Inhibitive Effect of Some Natural Naphthenates as Corrosion Inhibitors on the Corrosive...

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I nternational Jour nal of Scientif ic Research in Environmental Sciences (I JSRES), 1(8), pp. 166-178, 2013Available online at http://www.ijsrpub.com/ijsres

ISSN: 2322-4983; 2013 IJSRPUB

http://dx.doi.org/10.12983/ijsres-2013-p166-178

166

Full Length Research Paper

Inhibitive Effect of Some Natural Naphthenates as Corrosion Inhibitors on theCorrosive Performance of Carbon Steel in CO2-Saturated Brine

Vagif M. Abbasov1, Hany M. Abd El-Lateef1, 2*, Sevinc A. Mamedxanova1, Leylufer. I. Aliyeva1, Teyyub A.

Ismayilov1, Musayev J. Ilham

1, Orkhan A. Aydamirov

1, Fariz A. Amirov

1

1Mamedaliev Institute of Petrochemical Processes, National Academy of Sciences of Azerbaijan, AZ1025 Baku, Azerbaijan

2Chemistry Department, Faculty of Science, Sohag University, 82524 Sohag, Egypt

*Corresponding Author: [email protected]

Received 26 April 2013; Accepted 07 June 2013

Abstract. Two surfactants [sodium and potassium salts of naphthenic acids] were synthesized by liquid-phase oxidation

process of the naphtha fraction of the Baku crude oil and their chemical structure was confirmed by FT-IR spectroscopy. Thesurface tension at 298K was measured; the critical micelle concentration (CMC) and some surface active parameters werecalculated. The inhibition efficiency (%) of these surfactants has been studied by both Linear polarization resistance corrosion

rate and Potentiodynamic polarization measurements at 50 C. The data showed that, the presence of investigated inhibitors

results a high decrease in the corrosion rate. The inhibition efficiency increases with an increase in the inhibitor dose, getting

maximum inhibition efficiency 99.48% at 100 ppm of potassium salt. The Tafel polarization results indicate that the inhibitors

act as mixed inhibitors. Tafel slopes are approximately constant and independent on the inhibitor concentration. The adsorption

of the inhibitors on the carbon steel surface obeys Langmuirs adsorption isotherm. The thermodynamic parameters ofadsorption revealed a strong interaction between the inhibitors and the corroding carbon steel surface.Key words: Petroleum acids, Carbon Steel, surfactants, corrosion inhibition, Carbon Dioxide Corrosion.

1. INTRODUCTION

Corrosion of carbon steel is a significant problem inthe oil and gas production and transportation systemsand causes significant economic loss (Okafor et al.,2009). CO2 corrosion of carbon steels has been one ofthe most common corrosion problems in oil and gas

industry. Carbon dioxide dissolves in the presence ofa water phase, forming carbonic acid, which iscorrosive to carbon steel (Lopez et al., 2003a). Theunderstanding of CO2 corrosion mechanisms underthe effects of many mechanical and environmental

factors, such as flow, temperature, pressure, oilwaterratio, pH, solution chemistry, and corrosion productlayer, has been of great concern in corrosion field(Yin et al., 2009).

The use of inhibitors is one of the most practicalmethods for protection against corrosion. Theinhibitors, which reduce corrosion on metallicmaterials, are inorganic inhibitors, organic inhibitors,surfactant inhibitors and mixed material inhibitors.Surfactants are special type of organic compounds andexhibit unique properties due to their amphiphilicmolecule. This is the reason of their wide application

in the field of inhibition of metals against corrosion. Amolecular layer of surfactants is formed as a result ofthis attraction with the construction of a hydrophobicbarrier, which prevent the contact of the metal surfacewith the environment. The surfactant inhibitors have

many advantages such as high inhibition efficiency,low price, low toxicity and easy production (Abbasovet al., 2013a; Abbasov et al., 2013b; Abd El-Lateef etal., 2012a; Stoyanova et al., 1997; Abdallah et al.,2009; Joseph and Rajendran, 2001).The adsorption ofthe surfactant on the metal surface can markedlychange the corrosion-resisting property of the metal

(Abd El-Lateef et al., 2012b), and so the study of therelationship between the adsorption and corrosioninhibition is of great importance.

Salts of naphthenic acids, which are naphthenates,are widely used as hydrophobic sources of metal ions

in diverse applications. Metal naphthenatesare coordination complexes. They have the formulaM(naphthenate)2 or are basic oxides with the formulaM3O(naphthenate)6. The naphthenates are highlysoluble in organic media, such as paints. They haveindustrial applications includingsynthetic detergents, lubricants and corrosioninhibitors (Nora et al., 2005).

In this study, two surfactants (sodium andpotassium salts of naphthenic acids) were synthesizedby liquid-phase oxidation process ofthe naphtha fraction of the Baku crude oil. The surface

activities of these surfactants were determined. Theapplicability of these surfactants as corrosioninhibitors for carbon steel were estimated by Linearpolarization resistance corrosion rate and
mailto:[email protected]://en.wikipedia.org/wiki/Naphthahttp://en.wikipedia.org/wiki/Crude_oilhttp://en.wikipedia.org/wiki/Coordination_complexhttp://en.wikipedia.org/wiki/Detergenthttp://en.wikipedia.org/wiki/Lubricanthttp://en.wikipedia.org/wiki/Naphthahttp://en.wikipedia.org/wiki/Crude_oilhttp://en.wikipedia.org/wiki/Crude_oilhttp://en.wikipedia.org/wiki/Naphthahttp://en.wikipedia.org/wiki/Lubricanthttp://en.wikipedia.org/wiki/Detergenthttp://en.wikipedia.org/wiki/Coordination_complexhttp://en.wikipedia.org/wiki/Crude_oilhttp://en.wikipedia.org/wiki/Naphthamailto:[email protected]


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Inhibitive Effect of Some Natural Naphthenates as Corrosion Inhibitors on the Corrosive Performance of Carbon Steel

in CO2-Saturated Brine

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Potentiodynamic polarization measurements in CO2-saturated 1% NaCl solution at 50 C.

2. MATERIALS AND METHODS

2.1. Chemical composition of carbon steel alloy

The rotating disk working electrodes for tests weremade of carbon steel grade 080A15 and have an areaof 4.55 cm2 with a chemical composition (wt%) C

0.18%, Si 0.17%, Mn 0.70%, P 0.011%, S 0.03%, Ni0.0%, Cr 0.01% and Fe balance. The data was

provided by European Corrosion Supplies Ltd

2.2. Synthesis of Surfactant inhibitors

The surfactants used as inhibitors were synthesized inour laboratory based on petroleum acids. The newseries of the complex surfactants were synthesizedfrom naphthenic acids isolated from light oil fractions(Tb= 180-350 C) (Abbasov et al, 2012c). Two typesfrom inhibitors were synthesized in high purity by thefollowing compositions: [R-COONa (I) and R-COOK(II)]. The chemical structure of the synthesized

surfactants was characterized by using FT-IR,Spectrum BX spectrometer using KBr disks.

2.3. Preparation of solutions

The aggressive solution, 1% NaCl, was prepared bydissolving of analytical grade NaCl in distilled water.The concentration range of the prepared surfactantswas from 25 to 100 ppm used for corrosionmeasurements. All inhibitors solutions were preparedusing distilled water.

2.4. Corrosion measurements

The measurements were performed on the rotatingcylinder electrode. This electrode was used for one

time. The reference electrode was Ag/AgCl Electrodeto which all potentials are referred.

Before beginning the experiment, the prepared 1%- of sodium chloride solution was stirred by a

magnetic stirrer for 60 min in 1000 ml cell. Then thiscell was thermostated at 50 C for 1 hour under a CO2pressure of 0.9 bars. The solution was saturated withcarbon dioxide. To remove any surface contaminationand air formed oxide, the working electrode was kept

at1500 mV (Ag/AgCl) for 5 min in the testedsolution, disconnected shaken free of adsorbedhydrogen bubbles and then cathodic and anodicpolarization was recorded. ACM Gill AC instrumentconnected with a personal computer was used for the

measurements.

2.4.1. Potentiodynamic polarization measurements

The extrapolation of cathodic and anodic Tafel lineswas carried out in a potential range 100 mV withrespect to corrosion potential (E

corr) at scan rate of 1

mV/s.

2.4.2. Linear polarization resistance corrosion rate

The LPR method is ideal for plant monitoring offering

an almost instantaneous indication of corrosion rate,allowing for quick evaluation of remedial action and

minimizing unscheduled downtime. The prepared 1%- of the solution sodium chloride was stirred by amagnetic stirrer for 60 min in 4000 ml. The preparedsolution poured into the 4 glass beakers (1000 ml for

each one). Then these beakers were placed on a heaterat 50 C for 1 hour under a pressure of 0.9 bars. Thesolution was saturated with carbon dioxide. Afterthat, the electrodes were placed in the medium and areconnected through a potentiometer ACM GILL AC.The surface of working electrode is cleaned byacetone before using, these electrodes are using forone time. After 1 hour, except for 1 beaker, the

remaining 3 is fed with the suitable amount ofinhibitor and continued supply of CO2 under pressureof 0.9 bar until the end of the experiment.

The potential of the working electrode was varied

by a CoreRunning programme (Version 5.1.3.)through an ACM instrument Gill AC. TheCoreRunning programme converts a corrosion currentin mA/cm

2to a corrosion rate in mm/year. A

cylindrical carbon steel rod of the composition080A15 GRADE STEEL was used as a workingelectrode. Gill AC technology allows measure DC andAC signals using standard Sequencer software. Asmall sweep from typically 10 mV to +10 mV at 10mV/min around the rest potential is performed.

2.5. Surface tension measurements

The surface tensions were determined by DuNouy

Tensiometer, Kruss Type 8451 and the temperaturewas maintained precisely at 25 C. Critical micelle

concentration (CMC) values of surfactants weredetermined, according to the break points in plots ofthe surface tension versus ln molar concentration ofinvestigated surfactants.

3. RESULTS AND DISCUSSION

3.1. Chemical structure of the synthesized

surfactants

The FT-IR spectrum of the naphthenic acid, shows abroad OH stretch found at 3200-2700 cm-1; the strong


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signal at 1712 cm-1

was due to a carbonyl group(C=O). The strong signal at 1289 cm

-1was due to a C-

O stretch; the signal at 1369 cm-1 was due to a C-O-H.The FT-IR absorption spectra of inhibitor IIconfirmed that, the disappearance of OH band of acid

(broad band), this confirmed that, the replacement ofH atom in carboxylic group by K atom to form COOK. FTIR spectra confirmed the expectedfunctional groups in the synthesized anionicsurfactant.

3.2. LPR corrosion rate

The linearpolarization-resistance (LPR) corrosionrate bubble-test method involves evaluating thecorrosion of a given metal in simulated brine saturated

with CO2 at a temperature equivalent to that in thefield. During the test, CO2 gas is sparged continuouslyinto the test solution. The rate of corrosion isdetermined instantaneously with the LPR corrosionrate technique, in which a small direct-current voltageis applied to a pair of identical electrodes and theresultant current is measured.

Figure 1 shows that, the change in corrosion rate

(CR) with time for carbon steel in CO2-saturated 1%NaCl solution containing different concentrations

form inhibitorII (K-salt) at 50 C. The inhibitor wasadded after 1 hour of exposure because at this time thecorrosion potential got stable, allowing themeasurement of the CR prior the injection of theinhibitor. The initial corrosion rate, without inhibitor,

was measured to be between 3.45 and 5.03 mm y-1. Itcan be observed from Figure 1 that, the CR, in theabsence of inhibitor, tends to increase with time. Theincrease in CR has been attributed to the galvaniceffect between the ferrite phase and cementite (Fe3C)

which is a part of the original steel in the non-oxidizedstate and accumulates on the surface after the

preferential dissolution of ferrite (-Fe) into Fe2+

(Staicopolus, 1963). Fe3C is known to be lessactive than the ferrite phase. Therefore, there is apreferential dissolution of ferrite over cementite,

working the former as the anode and latter as thecathode, favoring the hydrogen evolved reaction(HER) during the corrosion process (Crolet et al.,1998; Videm et al., 1996).

Variation of the corrosion rate for inhibitor II atdifferent concentrations is presented in Figure 1.Corrosion parameters were calculated on the basis ofLPR corrosion rate test. The inhibition efficiency (

%) and surface coverage () were calculatedaccording to the following equations:

where CRo is the corrosion rate without inhibitorand CRi is the corrosion rate when inhibitor is present.It can be seen that the presence of inhibitors results ahigh decrease in the rate of corrosion. In the case ofthese inhibitors, the corrosion rate decreases as theinhibitor concentration increases, getting maximuminhibition efficiency ranged between 98.49 and99.48% at 100 ppm after 20 hour of exposure (Table1). This trend may results from the fact thatadsorption and surface coverage increase with the

increase in concentration; thus the surface iseffectively separated from the medium (El-Sayed etal., 2010).

Table 1 shows the calculated values of corrosionrates, the inhibition efficiencies and the surface

coverage in the absence and presence of differentconcentrations of different inhibitors at 50 C. Ageneral trend is observed in presence of the studied

inhibitors, a decrease in the corrosion rate of carbonsteel in presence of these surfactants compared to theblank (inhibitor free solution). By increasing theconcentration of the surfactants, a further decrease in

corrosion rate of carbon steel was observed. The

maximum inhibition efficiency (%) was obtained at100 ppm of inhibitors.. This indicates that theinhibitory action of the inhibitors against carbon steelcorrosion can be attributed to the adsorption of thesemolecules on the metal surface, limits the dissolutionof carbon steel, and the adsorption amounts ofsurfactants on carbon steel increase withconcentrations in the corrosive solutions (Taleb andMohamed, 2011).

Figure 2 shows the variation of the corrosion rate

with time for carbon steel in CO2-saturated brinecontaining 100 ppm from different surfactants at 50C. This plot indicates that, the presence of differentinhibitors decreases the rate of corrosion. The dataindicate that, the inhibition efficiency of carbon steel

in CO2-saturated brine in the presence of inhibitor II(K-salt) more than that obtained of inhibitor I (Na-salt).

The high inhibition efficiency obtained in CO2-saturated solution in the presence of studied inhibitorscan be attributed to the formation of a protective filmof iron carbonate (FeCO3) as follows (Lopez et al.,

2003b):


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The anodic dissolution for iron in carbonic acidsolutions gives ferrous ions (Ogundele and White,1986).

Fe Fe2+

+ 2e-

(7)According to these processes, a corrosion layer

was formed on the steel surface. The properties of theformed layers and its effect on the corrosion rate areimportant factors to take into account when studying

the corrosion of steels in CO2 environments. Ogundeleand White suggested that, iron carbonate, FeCO3, maybe important in the formation of protective layers onsteel surface (Ogundele and White, 1986). Theformation of iron carbonate can be explained by usingthe following Eq. (Migahed et al, 2006).

Fe2+ +2

3CO FeCO3 (8)

3.3. The extrapolation of cathodic and anodic Tafel

lines

The inhibiting effect of the synthesized compounds onthe corrosion reaction of carbon steel in CO2-saturatedNaCl solution was investigated using theelectrochemical polarization method. The polarization

technique was adopted to determine both cathodic and

anodic polarization curves. It is also used to calculatethe corrosion currents from the extrapolation of Tafellines to pre-determined open circuit potential. This is

achieved by measuring the potentialcurrentcharacteristics of the metal/solution system under

consideration with the aid of a potentiostat.Figure 3 shows the influence of inhibitor I

concentrations on the Tafel cathodic and anodic

polarization characteristics of carbon steel in CO2-saturated solution at scan rate 1 mV/s and at 50 C.Corrosion parameters were calculated on the basis ofcathodic and anodic potential versus current densitycharacteristics in the Tafel potential region (Tremontet al, 2000; Schultze and Wippermann, 1987). Steadystate of open circuit corrosion potential (Ecorr) for theinvestigated electrode in the absence and presence ofthe studied inhibitor was attained after 4560 minfrom the moment of immersion. Corrosion currentdensity (Icorr) of the investigated electrodes wasdetermined (El-Sayed, et al, 2011), by extrapolation of

cathodic and anodic Tafel lines to corrosion potential(Ecorr). The inhibition efficiency expressed as percentinhibition (%) is defined as:

Where Iuninh. and Iinh. are the uninhibited andinhibited corrosion currents. The inhibited corrosion

currents are those determined in the presence of thestudied surfactants used in this investigation. Theuninhibited corrosion currents were determined inpure (inhibitor free) CO2-saturated 1% NaCl solutionat the same temperature. It can be seen that thepresence of surfactants molecule results a markedshift in both cathodic and anodic branches of thepolarization curves towards lower current densities.This means that, the inhibitors affect both cathodicand anodic reactions. It was found that, both anodicand cathodic reactions of carbon steel electrodecorrosion were inhibited with increasing concentration

of synthesized inhibitors. These results suggest thatnot only the addition of synthesized inhibitors reduce

anodic dissolution but also retard the hydrogenevolution reaction.

The electrochemical parameters Ecorr, Icorr,inhibition efficiency (%), anodic and cathodic Tafelslopes (a , c) obtained from the polarizationmeasurements were listed in Table 2. The dataexhibited that, the corrosion current density (Icorr)decreases, and the inhibition efficiency (%) increasesas the concentration of inhibitors is increased. Theseresults suggest that retardation of the electrodesprocesses occurs, at both cathodic and anodic sites, asa result of coverage of these sites by surfactantsmolecules. The results also indicate that, thepercentage inhibition efficiency ( %) of the inhibitor

(II) is greater than that of the inhibitor (I), thereby;firmly agree with aforementioned results of LPRcorrosion rate.


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Fig. 1: Variation of the Corrosion rate with time for carbon steel in CO2-saturated 1 % NaCl solution containing different

concentrations of inhibitorII (K-salt) at 50 C.

Fig. 2: Variation of the Corrosion rate with time for carbon steel in CO2-saturated 1% NaCl solution containing 100 ppm of

different inhibitors at 50 C.

The corrosion potential Ecorr values of allsynthesized inhibitors were shifted slightly towardboth cathodic and anodic directions and did not show

any definite trend in CO2-saturated brine. This may beconsidered due to the mixed-type behaviour of thestudied inhibitors. It can be observed, the shift in Ecorrthat is characteristic of anodic and anodic/cathodicinhibitor (Lpez et al, 2005). It was explained that this

shift in Ecorr is due to active sites blocking effect thatoccurs when an inhibitor is added (Cao, 1996). In the

case of CO2 corrosion the anodic and cathodicreactions are the oxidation of iron and the reduction ofhydrogen, respectively (Nordsveen et al., 2005). If it

is considered that the active sites on the metal surfaceare the same for both reactions before adding theinhibitor, it is logical the change in Ecorr when the

inhibitor is present because its adsorption changethose active sites and therefore the anodic andcathodic reaction rates (Farelas and Ramirez, 2010).

The fact that the slopes of the cathodic (a) andanodic (c) Tafel lines in Table 2 remain almost

unchanged upon addition of the inhibitors. Theseresults indicate that this inhibitor acts by simply

blocking the available surface area. In other words,the inhibitor decreases the surface area for corrosionof the investigated metal, and only causes inactivation


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of a part of the surface with respect to corrosivemedium. On the other hand, the cathodic Tafel slopes(c) are also found to be greater than the respectiveanodic Tafel slopes (a). These observations arecorrelated with the fact that the cathodic exchange-

current density values are less than those of the anodiccounter parts. It can be concluded that the overall

kinetics of corrosion of carbon steel alloy in CO2saturated solution are under cathodic control.

For all studied inhibitors, the common ground wasthat the corrosion current density decreased and theinhibition efficiency increased with increasing

inhibitors concentration. The highest inhibitionefficiency was 98.49 % for inhibitorII (K-salt) at100ppm.

Table 1: The corrosion parameters obtained from LPR corrosion rate measurements for carbon steel electrode in CO2-

saturated brine in the absence and presence of various concentrations of investigated surfactants at 50 C.

Fig. 3: Tafel polarization curves for carbon steel in CO2-saturated 1% NaCl solution containing different concentration of

inhibitor (I) at 50 C.


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Table 2: Corrosion parameters obtained from Tafel polarization for carbon steel in CO2-saturted 1% NaCl solution

in the absence and presence of different concentrations of the prepared surfactants at 50 C.

3.4. Surface tension and surface active properties

The values of surface tension () were measured at303 K for various concentrations of the synthesizedsurfactants. The measured values of () were plottedagainst ln of the surfactant concentration, ln C (Fig.

4). The intercept of the two straight lines designatesthe CMC, where saturation in the surface adsorbedlayer takes place. The plot showed that the surfactantwas molecularly dispersed at low concentrationleading to a reduction in surface tension. This

reduction increases with increasing concentration. At

high concentration, however, when a certainconcentration was reached (CMC), the surfactantmolecules form micelles, which were in equilibriumwith the free surfactant molecules (Migahed et al.,2006).

The surface active properties of the surfactant,effectiveness (cmc), maximum surface excess (max),and minimum area per molecule (Amin) werecalculated using the following equations (Rosen,1978):

Where /lnCis maximum slope, 0 is the surfacetension of pure water, cmc the surface tension atcritical micelle concentration, NA is the Avogadrosnumber (6.023 10

23molecules/mol),R is the molar

gas constant (R= 8.314 J/(mol K)) and T is the

absolute temperature = (tC+273),o

micG is the Gibbs

free energy of micellization,0

adsG is the Gibbs free

energy of adsorption(Badawi et al., 2007).

The data presented in Table 3 show some of thesurface active properties for the investigatedsurfactants. The results indicate that, the consequentincrease in ofmax leads to crowding at the interface,which causes a decrease in Amin values. The values of

effectiveness (cmc) at 298 K indicate that the preparedcompounds gives large reduction of surface tension atCMC, so that, these compounds acts as effectivecorrosion inhibitors for carbon steel in CO2- saturated1% NaCl solutions.

The free energy changes of micellization andadsorption showed negative sign showing thespontaneity of the two processes at 25 C (Table 3).

Moreover,0

adsG increase in negativity than

o

micG .

That showed the higher tendency of these surfactantstowards adsorption rather than micellization. Then theadsorption will be accompanied with micellization atlast. The tendency towards adsorption was referred to


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the interaction between the aqueous phases and thehydrophobic chains which pump the surfactant

molecules to the interface (Alsabagh et al., 2006).

Table 3: The critical micelle concentration and surface parameters of the synthesized surfactants

3.5. Adsorption isotherm and thermodynamic

parameters

Basic information on the interaction between theinhibitor molecules and metal surfaces could be

provided from the adsorption isotherms. The values of

surface coverage () which were defined as in thefollowing equation:

A correlation between and inhibitorconcentration in the corrosive medium can be

represented by the Langmuir adsorption isotherm (Taoet al., 2009).

Where Kads is the equilibrium constant of theinhibitor adsorption process and Cinh. is the inhibitor

concentration.Plots of Cinh/versus Cinh yielded a straight line as

shown in Fig. 5, which suggested that at 323 K theadsorption of investigated inhibitors on metal surfaceobeyed Langmuir adsorption isotherm model. Thisisotherm assumed that the adsorbed moleculesoccupied only one site and there was no interaction

with other molecules adsorbed. The linear regressioncoefficients (r) and the slopes parameter were shownin Table 4. All correlation coefficient (r > 0.997)

indicated that the inhibition of carbon steel by studiedsurfactants was attributed to the adsorption of

inhibitors on the metal surface. However, the slopes ofthe Cinh/ versus Cinh plots were close to 1 and

showed a little deviation from unity which meant non-ideal simulating (Badawy et al., 2006) and unexpectedfrom Langmuir adsorption isotherm. They might bethe results of the interactions between the adsorbedspecies on the metal surface (Migahed et al., 2003;Azim et al., 1974).

Kads values could be calculated from the intercepts

of the straight lines on the Cinh/ -axis, the Kads wasrelated to the standard free energy of adsorption,

o

adsG ; with the following equation (Flis and

Zakroczymski, 1996):

The value 55.5 in the above equation was the molarconcentration of water in solution in mol/L (Azim etal., 1974). The relatively high value of the adsorptionequilibrium constant (Kads; Table 4) reflects the high

adsorption ability of these surfactants on the metalsurface (Abd El-Lateef et al., 2012c).It is also noted

that, the high value ofKads for inhibitor II indicatestronger adsorption on the carbon steel surface than

the inhibitor I. Large values of Kads imply moreefficient adsorption hence better inhibition efficiency(Refay et al., 2004).The high and negative values of free energy of

adsorption ( oadsG ) indicate spontaneous adsorption

and strong interaction of the inhibitor molecule with

the carbon steel surface. Generally, values ofo

adsG


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up to -20 kJ mol-1

are consistent with physisorption,while those around -40 kJ mol

-1or higher are

associated with chemisorption as a result of thesharing or transfer of electrons from organicmolecules to the metal surface to form a coordinate

bond (Farhat and Quraishi, 2011). In the present

study, theo

adsG values obtained for the surfactants I

and II on carbon steel in CO2-saturated 1 % NaClsolution are -44.71 and -45.92 kJ mol

-1, respectively.

This indicates that the adsorption of studied inhibitors

is typical chemisorption.

Fig. 4: Change of surface tension () with the concentration of the surfactants at 25 C.

Fig. 5: Langmuir plots for inhibitors I and II in CO2-saturated brine obtained from the extrapolation of cathodic and anodic

Tafel lines at 50 C.

4. CONCLUSION

In this research, Linear polarization resistancecorrosion rate and Potentiodynamic polarizationmeasurements were used to study the corrosion

inhibition of carbon steel in CO2-saturated 1% NaClsolution using sodium and potassium salts of

naphthenic acids as corrosion inhibitors. The resultscan be summarized as follows.

a) The synthesized surfactant acts as an effectivecorrosion inhibitor for carbon steel in CO2-saturated1% NaCl solution.

b) The inhibition efficiency increased withincreasing concentration of the inhibitor.


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c) The inhibition efficiency (%) reached to 99.48% at 100 ppm of the inhibitorII.

d) Polarization measurements showed that theinhibitors act as mixed inhibitor.

e) The adsorption of the inhibitors on the metal

surface obeys Langmuir adsorption isotherm.

f) The higher value of the equilibrium adsorptionconstant (Kads. = 3.65 10

5) reflects the high

adsorption ability of the inhibitors molecules on thesurface of carbon steel.

Table 4: Thermodynamic parameters for the adsorption of inhibitors I and II in CO2-saturated brine on the

carbon steel surface at 323 K

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Prof. Dr. Vagif Maharram Abbasov, Doctor of chemical sciences (DSC), Azerbaijan National Academy

of Sciences, Institute of Petrochemical Processes, Director of Institute of Petrochemical Processes. He

is a Member of the Editorial Board of "Processes of Petrochemistry and oil refining journal" (Chief

Secretary). He is a Member of the American Chemical Society. He is an author on 250 papers in

international journals and more than 35 books. V. M. Abbasov has carried out the thorough researches

in the field of synthesis of antistatic additives to hydrocarbon liquids including to jet fuels. He for the

first time proposed the possibility for producing the displaced complexes of nitroalkanes and organic

acids with the transition metals, developed on their basis the high efficient and polyfunctional antistaticadditive. This additive was tested and commercialized in perm plant of aircraft engines. V. M. Abbasov

with coworkers has created in 1997 the polyfunctional waxy deposit corrosion inhibitor "Parkorin-1",

the commercial tests have been carried out in the Azerbaijan oil fields, jointly exploited by Turkish- Azerbaijan and by

TSNIIKP (Moscow city) has been recommended for application.

Dr. Hany M. Abd El-Lateef was born in Sohag, Egypt, in 1982. He received the master degree in

physical chemistry from the University of Sohag, Sohag, Egypt, in 2009, since that has worked in

different projects in the field of corrosion science. In 2010, he joined the department of chemical

resistance of materials and corrosion protection, institute of petrochemical processes, Azerbaijan

National Academy of Sciences, as a PhD student. He is one of the Editorial board of Chemistry Journal.

He is an author on 30 papers in international journals and two books. Hany is one of NACE

membership.

Dr. Sevinc A. Mamedxanov, Doctor of chemical sciences, Azerbaijan State Oil Academy. She is an

author on 50 papers in international journals. She obtained degree in Master of Science in

Petrochemistry from Azerbaijan State Oil Academy. She received his first degree in applied chemistry

from Azerbaijan State Oil Academy. Her research is focused on the Synthesis of various surfactants,

compounds soluble in oils and fuels, and their investigation as corrosion inhibitors, additives to fuels,

oils, polymeric stabilizers, development of theoretical bases for selecting corrosion inhibitors and

additives.

Prof. Dr. Leylufer Imran Aliyeva Doctor of Technical Sciences, Azerbaijan National Academy of

Sciences, Institute of Petrochemical Processes, Head of department. She is a Member of the EditorialBoard of "Processes of Petrochemistry and oil refining journal". She is an author on 180 papers in

international journals and more than 18 books. Her work focused on the synthesis of nitroalkanes

metallocomplexes, high-molecular amines and creation of polyfunctional antistatic additives, corrosion

inhibitors, inhibitor-bactericides and study of their action mechanism. She has created the high efficient

polyfunctional sulfurated hydrogen corrosion inhibitors based on -olifins with working capacity in themedia with H2S, CO2 content more than 25% vol.
http://www.google.com.eg/url?sa=t&rct=j&q=azerbaijan+neft+academy&source=web&cd=1&cad=rja&ved=0CDEQFjAA&url=http%3A%2F%2Fen.wikipedia.org%2Fwiki%2FAzerbaijan_State_Oil_Academy&ei=b1mFUb68HK6w4QTDl4CoDg&usg=AFQjCNGRjlbJ79143AtSz1mBwpRSBndHUA&bvm=bv.45960087,d.Ymshttp://www.google.com.eg/url?sa=t&rct=j&q=azerbaijan+neft+academy&source=web&cd=1&cad=rja&ved=0CDEQFjAA&url=http%3A%2F%2Fen.wikipedia.org%2Fwiki%2FAzerbaijan_State_Oil_Academy&ei=b1mFUb68HK6w4QTDl4CoDg&usg=AFQjCNGRjlbJ79143AtSz1mBwpRSBndHUA&bvm=bv.45960087,d.Yms


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Dr. Teyyub A. Ismayilov, Doctor of chemical sciences, Azerbaijan National Academy of Sciences,

Institute of Petrochemical Processes. He is an author on 50 papers in international journals. T. A.

Ismayilov has carried out the thorough and extensive researches in the field of creation of the corrosioninhibitors and obtained the following important results: on the basis of carbamide and amines there has

beer created a new method for synthesis of phosphate complexes and organized on their basis the

production and application of polyfunctional corrosion inhibitors.

Musayev Javidan Ilham is a Ph.D student in the sphere of quality control at the State EconomicUniversity of Azerbaijan. He received his first degree from The State Economic University in 2009

awarded with Bachelor of Science. He obtained Master degree of Science from The State Economic

University in 2012. His current research is focuses on synthesis and the review in quality of sulfonation

of acids and saline acids on plant origin.

Orkhan A. Aydamirov obtained his first degree from the Baku State University in chemistry in 2011.

He is junior researcher in Petrochemical Institute of Azerbaijan National Academy of Sciences. His

current research is focuses on corrosion inhibitors and conservation fluids. To date, he has published

several scientific articles related to corrosion inhibitors. He also interests in alternative energy sources

and biomass.

Dr. Fariz A. Amirov is an Assistant Professor in Azerbaijan State Oil Academy. He has more than 22

years research experience in the field of Petrochemistry. He has published over 70 refereed articles in

professional journals/proceedings. Dr. F. A. Amirov research has focused on alleviating problems

associated with oil industry issues from corrosion. He is editor and reviewer of some international

journals.

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