2

SO4


(01) gt (02) gt (06) gt (03) gt (05) gt (04)



119904


4 6 8 10 12 14 16 18

Blank 0102

060503

minus2

minus4

minus6

minus8

minus10

minus12

Z998400

real (Ω cm2)

Z998400998400 im

ag(Ω

cm2)


SO4


Rs

CPE

Rct



119862dl =1

2120587119891max119877ct (11)


2

SO4




119862dl =120576120576119900

119860

119889

(12)



2

SO4



119877ct(119894) (13)


(01) gt (02) gt (06) gt (03) gt (05) gt (04)



5007501000125015001750200025003000350040008 (1cm)

105

1025

100

975

95

925

90

875

85

825

T(

)

329649

302355

297726

287309

280558

231082

225006

169743

149200

144667 137916

133576

131358

127211 122582

119592

114866

95866

92394

8390779181

75227

69151

60085


322415

320004

317111

298883

288756

281233

229443

173601

149683

136373

108886

81592

80821

75806

74938

61918

61339

59892

58446

57867

5007501000125015001750200025003000350040009

(1cm)

102

100

98

96

94

92

T(

)


2

SO4


200 220 240 260 280 300

00

03

06

09

12

15

18

Abso

rban

ce (a

u)

Wavelength (nm)

12


2

SO4





(a) (b) (c)


SO4








2

SO4


2

SO4



2

SO4


2

SO4


2

SO4

solution

4 Conclusion


SO4









2

SO4


119886

119887119888




References






















2

SO4




3

+ H2

SO4


































2

SO4



























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




Blank


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)

04 times 10minus3 M

10 times 10minus3 M

20 times 10minus3 M

log I (Acm2)


SO4





119878120579

=1 minus 1205791+2

1 minus 1205791015840

1+2

(9)

where 1205791



1+2

= (1205791

+1205792

)minus (1205791

1205792

) and 12057910158401+2




120579



2

SO4


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M

log I (Acm2)


SO4


minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4





119886

(mVdec) 119887119888



mdash Blank 467 1285 171 250 29224 Nil

(01)04 454 0437 133 250 09925 66031 462 0303 133 225 06882 76442 456 0253 116 225 05751 8032

(02)04 476 0625 170 229 14215 51351 471 0383 155 221 08704 70212 465 0355 145 229 08067 7239

(03)04 472 0804 162 266 18270 37471 467 0603 145 250 13700 53112 479 0433 125 225 09834 6634

(04)04 445 1009 154 291 22947 21461 476 0780 180 266 17731 39312 477 0592 145 250 13450 5396

(05)04 456 0871 133 250 19803 32221 458 0705 155 266 16023 45162 475 0570 145 208 12958 5565

(06)04 476 0723 142 250 16434 43751 463 0512 142 250 11634 60182 469 0387 154 238 08805 6986

minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4



and 119887119888



119868corr(0) (10)

minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4



2

SO4







119886

and 119887119888


2

SO4


(01) gt (02) gt (06) gt (03) gt (05) gt (04)



119904


4 6 8 10 12 14 16 18

Blank 0102

060503

minus2

minus4

minus6

minus8

minus10

minus12

Z998400

real (Ω cm2)

Z998400998400 im

ag(Ω

cm2)


SO4


Rs

CPE

Rct



119862dl =1

2120587119891max119877ct (11)


2

SO4




119862dl =120576120576119900

119860

119889

(12)



2

SO4



119877ct(119894) (13)


(01) gt (02) gt (06) gt (03) gt (05) gt (04)



5007501000125015001750200025003000350040008 (1cm)

105

1025

100

975

95

925

90

875

85

825

T(

)

329649

302355

297726

287309

280558

231082

225006

169743

149200

144667 137916

133576

131358

127211 122582

119592

114866

95866

92394

8390779181

75227

69151

60085


322415

320004

317111

298883

288756

281233

229443

173601

149683

136373

108886

81592

80821

75806

74938

61918

61339

59892

58446

57867

5007501000125015001750200025003000350040009

(1cm)

102

100

98

96

94

92

T(

)


2

SO4


200 220 240 260 280 300

00

03

06

09

12

15

18

Abso

rban

ce (a

u)

Wavelength (nm)

12


2

SO4





(a) (b) (c)


SO4








2

SO4


2

SO4



2

SO4


2

SO4


2

SO4

solution

4 Conclusion


SO4









2

SO4


119886

119887119888




References






















2

SO4




3

+ H2

SO4


































2

SO4



























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






119886

(mVdec) 119887119888



mdash Blank 467 1285 171 250 29224 Nil

(01)04 454 0437 133 250 09925 66031 462 0303 133 225 06882 76442 456 0253 116 225 05751 8032

(02)04 476 0625 170 229 14215 51351 471 0383 155 221 08704 70212 465 0355 145 229 08067 7239

(03)04 472 0804 162 266 18270 37471 467 0603 145 250 13700 53112 479 0433 125 225 09834 6634

(04)04 445 1009 154 291 22947 21461 476 0780 180 266 17731 39312 477 0592 145 250 13450 5396

(05)04 456 0871 133 250 19803 32221 458 0705 155 266 16023 45162 475 0570 145 208 12958 5565

(06)04 476 0723 142 250 16434 43751 463 0512 142 250 11634 60182 469 0387 154 238 08805 6986

minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4



and 119887119888



119868corr(0) (10)

minus800

minus700

minus600

minus500

minus400

minus300

minus200

E(m

V)


log I (Acm2)

Blank04 times 10

minus3 M10 times 10

minus3 M20 times 10

minus3 M


SO4



2

SO4







119886

and 119887119888


2

SO4


(01) gt (02) gt (06) gt (03) gt (05) gt (04)



119904


4 6 8 10 12 14 16 18

Blank 0102

060503

minus2

minus4

minus6

minus8

minus10

minus12

Z998400

real (Ω cm2)

Z998400998400 im

ag(Ω

cm2)


SO4


Rs

CPE

Rct



119862dl =1

2120587119891max119877ct (11)


2

SO4




119862dl =120576120576119900

119860

119889

(12)



2

SO4



119877ct(119894) (13)


(01) gt (02) gt (06) gt (03) gt (05) gt (04)



5007501000125015001750200025003000350040008 (1cm)

105

1025

100

975

95

925

90

875

85

825

T(

)

329649

302355

297726

287309

280558

231082

225006

169743

149200

144667 137916

133576

131358

127211 122582

119592

114866

95866

92394

8390779181

75227

69151

60085


322415

320004

317111

298883

288756

281233

229443

173601

149683

136373

108886

81592

80821

75806

74938

61918

61339

59892

58446

57867

5007501000125015001750200025003000350040009

(1cm)

102

100

98

96

94

92

T(

)


2

SO4


200 220 240 260 280 300

00

03

06

09

12

15

18

Abso

rban

ce (a

u)

Wavelength (nm)

12


2

SO4





(a) (b) (c)


SO4








2

SO4


2

SO4



2

SO4


2

SO4


2

SO4

solution

4 Conclusion


SO4









2

SO4


119886

119887119888




References






















2

SO4




3

+ H2

SO4


































2

SO4



























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials








119886

and 119887119888


2

SO4


(01) gt (02) gt (06) gt (03) gt (05) gt (04)



119904


4 6 8 10 12 14 16 18

Blank 0102

060503

minus2

minus4

minus6

minus8

minus10

minus12

Z998400

real (Ω cm2)

Z998400998400 im

ag(Ω

cm2)


SO4


Rs

CPE

Rct



119862dl =1

2120587119891max119877ct (11)


2

SO4




119862dl =120576120576119900

119860

119889

(12)



2

SO4



119877ct(119894) (13)


(01) gt (02) gt (06) gt (03) gt (05) gt (04)



5007501000125015001750200025003000350040008 (1cm)

105

1025

100

975

95

925

90

875

85

825

T(

)

329649

302355

297726

287309

280558

231082

225006

169743

149200

144667 137916

133576

131358

127211 122582

119592

114866

95866

92394

8390779181

75227

69151

60085


322415

320004

317111

298883

288756

281233

229443

173601

149683

136373

108886

81592

80821

75806

74938

61918

61339

59892

58446

57867

5007501000125015001750200025003000350040009

(1cm)

102

100

98

96

94

92

T(

)


2

SO4


200 220 240 260 280 300

00

03

06

09

12

15

18

Abso

rban

ce (a

u)

Wavelength (nm)

12


2

SO4





(a) (b) (c)


SO4








2

SO4


2

SO4



2

SO4


2

SO4


2

SO4

solution

4 Conclusion


SO4









2

SO4


119886

119887119888




References






















2

SO4




3

+ H2

SO4


































2

SO4



























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





119862dl =120576120576119900

119860

119889

(12)



2

SO4



119877ct(119894) (13)


(01) gt (02) gt (06) gt (03) gt (05) gt (04)



5007501000125015001750200025003000350040008 (1cm)

105

1025

100

975

95

925

90

875

85

825

T(

)

329649

302355

297726

287309

280558

231082

225006

169743

149200

144667 137916

133576

131358

127211 122582

119592

114866

95866

92394

8390779181

75227

69151

60085


322415

320004

317111

298883

288756

281233

229443

173601

149683

136373

108886

81592

80821

75806

74938

61918

61339

59892

58446

57867

5007501000125015001750200025003000350040009

(1cm)

102

100

98

96

94

92

T(

)


2

SO4


200 220 240 260 280 300

00

03

06

09

12

15

18

Abso

rban

ce (a

u)

Wavelength (nm)

12


2

SO4





(a) (b) (c)


SO4








2

SO4


2

SO4



2

SO4


2

SO4


2

SO4

solution

4 Conclusion


SO4









2

SO4


119886

119887119888




References






















2

SO4




3

+ H2

SO4


































2

SO4



























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a) (b) (c)


SO4








2

SO4


2

SO4



2

SO4


2

SO4


2

SO4

solution

4 Conclusion


SO4









2

SO4


119886

119887119888




References






















2

SO4




3

+ H2

SO4


































2

SO4



























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials









2

SO4


119886

119887119888




References






















2

SO4




3

+ H2

SO4


































2

SO4



























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials


































2

SO4



























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



Research Article Effect of Piperidin-4-ones on the Corrosion ...

Documents

Transcript of Research Article Effect of Piperidin-4-ones on the Corrosion ...