Materials Chemistry and Physics 126 (2011) 983988

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Materials Chemistry and Physics

journa l homepage: www.e lsev ier .com/ lo

The inh atiin acid

Necla CaChemistry Dep

a r t i c l

Article history:Received 10 MReceived in re18 SeptemberAccepted 29 N

Keywords:CorrosionAustenitic staiPolarizationPyrimidine de

henythreurea.O4 hacal imyed aollowthe aest i

1. Introdu

Stainless steel has a wide scope of applications in differentindustries. This type of stainless steel is covered with a protectivelm rich in chromium (oxides/hydroxides) that imparts corrosionresistance to its surface. Amount of chromium prevents the forma-tion of rustacidic solutsevere pittiindustries fwell acidizsteel surfacfumes andinhibitors amaterials inheterocycliphorus, sulin their strThe compoexcellent innitrogen orhigher inhibO

984 N. Caliskan, E. Akbas / Materials Chemistry and Physics 126 (2011) 983988

Scheme 1. Thdiphenyl-1,2,3tolyl-3,4-dihy

0.563; Ni: 8.3trode was coa0.19625 cm2.

2.2. Materials

A mixtur(1.1mmol), (thdrops concentprecipitate wefor one nightDHPM II was ntions [25a]. Thpresent studywere charactemolecular stru

2.3. Test solut

Solvents aFluka, Merck)inhibitor soluttions were choweremixedwwas used.

2.4. Electroch

The potenand electrocheusing a PC confrequency resthree-electrodpolished withand put intoAg/AgCl electrwere referredconstant temp

The workisteady state opical measurempotential waspositive directcurrentsdeterbition efcienequations:

pol (%) =(

i

= i i

i

where i and i

corrosion currcase.

LPR meas10mV arounresistance valu

olarization curves for steel in 0.5M H2SO4 in the absence and presence oft concentrations of DHPM I at 298K.

ed by:

E

i

is then efcesista

=(

R

EIS exat corpacitaplotse Rp ie the i

=(

R

p andR

ults

lariz

entiosencere shed me molecular structure and name of inhibitor used 5-benzoyl-4,6-,4-tetrahydro-2-thiopyrimidin (DHPM I); 5-Benzoyl-6-phenyl-4-p-dropyrimidin-2(1H)-one (DHPM II).

4; Al: 0.0334; Co: 0.0901; Cu: 0.358; Fe: balance. The steel elec-ted with polyester except its bottom surface with surface area of

e of 1,3-diphenyl-1,3-propanedione (1.6mmol), aryl aldehydeio)urea (1.1mmol) and 20ml of glacial acetic acid containing a fewrated hydrochloric acid was heated under reux for 8h. After there ltered off, the solution was held at the room temperature 25 Cand recrystallized from suitable solvents. The synthesis method ofot able to be reached, in spite of it is available the theoretical calcula-erefore, it has been thought that the synthesis method applied in theis different [25b]. DHPM I synthesized according to Ref. [26]. DHPMsrized on the basis of their spectral data and elementary analyses. Thectures of DHPM I and II are shown in Scheme 1.

ions

nd material synthesis chemicals are commercially available (Aldrich,and were used without further purication. 0.5mol dm3 H2SO4 andions were prepared using double distilled water. Inhibitor concentra-sen as 1104, 5104, 1103 and 2103 mol dm3. Solutions

ith amagnetic stirrer. For eachexperiment, a freshlyprepared solution

emical measurements

tiodynamic polarization curves, linear polarization resistance (LPR)mical impedance spectroscopy (EIS) measurements were carried outtrolled Iviumstat PGZ 301 system with an electrochemical system

ponse analyser (FRA). A double-wall one-compartment cell with ae conguration was used. Before each experiment, the electrode was1200 grit emery paper, washed thoroughly with bidistilled water

the cell. A platinum rod was used as the counter electrode and aode served as a reference electrode. All the potentials reported hereto the Ag/AgCl. The cell was a water-jacketed version, connected to aerature circulator at 298K.ng electrode was immersed in test solution for 30min to establishen circuit potential (Eocp). After measuring the Eocp, the electrochem-ents were performed. The potential sweep rate was 1mVs1. Thescanned in the negative direction from Ecorr and subsequently in theion. Inhibition efciencies, pol (%), can be calculated from corrosionminedusing theTafel extrapolationmethod [27]. Thepercentage inhi-

Fig. 1. Pdifferen

calculat

Rp = A ddwhere Ainhibitioization r

Rp (%)

The0.01Hzlayer caNyquist

Sinccalculat

EIS (%)

whereR

3. Res

3.1. Po

Potthe ab298K ainhibitcy, , and the surface coverage, , were calculated from the following

ii

) 100

are the corrosion current densities without and with inhibitor. Theents were determined from the intersection of the Tafel plots for each

urements were carried out by recording the electrode potentiald open circuit potential with 0.1mVs1 scan rate [27]. Polarizationes were obtained from the slope of the potentialcurrent lines and

Fig. 2. Polarizdifferent concsurface area of the electrode. The Rp values were used to calculate theiencies (Rp, %), using the following equation. Rp and Rp are the polar-nces in the presence and absence of the organic additive, respectively.

p RpRp

) 100

periments were conducted in the frequency range of 40000Hz torosion potential by applying 5mV sine wave AC voltage. The doublence (Cdl) and the polarization resistance (Rp) were calculated from[27,28].s inversely proportional to the corrosion current it can be used tonhibitor efciency (EIS, %), from the relation:

p RpRp

) 100

p are uninhibited and inhibited polarization resistances, respectively.

and discussion

ation measurements

dynamic polarization curves of steel in 0.5M H2SO4 inand presence of various concentrations of DHPMs at

own in Figs. 1 and 2. Anodic and cathodic currentswereore effectively with an increase in the concentration ofation curves for steel in 0.5M H2SO4 in the absence and presence ofentrations of DHPM II at 298K.

N. Caliskan, E. Akbas / Materials Chemistry and Physics 126 (2011) 983988 985

Table 1Corrosion parameters for steel in 0.5M H2SO4 in the absence and presence of DHPM I and II.

DHPMs Inhibitor concentration (mol dm3) Ecorr (V) icorr (mAcm2) a (mVdec1) c (mVdec1) pol (%) a

I None 0.393 0.0465 93 85 62 89 73 0.7368 101 87 0.8749 136 88 0.8842 176 90 0.90

II 93 85 51 110 50 0.5055 105 59 0.5957 103 78 0.7858 100 83 0.83

a Degree of

the inhibitothan that of

These redissolution

The corrcurrent denpotential (Edegrees ()in Table 1. TII.

In acidicsage of methe cathodihydrogen gthe anodicthe anodic Tsmaller thathis indicatues of the cAlso corrospound canwhen the cSince the la(Table 1), itsidered as acompoundstion of steelDHPM II is ation of comdissolutionlution reactconcentratition effectby the natuthe organic

Thesurfaemerges atface chargecharge (PZCspondingmthe surfacethe metal suface chargeslightly negof the acidthe hydrogeacid. The mmedia usinefciency thcontinuingsteel in hyd

as re 2

steeosiormelutiofrom

zoyltautocomponizyr), Chighsencthe iPM IgionII inatom

intered thof su.

near

arizaing ior efe adive ss ord

ectro

provof thgatio]. Ny1104 0.339 0.01245104 0.320 0.00621103 0.296 0.00572103 0.259 0.0046None 0.393 0.04651104 0.356 0.02345104 0.343 0.01891103 0.341 0.01022103 0.340 0.0081

surface coverage.

rs, but the reduction in the anodic current was greaterthe cathodic current.

sults showed that theadditionofDHPMsreduces anodicand also retards the hydrogen evolution reaction.esponding electrochemical parameters, i.e., corrosionsity (icorr), Tafel slope constants (a and c), corrosioncorr), inhibition efciency, (%) and surface coveragevalues were calculated from these curves and are givenhe inhibition efciency follows order, DHPM I>DHPM

solutions, the anodic reaction of corrosion is the pas-tal ions from the metal surface into the solution, andc reaction is the discharge of hydrogen ions to produceas or to reduce oxygen. The inhibitor may affect eitheror the cathodic reaction, or both [29,30]. The values ofafel constant, a, calculated for inhibited solutions are

n obtained for the uninhibited in H2SO4 concentration;es that the inhibitors affected anodic reactions. The val-athodic Tafel constant, c, showed an opposite trend.ion potentials shifted to the positive direction. A com-be classied as an anodic- or a cathodic-type inhibitorhange in the Ecorr value is larger than 85mV [30,31].rgest displacement exhibited by DHPM I was 134mVmay be concluded that this molecule should be con-n anodic-type inhibitor, meaning that the addition ofto a 0.5M H2SO4 solution reduces the anodic dissolu-. The change of Ecorr was observed 53mV; therefore themixed-type inhibitor (Table 1), meaning that the addi-pounds to a 0.5M H2SO4 solution reduces the anodicof steel and also retards the cathodic hydrogen evo-ion. The corrosion inhibition increased with inhibitoron. Particularly, the DHPM I exhibited higher inhibi-than DHPM II. The process of inhibition is inuencedre and the charge of the metal, chemical structure ofinhibitor and the type of electrolyte [32].ce chargeof themetal isdue to theelectricaleldwhichthe interface by immersion in the electrolyte. This sur-can be determined by comparing the potential of zero) and the stationary potential of the metal in the corre-edium [4]. As PZC corresponds to the potential atwhich

It won theat corrplex fothe soorbed[34].

Benof thein thedeprotC O (p

Thethe preNH infor DHC S reDHPMthan Omightadsorbatomssurface

3.2. Li

Polincreasinhibitthat ththe actfollow

3.3. El

EISmanceinvestials [35of electrode is charge-free, at the corrosion potentialrface can be positively or negatively charged. The sur-of immersed iron in the H2SO4 solution is positive orative compared with PZC [4,32]. Corrosion mechanismdissolution of stainless steel is dependent not only onn ion concentration but also on the counter ion of theajority of corrosion inhibition studies of steel in H2SO4g different organic compounds showed less inhibitionan inHClmedium [33]. Therefore some studies are also

in our laboratory onpyrimidine compoundson stainlessrochloric acid. Scheme 2. Sc

tautomerisatioported [34] that SO4 has a low tendency to adsorbl surface. The steel surface is more positively chargedn potential. Hence the concentration of surface com-d is not sufcient to cover the electrode surface fromn or the complex is not so stable that it is des-the surface. In both cases, the corrosion rate is high

groupmaynotbeeffective as adsorption center becausemerisation benzoyl group and pyrimidine ring systemounds (Scheme 2). Moreover, the ligands might not be

e in acid solutions, it means that only three regions ofS and NH are responsible for interaction (Scheme 1).

inhibition effect of the DHPM I could be explained bye of the sulfur atom. The functional groups, such as C S,nhibitormolecules are superior as theadsorptioncenter. Due to the high nucleophilic character of S atom theis convenient for adsorption. The functional groups ofwhich the nucleophilic character of N(3) atom is higher, are the regions of C O (pyr), NH and the last one

act with steel. As explained above the compounds arerough strong interactions between negatively chargedlfur, oxygen or nitrogen and positively charged steel

polarization measurements

tion resistance and inhibitor efciency increases withnhibitor concentration. Polarization resistance and theciency Rp (%) values are given in Table 2 indicatedsorption of the inhibitor on the steel surface blockedites and inhibit corrosion [27]. The inhibition efciencyer, DHPM I>DHPM II.

chemical impedance spectroscopy measurements (EIS)

ides a rapid and convenient way to evaluate the perfor-e organic-coated metals and has been widely used forn of protective properties of organic inhibitors on met-quist plots of steel in 0.5M H2SO4 solution in absencehematic representation of studied pyrimidine compounds belong ton.

986 N. Caliskan, E. Akbas / Materials Chemistry and Physics 126 (2011) 983988

Table 2Polarization resistances and inhibition efciencies obtained from the linear polar-ization method for steel in 0.5M H2SO4.

DHPMs Inhibitor concentration (mol dm3) Ecorr (V) Rp ( cm2) RpI None 0.396 87.52

1104 0.340 244.92 645104 0.320 607.30 861103 0.300 750.69 882103 0.266 858.12 90

II None 0.396 87.52 1104 0.363 149.26 415104 0.351 185.54 531103 0.345 344.43 752103 0.340 458.22 81

Fig. 3. Nyquisconcentration

and presenare given in

It could bsemicircleinhibitor us

The diainhibitors tnounced wadsorptionsemicirclestheNyquistand other in

Fig. 4. Nyquisdifferent conc

Fig. 5. Nyquist diagrams for steel in 0.5M H2SO4 in the absence and presence ofdifferent concentrations of DHPM II at 298K.

eters such as charge transfer resistance of the corrosion reaction(Rp) and thethe analysiresistance,

anceimumNyqun:

1fma

lculaNyqoryted ties oft diagrams for steel in 0.5M H2SO4 of DHPMs in 2103 mol dm3at 298K.

ce of various concentrations of pyrimidine derivativesFigs. 35.

impedat maxof therelatio

Cdl = 2The ca

Thethe theattribugeneite noticed from the data of Figs. 35 that the impedancesize depends on the type and concentration of theed.meter of semicircle increased after the addition ofo the aggressive solution. This increase was more pro-ith increasing inhibitor concentration which indicatesof inhibitor molecules on the metal surface [36] Theare observed to be depressed into the Z (reel axis) ofplot as a result of the roughness of the electrode surfacehomogeneities of the solid surface [37,38]. The param-

t diagrams for steel in 0.5M H2SO4 in the absence and presence ofentrations of DHPM I at 298K.

side, electrotion side it ielectrons, thquite a largeIt can be ob(Rp) increastwo inhibitthe formati[32]. The thin inhibitor

Also, thein the presdecrease innessof thed

Table 3Polarization reusing the imp

DHPMs Ic(

I N1512

II N1512capacity of the double layer (Cdl) can be deduced froms of the Nyquist diagram [27,38]. The charge transferRp, values could be calculated from the difference inat lower and higher frequencies. Cdl can be determined

frequency (fmax), at which the imaginary componentist plot is maximum, and calculated using the follow

x 1

Rp

ted impedance parameters are given in Table 3.uist plots are not perfect semicircles as expected fromof EIS. The deviation from ideal semicircle is generallyo the frequency dispersion as well as to the inhomo-surface and mass transport resistant [36]. On the metalns control the charge distribution whereas on the solu-s controlled by ions. Since ions are much larger than theeequivalent ions to the chargeon themetalwill occupyvolumeon the solution side of the double layer [39,40].

tained from Table 3 that, the charge transfer resistancees as the concentration of the inhibitor increases for theors studied. The increase in Rp values is attributed toon of protective lm on the electrode/solution interfaceickness of this protective layer increases with increaseconcentration.capacitance of electrical double layer (Cdl) decreases

ence of inhibitors. This decrease in Cdl results from alocal dielectric constant and/or an increase in the thick-ouble layer [41], suggesting thatDHPMs inhibit the ironsistance and inhibitor efciencies for steel in 0.5M H2SO4 obtainededance method.

nhibitoroncentrationmoldm3)

Rp ( cm22) Cdl (F cm2) fmax EIS (%)

one 65.78 235.0 10.3 104 252.82 67.0 9.4 74104 693.44 31.4 7.3 91103 721.94 18.1 12.2 91103 812.21 16.1 12.2 92one 65.78 235.0 10.3 104 121.95 113.5 11.5 46104 179.03 90.75 9.8 63103 344.49 53.74 8.6 81103 445.22 45.27 7.9 85

N. Caliskan, E. Akbas / Materials Chemistry and Physics 126 (2011) 983988 987

corrosion by adsorption at steel/acid interface. A low capacitancemay result if water molecules at the electrode interface are largelyreplaced by organic inhibitor molecules through adsorption.

The inhibition efciency follows the order: DHPM I>DHPM II.

3.4. Adsorp

The adsmolecules a

Org(sol) +nHwhere Org(tion and adnumber ofwIt is generaelectrode/soanism of thadsorptionorganic moattraction binteractionmetal, (3) inbination ofcharged nalishing a phWaals forceform a donprecipitatio

It is esseisotherm thinhibitor antested in oradsorptionsolution. Lawith an aveLangmuir aequation:

C(inh)

= 1K(a

where isis the inhibequilibriumrepresentatdynamic po

The valureciprocal ofound as 10and DHPM

The stansteel surfac

Gads = RThe standaor less negbetween chcal adsorptcharge sharsurface to fo[37].

The calcfound 28respectivelythe potentivalue of G

angmns of

e vales o

is lesn therimbiniy user remtionpplieosionDRe itn po

ln m

maxto ai pot

ln(

equation, Cinh is the concentration of the inhibitor. R is gasnt (kJ K1 mol1) and T is temperature (K).application of the DR isotherm model is depicted in Fig. 7,shows that a plots of ln versus 2. Application of the DR

ubininRadushkevichadsorption isothermmodel for stainless steel in0.5Montaining DHPMs.tion isotherm

orption process consists of the replacement of watert a corroding interface according to following process.

2O(ads) Org(ads) +nH2O(sol)sol) and Org(ads) are the organic molecules in the solu-sorbed on the metal surface, respectively, and n is theatermolecules replaced by the organicmolecules [36].

lly assumed that the adsorption of the inhibitor at thelution interface is the rst step in the action mech-e inhibitors in aggressive acid media. Four types ofmay take place in the inhibiting phenomena involvinglecules at the metal/solution interface: (1) electrostaticetween charged molecules and the charged metal, (2)of unshared electron pairs in the molecule with theteraction of electrons with the metal and (4) a com-the above [42]. Adsorption results from the polar orture of the organic molecule/ionic species rst estab-ysisorbed surface lm (through electrostatic or van ders) that may stabilize further through chemisorption toor type bond. Other mechanisms are concerned withn, complexation, etc. [43].ntial to knowthemodeof adsorptionand theadsorptionat can give important information on the interaction ofdmetal surface [27]. Several adsorption isothermswereder to nd the best suitable adsorption isotherm forof DHPMs on the stainless steel surface in 0.5M H2SO4ngmuir adsorption isothermswere foundmore suitablerage correlation coefcient of 0.9999 forDHPMs (Fig. 6).dsorption isotherm can be expressed by the following

ds)+ C(inh)

the degree of coverage on the metal surface, C(inh)itor concentration in the electrolyte and K(ads) is theconstant for the adsorptiondesorption process. A

ive Langmuir adsorption isotherm using the potentio-larization data is given in Fig. 6.es of equilibrium constant, Kads calculated from thef the intercept of isotherm line. The values of K are104 and 5104 dm3 mol1 for compound DHPM I

II successively.dard free energy of adsorption of inhibitors (Gads) one can be evaluated with the following equation:

T ln K

rd free energy of adsorption values of 20kJmol1ative are associated with an electrostatic interactionarged molecules and charged metal surface (physi-

ion); those of 40kJmol1 or more negative involvesing or transfer from the inhibitormolecules to themetalrm a co-ordinate covalent bond (chemical adsorption)

ulated standard free energy of adsorption values were.81 and 26.81kJmol1 for DHPM I and DHPM II,. (Thermodynamic parameters were determined from

odynamic polarization measurements.) The decreasingads reects the increasing adsorption capability. The

Fig. 6. Lcentratio

negativmolecuGadsbetwee

ExpintoDuinitialltion foadsorphave aof corr

Thebecaussorptio

ln =whererelatedPolany

= RT

In thisconsta

Thewhich

Fig. 7. DH2SO4 cuir adsorption plot for steel in 0.5M H2SO4 containing different con-DHPM I and DHPM II.

lues of Gads showed that the adsorption of inhibitorn themetal surface is spontaneous [27,39]. The value ofs than 40kJmol1, indicating electrostatic interactione charged metal surface, i.e., physical adsorption [44].ental results obtained in this study were further ttednRadushkevich isothermmodel (DR). Thismodelwasd to distinguish betweenphysical and chemical adsorp-oval of some pollutants from aqueous solutions by

on various adsorbents [45]. Recently, Solomonet al. [46]d thismodel in explaining themechanismof adsorptioninhibitor onto a metal surface in acidic medium.isotherm is more general than the Langmuir isotherm,does not assume a homogeneous surface or constanttential. The DR equation is [43]:

ax K 2

is the maximum surface coverage, K is the constantdsorption energy (mol2 kJ2), is Polanyi potential. Theential (kJmol1) is written as:

1 + 1Cinh

)

988 N. Caliskan, E. Akbas / Materials Chemistry and Physics 126 (2011) 983988

adsorption isotherm model gave adsorption energies of 3.25 and3.22kJmol1, respectively, for DHPM I and DHPM II at 298K. Theadsorption energy values provide information about the adsorp-tion mechanism, i.e. whether it involves chemical or physicaladsorption. Thus, if the value of adsorption energy is between8kJmol1 and 16kJmol1, the adsorption process corresponds toion exchange. Conversely, if the adsorption energy is less than8kJmol1, the adsorption process is physical in nature [42,43].

The mean free energy of the adsorption E is

E = (2K )0.5

In the present work were less than those expected for chemicaladsorption process, thereby suggesting that the adsorption mecha-nismmaybe a combinationof electrostatic interaction andphysicalsorption.

4. Conclusions

The inhibehavior ofdifferent te

1. Thepyrimless steel

2. The inhib3. The addi

anodic aDHPM Iwith incrto be of athe largemay be cmixed-tythe inhib

4. The neginhibitor

5. The adsoimatedmodels. Dadsorbedanism.

Acknowled

This studUniversity,

References

[1] A. Galal, N[2] A.S. Foud

(2010) 53

[3] S.A. Abd El-Maksoud, A.S. Fouda, Mater. Chem. Phys. 93 (2005) 84.[4] J. Aljourani, M.A. Golozar, K. Raeissi, Mater. Chem. Phys. 121 (2010) 320.[5] R. Hasanov, S. Bilge, S. Bilgic, G. Gece, Z. Klc, Corros. Sci. 52 (2010) 984.[6] S.A. Abd El-Maksoud, Appl. Surf. Sci. 206 (2003) 129.[7] F. Xu, J. Duan, S. Zhang, B. Hou, Mater. Lett. 62 (2008) 4072.[8] Y. Abboud, A. Abourriche, T. Saffaj, M. Berrada, M. Charrouf, A. Bennamara, N.

Al Himidi, H. Hannache, Mater. Chem. Phys. 105 (2007) 1.[9] H.S. Awad, S.A. Gawad, Anti-Corros. Method Mater. 52 (2005) 328.

[10] A. Chetouani, A. Aouniti, B.Hammouti,N. Benchat, T. Benhadda, S. Kertit, Corros.Sci. 45 (2003) 1675.

[11] G. Bereket, C. gretir, M. Yaman, E. Hr, J. Mol. Struct. (Theochem) 625 (2003)31.

[12] S.A. Ali, H.A. Al-Muallem, M.T. Saeed, S.U. Rahman, Corros. Sci. 50 (2008)664.

[13] S. Bilgic, N. Calskan, J. Appl. Electrochem. 31 (2001) 79.[14] R. Hasanov, M. Sadkoglu, S. Bilgic, Appl. Surf. Sci. 253 (2007) 3913.[15] M.A. Elmorsi, A.M. Hassanein, Corros. Sci. 41 (1999) 2337.[16] N.A. Hassan, Molecules 5 (2000) 827.[17] M. Pemmsin, C. Lnu-Due, F. Hoguet, C. Gaultier, J. Narcisse, Eur. J. Chem. 23

(1988) 543.[18] P.A.S. Smith, R.O. Kan, J. Org. Chem. 29 (1964) 2261.[19] A. Cannito, M. Pemmsin, C. Lnu-Due, F. Hoguet, C. Gaultier, J. Narcisse, Eur. J.

Chem. 25 (1990) 635.[20] S. Nega, J. Aionso, A. Diazj, F. Junquere, J. Heterocycl. Chem. 27 (1990)

.etsuo132, 8etsuo. Chak. Appl.. Chaktr. 11Shish. KappL.Y. IvaR (Izvikh NaF. Aslaslano(200

. Emre. Shanppl. E. Rame. Musarud

Li, Q.. Shuk. Pavi1.. Hermolmaz1.olmaz. Rame. Abd EAshas6.OzcanBehpo3.ilgic,. Abd EObot,. Kul,. Sol7.bition and adsorption effect of DHPMs on the corrosionthe stainless steel in 0.5M H2SO4 was studied using

chniques. The following points can be emphasized:

idine compounds studied are good inhibitors for stain-in 0.5M H2SO4.ition efciency increases with inhibitor concentration.tion of DHPM I and DHPM II induces a decrease in bothnd cathodic currents. The corrosion potential (Ecorr) ofwas observed to shift towards more noble potentialseasing additive concentration, indicating the inhibitorsnodic character and formation of a surface lm. Sincest displacement exhibited by DHPM II was 53mV, itoncluded that this inhibitor should be considered as ape inhibitor. The presence of the sulfur atom increasesition efciency.ative values of Gads show that the adsorption ofmolecules on the metal surface is spontaneous.rption DHPMs on stainless steel surface can be approx-by Langmuir and DubininRadushkevich isothermubininRadushkevich model suggests that DHPMs areon stainless steel surface by physical adsorptionmech-

gement

y was supported by the Research Fund of Yznc YlVan, Turkey.

.F. Atta, M.H.S. Al-Hassan, Mater. Chem. Phys. 89 (2005) 38.a, M. Abdallah, S.M. Al-Ashrey, A.A. Abdel-Fattah, Desalination 2508.

269[21] S. T

62,S. T

[22] P.KIntP.KAbs

[23] C.J.[24] C.O[25] (a)

USSesk(b)

[26] F. A182

[27] K.C[28] A.V

J. A[29] S.V[30] A.Y

Kam[31] W.[32] S.K[33] M.K

381[34] A.A[35] R. S

594[36] R. S[37] S.V[38] S.A[39] H.

344[40] M.[41] M.

107[42] S. B[43] S.A[44] I.B.[45] A.R[46] M.M

131, T. Mikio, H. Hidetoshi, H. Daijiro, I. Akira, Jpn. Kokai Tokyo Koho JP84 (1987);, T. Mikio, Chem. Abstr. 107 (1987) 198350h.aravorty, W.J. Grelnlee, K. Dooseap, N.B. Mantlo, A.A. Patchett, A.P.C.T.WO 92.20.687.156 (1992);aravorty, W.J. Grelnlee, K. Dooseap, N.B. Mantlo, A.A. Patchett, Chem.8 (1993) 213104d.oo, K.S. Jain, J. Heterocycl. Chem. 29 (1992) 883.e, Molecules 3 (1998) 1.novskaya, Z.D.Dubovenko,V.P.Mamaev, Inst.Org.Khim.Novosibirsk,estiya Sibirskogo Otdeleniya Akademii Nauk SSSR, Seriya Khimich-uk) 6 (1969) 132;noglu, Master Thesis, Yuzuncu Yil University, FBE Van, Turkey, 2007.

glu, E. Akbas,M. Snmez, B. Anl, Phosphorus Sulfur SiliconRelat. Elem.7) 1589.gul, E. Duzgun, O. Atakol, Corros. Sci. 48 (2006) 3243.bhag, T.V. Venkatesha, R.A. Prabhu, R.G. Kalkhambkar, G.M. Kulkarni,lectrochem. 38 (2008) 279.sh, A.V. Adhikari, Corros. Sci. 50 (2008) 55.a, A.A.H. Kadhum, A.B. Mohamad, M.S. Takriff, A.R. Daud, S.K.in, Corros. Sci. 52 (2010) 526.He, S. Zhang, C. Pei, B. Hou, J. Appl. Electrochem. 38 (2008) 289.la, M.A. Quraishi, Mater. Chem. Phys. 120 (2010) 142.thra, T.V. Venkatesha, K. Vathsala, K.O. Nayana, Corros. Sci. 52 (2010)

as, M.S. Morad, Corros. Sci. 50 (2008) 2710., G. Kardas, M. Culha, B. Yazc, M. Erbil, Electrochim. Acta 53 (2008)

, Corros. Sci. 52 (2010) 3321.sh, A.V. Adhikari, Mater. Chem. Phys. 115 (2009) 618.l-Maksoud, Int. J. Electrochem. Sci. 3 (2008) 528.

si-Sorkhabi, B. Shaabani, D. Seifzadeha, Electrochim. Acta 50 (2005)

, I. Dehri, M. Erbil, Appl. Surf. Sci. 236 (2004) 155.ur, S.M.Ghoreishi,N. Soltani,M. Salavati-Niasari, Corros. Sci. 51 (2009)

N. Caliskan, Appl. Surf. Sci. 152 (1999) 107.l-Maksoud, Mater. Corros. 54 (2003) 106.N.O. Obi-Egbedi, N.W. Odozi, Corros. Sci. 52 (2010) 923.N. Caliskan, Adsorpt. Sci. Technol. 27 (2009) 85.omon, S.A. Umoren, I.I. Udosoro, A.P. Udoh, Corros. Sci. 52 (2010)

The inhibition effect of some pyrimidine derivatives on austenitic stainless steel in acidic mediaIntroductionExperimentalPreparation of electrodeMaterialsTest solutionsElectrochemical measurements

Results and discussionPolarization measurementsLinear polarization measurementsElectrochemical impedance spectroscopy measurements (EIS)Adsorption isotherm

ConclusionsAcknowledgementReferences