Microsoft Word - 73-88 73 | Chemistry 2016) عام 1العدد ( 29مجلة إبن الهيثم للعلوم الصرفة و التطبيقية المجلد Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 29 (1) 2016 Amino Acids as Environmentally-Friendly Corrosion Inhibitors for 2024 Aluminium Alloy in Akaline Medium Wisal A. Isa Zainab W. Ahmed Dept. of Chemistry/ College of Education for Pure Sciences (Ibn-Al-Haitham)/ University of Baghdad Received in:24/May/2015,Accepted in:23/June/2015 Abstract The corrosion behavior of 2024 aluminium alloy was investigated in alkaline medium (pH=13) containing 0.6 . in absence and presence of different concentrations of three amino acids separately [Methionine, Glutamice acid and Lysine] as environmentally friendly corrosion inhibitors over the temperature range (293-308)K. Electrochemical polarization method using potentiostatic technique was employed. The inhibition efficiency increased with an increase of the inhibitor concentration but decreased with increase in temperature . The maximum efficiency value was found with lysine =80.4 of 293 k and 10 . concentration of lysine. The adsorption of the amino acids was found to obey Langmuir adsorption isotherm . Some thermodynamic parameter ∆ and activation energy ∗ were calculated to demonstrate the mechanism of corrosion inhibition . The kinetic parameters were calculated using Arrhenius theory. Suitable mechanism was proposed for the corrosion of 2024 aluminium alloy in alkaline medium. The polarization measurements indicated that the inhibitor is of mixed type. The surface morphology of uninhibitied and inhibited samples were investigated using optical microscope. Key word: corrosion inhibition , 2024 alloy, Amino acids, Free energy of adsorption, Adsorption mechanism. 74 | Chemistry 2016) عام 1العدد ( 29لمجلد ا مجلة إبن الهيثم للعلوم الصرفة و التطبيقية Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 29 (1) 2016 Introduction Corrosion, which is an inevitable problem faced by almost all industries can be considered as one of the worst technical calamities of our time. Besides, from its direct costs in dollars, dollars, corrosion is a serious problem because it definitely contributes to the depletion of our natural resources. Corrosion studies have also become important due to increasing awareness of the need to conserve the worlds metal resources[1]. Now-a-day more attention has been paid to control the metallic corrosion , due to increasing use of metals in all fields of technology: Corrosion studies of aluminium and aluminium alloys have received considerable attention by researchers because of their wide industrial application and economic considerations[2]. Aluminium and aluminium alloys have emerged as alternate materials in aerospace and in some chemical processing industries. Due to their wide applications, they frequently come in contact with acids or bases during pickling, de-scaling, electrochemical etching and extensively used in chemical process industries. Most of the reported studies were conducted on corrosion of various metal and alloys in and media[3,4,5]. Sodium hydroxide usually used for degreasing purpose as a part of our studies with corrosion behavior of aluminium and aluminium alloys in sodium hydroxide medium and corrosion control of the same using green inhibitors[6]. As corrosion inhibitors, various substances both inorganic and organic can be used. While organic inhibitors reduce the corrosion through film formation, organic compounds act mostly via adsorption processes on the metal surface and complex formation. As most efficient organic corrosion inhibitors could be toxic and thus unacceptable for the environment, contemporary studies are directed towards the search for alternative inhibitors that would be ecologically acceptable, stable non toxic and available at a relatively low cost, these compounds referred to as “green”, ‘eco-friently”, or environmentally-friendly comprise both organic and inorganic inhibitors. Among the organic inhibitors are bio-mimickling green inhibitors, such as amino acids, were conducted. Amino acids are completely soluble in aqueous media and can be produced with purity at low costs, in addition amino acids contain hetero atoms such as N,O and S (in some of them) which can form protective films [7]. The present work aims to characterize the effect of three amino acids (methionine, glutamic acid and lysine) as corrosion inhibitors for 2024 aluminium alloy in alkali medium (pH=13) containing (3.5% w/w) sodium chloride at temperature range (293-308)K. The three A.A. tested are L-enantiomers , methionine contains sulphur. 2. Experimental 2.1 Materials Tested were performed on 2024 aluminium alloy specimen of the following composition given in Table (1). 2.2 Solution Solution was prepared from analytical grade chemicals and doubly distilled water. Sodium hydroxide was obtained from fluka while methionine, lysine and glutamic acid were obtained from Aldrich chemical Co.Ltd. All measurements were performed in alkaline solution (pH=13) containing 3.5% which have a comparable level to that of seawater. Double distilled water was used in all preparations. 75 | Chemistry 2016) عام 1العدد ( 29لمجلد ا مجلة إبن الهيثم للعلوم الصرفة و التطبيقية Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 29 (1) 2016 2.3 Potentiostatic polarization measurements The potentiostatic polarization measurements were performed in a conventional three- electrode glass cell with working volume 1000ml using Wenking M lab potentiostat. A working electrode was a sheet with circular shape (2 cm diameter and 2 mm thickness) which previously were grinded with emery papers of different graded (200,400,800,1200, and 2000) . Then they were polished mechanically with diamond paste using smooth cloth to surface mirror. The exposed surface area to the aggressive medium was 1cm2. A Pt counter electrode and silver – silver chloride as a reference electrode were used. Polarization measurements were performed at potentials from -200 mV to +200 mV at a scan rate of 2mV/s after steady state potential had been established in catholic or anodic direction . All measurements were carried out in alkaline solution (pH=13) of 3.5% in the absence and presence of three different concentrations of the inhibitors. The experimental result were reproducible and each experiment was carried out at least twice. 2.4 Optical microscopy measurements The electrode surface of 2024 aluminium alloy was analyzed by optical microscope type were analyzed by optical microscope type of (Nikon Eclipse ME 600, Japan) before and after immersion in the aggressive solution in the absence and presence of the optimum concentration of the amino acid at 25˚C. the specimens were washed gently with water,then dried carefully and examined without further treatments. OHH3C S O NH2 Methionine OHOH O NH2 O OH NH2 O NH2 Glutamic acid  lysine Chemical structures of the investigated amino acids Figure (8) showed the images of Aluminium Alloy 2024 surface which immersed in the aggressive solution with and without the addition of 10-2 mol. dm-3 of amine acids. It can be observed that the specimen surface was strongly damaged in absence of inhibitor due to metal dissolution in the aggressive solution. A number of pits distributed over the surface are seen Figure (8 b). However, no pits and cracks were observed in the micrograph after the addition of inhibitors to the aggressive solution Figure ( 8 c , 8 d )and (8 e). Inhibitor molecules adsorbed on active sites of Al an a smoother surface was observed when compared to the surface treated with uninhibited alkaline chloride solution. 76 | Chemistry 2016) عام 1العدد ( 29لمجلد ا مجلة إبن الهيثم للعلوم الصرفة و التطبيقية Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 29 (1) 2016 3. Results and discussion 3.1 Polarization curves Figure (1) showed the anodic and cathodic polarization curves of 2024 aluminium alloy in alkaline solution (pH=13) of 0.6 mol dm-3 (3.5% W.W ) at four temperatures in the range (293-308)K. Tafel extrapolation method was used to calculate the corrosion parameters , and from the polarization curves. The resetting data were displayed in Table (2) and these data show that corrosion current density increases with the increase of temperature, the corrosion potential nearly become more negative with the increase of temperature. Anodic and cathodic slopes shows variation in their values which can be attributed to the variation of the rate determining step (r.d.s) of the alloy dissolution reaction (Anodic) and the cathodic reaction involving hydrogen evolution produced by a partial cathodic reaction (reduction) of water. In view of the experimental observation, a tentative corrosion mechanism based on the electrochemical processes for dissolution of aluminium in may be suggested. This mechanism can be illustrated by anodic equations (1-4) and cathodic reaction equation(5) respectively for the anode process[8].   (1)   (2)    (3)  3   (4)  and, for the cathode process,   (5) The overall electrochemical process is: 2 2 3 (6) The dissolution of Al metal in the anodic reaction is accompanied by the catholic reaction which consumes the electrons release in the anodic process in order to form hydrogen atoms which react by combining with other adsorbed hydrogen atom to give bubbles of gas molecules at the metal surface   (7) 3.2 Corrosion activation parameters Arrehenius suggested the famous equation that correlates the temperature variation with rate of corrosion of 2024 Al alloy which is expressed by at a given concentration as[9] . ln ∗   (8) Here, A is frequency factor, ∗ is the activation energy, R is the gas constant and T is the absolute temperature. Equation(8) predicts that plotting of ln versus should be linear as we experimentally observed as in Figure(2). The slope of the line gives = ∗ , whereas the intercept of the line extrapolated to gives ln A. the value of activation energy equals to 17.5 and A= 19046398 10 molecule (Table 3). 77 | Chemistry 2016) عام 1العدد ( 29لمجلد ا مجلة إبن الهيثم للعلوم الصرفة و التطبيقية Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 29 (1) 2016 Entropy of activation ∆ ∗ was couldated from the value of A using the relationship[10]. ∗ exp ∆ ∗   (9) Where K is Boltzmann constant, h is Plank constant, and T is the temperature of the solution. The value of the entropy of activation was found to be 123.5 . the negative value of ∆ ∗ for 2024 Al alloy corrosion implies a loss in the overall degree of freedom throughout the formation of the activated complex (association rather than dissociation) for the reaction of 2024 Al alloy constituent with the negative species  leading to the formation of corrosion products, when the activated complex results[11]. 3.3. Corrosion inhibition of 2024 Al alloy by amino acids Figures (3,4) and (5) showed typical polarization curve of 2024 Al alloy in 0.6 3 solution (pH=13) containing three different concentrations of the amino acids (methionine, glutamic and lysine) separately as green inhibitors over the temperature range (293-308)K. Table (4-6) presents the polarization data and from these data it can be noticed that the addition of the amino acid caused a decrease in corrosion current densities of 2024 Al alloy and the inhibition effect of each amino acid increases as the concentration of the inhibitor increased in the range 10 10 at all temperatures of study. Table (5-6) shows the values inhibition efficiencies (IE%) which could be calculated from equation[13]. %   (10) Where, and are corrosion current densities in absence and presence of the inhibitor respectively. A maximum value of efficiency was fourd to be 80.4 293 10 conc. The activation parometers such as ∗ ∆ ∗ in the range of the studied temperatures (293- 308)K for corrosion inhibition of 2024 Al alloy in 0.6 solution in the presence of various concentrations of amino acids, methionine, glutamic acid and lysine separately were calculated from the well –known Arrhenius equation ∗ (11) The calculated values ∗ and ∆ ∗ are summarized in Table (7). In the presence of each amino acid separately, an increase in ∗ values was observed this increase in ∗ values in the presence of the inhibitor can be illustrated as follows[12]: higher values of ∗ were found in the presence of inhibitor than those without inhibitor, i.e. the addition of inhibitor raises the energy barrier for the corrosion process emphasizing the electrostatic character of the inhibitors adsorption on 2024 Al alloy surface. The entropy of activation ∆ ∗ values are negative in the presence of inhibitor implying the rate determining step for the activated complex is the association rather than the dissociation step. In the presence of the inhibitor ∆ ∗ moves in the direction of negative values Table (7) which implies the adsorption process is accompanied by a decrease in entropy which is the driving force for the adsorption of inhibitor onto 2042 Al alloy surface[13]. 3.4. Thermodynamic parameters of the adsorption isotherms Adsorption isotherms provide basic information on the nature of interaction between the inhibitor and 2024 Al alloy through applying some adsorption isotherm models. Two main types of interaction can describe the adsorption of inhibitors on the metal surface; they are 78 | Chemistry 2016) عام 1العدد ( 29لمجلد ا مجلة إبن الهيثم للعلوم الصرفة و التطبيقية Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 29 (1) 2016 physisorption and chemisorption, depending on the chemical structure of the inhibitor, the type of the corrosive medium, and the charge and nature of corrosive metal. In aqueous solutions , the metal surface is always covered with adsorbed water molecules. Therefore, the adsorption of the inhibitor molecules from an aqueous solution is a quasisubstihted process[8]., and the inhibitors that have the ability to be adsorbed strongly on the metal surface will hinder the dissolution reaction of the immersed metal into the corrosive medium. The mechanism of corrosion inhibition can be explained in terms of the adsorption behavior based on the calculated coverage degree[14]. The surface coverage Table (7) and the concentrations of inhibitor (amino acids) were tested by fitting to various isotherms like, Langmuir, Temkin and Freunflich. However, the best fit was obtained with Langmuir isotherm as shown in Figure (6) which is given by the following equation[12]. 1   (12) Where, is the equilibrium constant of the adsorption / desorption processes, and it reflects the affinity of the inhibitor molecules towards surface adsorption sites. From the intercepts of the straight lines on the axis Figure (6) leads to the equilibrium constant of the adsorption / desorption of amino acid process Table (8). The high value of reveals that the acid molecule possesses strong adsorption onto 2024 alloy surface. However, decreased with an increase of temperature indicating that adsorption of amino acid onto alloy surface was favorable at lower temperatures. The equilibrium constant of the adsorption/desorption was related to the standard free energy of adsorption according to equation[15]. ∆ ° ln 55.5   (13) Where, R is the universal gas constant , T is the absolute temperature, and value 55.5 is the concentration of water in solution. The standard free energy of adsorption was calculated and given in Table (8). Generally the values of ∆ ° ≅ 26 28 or less negative are associated with an electrostatic interaction between charged metal surface or more negative involves charge sharing or transfer from the inhibitor molecules to the metal surface to form a co-ordinate covalent bond . So it can be concluded that adsorption of amino acid onto 2024 Al alloy surface takes place thought both physical and chemical adsorption[16]. It is generally accepted that the first step in the adsorption of amino acid on the alloy surface usually involves the replacement of one or more water molecules adsorbed on the alloy surface. ⇌ . . .  (14) ≡ The inhibitor amino acid may then combine with freshly generated metal ions ( or other metal elements in the alloy). On the 2024 AR alloy surface forming metal inhibitor complex [17]. ⟶ 3   (15) ⟶   (16) Valuable information about the mechanism of corrosion inhibition can be provided by the values of thermodynamic parameters for the adsorption of the inhibitor. Thermodynamically, ∆ ° were related to the standard enthalpy ∆ ° and standard entropy ∆ ° according to [18]. 79 | Chemistry 2016) عام 1العدد ( 29لمجلد ا مجلة إبن الهيثم للعلوم الصرفة و التطبيقية Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 29 (1) 2016 ∆ ° ∆ ° ∆ °   (17) And the standard enthalpy of adsorption can be calculated on basis of the van't Hoff formula, ∆ °   (18) A plot of versus gives a straight line as shown in Figure (7) . The slope of the straight line is equal to- ∆ ° the negative values of ° reveals that the adsorption oh inhibitor molecules is an exothermic process (for methionine and lysine) and endothermic for glutamic acid. Generally an exothermic adsorption process suggests either physisorption or chemisorption while endothermic process is attributed to chemisorption. The unshared electron pairs in investigated molecules may interact with d-orbitals of Al alloy to provide a protective chemisorbed film[19]. The values of ∆ ° in the presence of the inhibitor are negative that is accompanied with exothermic adsorption process. ∆ ° of inhibition process can be calculated from equation(19). According to[18]. ∆ ° ∆ ° ∆ °   (19) 80 | Chemistry 2016) عام 1العدد ( 29لمجلد ا مجلة إبن الهيثم للعلوم الصرفة و التطبيقية Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 29 (1) 2016 References 1. Sainsbury, E.E. and Buchanan, R.A. (2000), "Fundamentals of electrochemical corrosion", ASM International Materials Park, USA. 2. Christia vargel (2004), "Corrosion of Aluminum", Elsevier ltd, new York. 3. Ating, E.I.; Umorenm, S.A; Udousoro, I.I; Ebenso, EE. and Udoh, A.P. (2010), "leaves extract of Ananas sativum as green corrosion inhibitor for aluminium in hydrochloric acid solution", green Chemical let rev. 3, 61-68. 4. Nnanna, L.A.; Anozie, I.U.; voaja, A.G.I. and Akoma, C.S., (2011) "comparative study of corrosion inhibition of aluminium alloy of type AA 3003 in acidic and alkalin media by Euphorbia hirta extract" Afr.J. pur Appl. Chem. 5, 265-271. 5. Obi-Egbed, N.O.; Obot, and Umoren, S.A. (2012) "Spondias mombin L.as a green corrosion inhibitor for aluminium in sulphuric acid: correlation between inhibitive effect and electronic properties of extracts major constituents using density functional theory", Arabain Journal of chemistry 5, 361-373. 6. Deepa prabhu, padmalatha and Roo, (2013), "Corrosion Inhibitor of 6063 aluminium alloy by cariandrum sativum L.seed extract in phosphoric acid medium". J. mater. Environ. Sci, 4, 732-742. 7. Founds, A. S.; Ahmed Abdel nazzer and Ashour, E.A (2011), "Amino acids as environmentally-friendly corrosion inhibitors for CuNi alloy in sulfide-polluted salt water", ZASTIIA MATERI JALA 52 broj 1. 8. Refat Hassan, ishaq zaafarany, Adil Gobouri and Hideo takagi, (2013), "ARevisit to the corrosion Inhibitor of Aluminium in Aquenous Alkaline solutions by vilater – soluble Alginates and pectates As Anionic Polyelectroyte inhibitors", Int. J. of corros, Artiicle under press. 9. Ladler, K.I., (1963), "Reaction kinetics", vol.1, pergmon Aess, new york, NY, USA ist edition. 10. Glasstone, S.; laidler, K.I.; and Erying ,H. (1941) "the theory of rate process", Mc Graw. Hill NewYork, NYUSA,. 11. Sinko,P.J.,(2000),"Physical chemical and biopharmaceuticals principles in pharmaceutical science", 5th edition USA, p.413. 12. Scendo, M.; radek, N.; and trela, J., (2012). "Corosion Inhibition of carbon steel in Acid chloride solution Schiff base of N-(2-chlorobenzylicdene -4- acetylanline)", Coros. rev. 30-33. 13. Tabi, F.EL.; Fouda, A.S., and Radwan, M.S., (2011), "Inhibitive effect of some thiadiazole derivatives on steel corrosion in neutral sodium hydroxide solution". Mater. chem. Phys. 26, 125. 14. Keles, H.; keles, M. ;Dehri I. and serinday, O. (2008) "Adsorption and inhibitor properties of amino phenyl and its schiff base on mild steel corrosion in 0.5 MHCl medium", colloids and surfaces A, 320, no 1-3 pp 138-145. 15. Amin, M.A.; Ibrahim, M.A., (2011) "thaidiazoles as corrosion inhibitors for carbon steel in solution", Corros, sci. 53, 873. 16. Ahmad, I.;Prasd, R., and Quraishi A.M., (2010), "Inhibition of mild steel corrosion in acid solution by pheniramine durg, Experimental and theoretical study", corros . Sci 52, 3033. 17. Deny, S.; X. L I H. Fu (2011), "A dsorption and inhibitive action of erhanal extracts chlomolaena adoratal for the corrosion of mild steel in solution", Corros. Sci. 53, 822. 18. Murguleseu, L.G., and Rodovie, O., (1961), " metal corrosion", int. conger 10-15 Aprial , London p.202-205. 19. Fouda, A.S.; Hassan, A.F.; Elmorsi, M.A; Fayed, T.A. and Abdelhakim, A., (2014). "Chalcones as environmentally. Friendly corrosion inhibition for SS Type 304 in IM HCL solution" Int. J. ELectrochem. Sci, q.pp 1298-1320. 81 | Chemistry 2016) عام 1العدد ( 29لمجلد ا مجلة إبن الهيثم للعلوم الصرفة و التطبيقية Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 29 (1) 2016 Table (1): The chemical composition of aluminium Alloy 2024 Si Fe Cu Mn Mg Cr Ni Zn V 0.099 0.26 4.46 0.58 1.43 0.01 0.01 0.06 0.016 Table (2): Data of polarization curve of corrosion of aluminium alloy 2024 in . . solution at pH (13) over the temperature range (293-308)K T/K i μA.cm E mv⁄ b mv⁄ . decade b mv⁄ . decade weight loss g.m .day Penetration loss/mm.year 293 1750 1320 162.6 573.7 141 19.1 298 2510 1347 179.2 378.3 202 27.3 303 2670 1359 122.8 310.9 216 29.1 308 3490 1320 210.5 379.6 281 38 Table (3): Activation energy , pre exponential (A) and entropy of activation ∆ ∗ for aluminium alloy 2024 corrosion in Solution in pH=13. . . ∆ ∗ . . / 17.5 123.5 19046398 10 Table (4): Values of , and inhibitors effeiciienly concentrations of methionine at temperature range (293-300) in pH=13. T/K Inhibition conc. mol.dm E mv⁄ i mA⁄ . cm θ IE % from i 293 0 1320 1750 - - 1 10 1348.5 548 0.69 69 5 10 1346 469 0.73 73 1 10 1300 367 0.79 79.1 298 0 1347 2500 - - 1 10 1352 799 0.68 68 5 10 1347 707 0.71 71.7 1 10 1339 459 0.78 78.1 303 0 1359 2670 - - 1 10 1340 897 0.67 67 5 10 1340 835 0.69 69 1 10 1316 716 0.73 73.3 308 0 1320 3490 - - 1 10 1335 1220 0.65 65.1 5 10 1436.5 1200 0.66 66 1 10 1301 986 0.71 71.8 82 | Chemistry 2016) عام 1العدد ( 29لمجلد ا مجلة إبن الهيثم للعلوم الصرفة و التطبيقية Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 29 (1) 2016 Table (5): Values of , and inhibitors efficiency concentrations of Lysine at temperature range (293-308) in pH=13. T/K Inhibition conc. mol.dm E mv⁄ i mA⁄ . cm θ IE % from i 293 0 1320 1750 - - 1 10 1344 489 0.72 72.1 5 10 1366 473 0.73 73 1 10 1347 451 0.74 74.3 298 0 1347 2500 - - 1 10 1325 718 0.713 71.3 5 10 1327 696 0.72 722 1 10 1354 688 0.725 75.5 303 0 1290 2670 - - 1 10 1290 801 0.70 70.2 5 10 1293 770 0.71 71 1 10 1275 765 0.715 71.5 308 0 1320 3490 - - 1 10 1295 1100 0.685 68.5 5 10 1290 1070 0.69 69 1 10 1287 1040 0.714 71.4 Table (6): Values of , and inhibitors efficiency percent concentrations of Glutamic acid at temperature range (293-308) in pH=13. T/K Inhibition conc. mol.dm E mv⁄ i mA⁄ . cm θ IE % from i 293 0 1320 1750 - - 1 10 1328 480 0.73 72.6 5 10 1300 460 0.74 73.4 1 10 1336 344 0.804 80.4 298 0 1347 2500 - - 1 10 1296 701 0.72 72 5 10 1419 658 0.737 73.7 1 10 1287 519 0.79 79.4 303 0 1359 2670 - - 1 10 1318 780 0.71 71 5 10 1321 723 0.73 73.1 1 10 1302 635 0.76 76.4 308 0 1320 3490 - - 1 10 1286 1030 0.705 70.5 5 10 1289 949 0.729 72.9 1 10 1269 870 0.75 75.1 83 | Chemistry 2016) عام 1العدد ( 29لمجلد ا مجلة إبن الهيثم للعلوم الصرفة و التطبيقية Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 29 (1) 2016 Table (7): Activation energy , pre exponential (A) and entropy of activation ∆ ∗ for the corrosion of AA 2024 in . . solution and different concentration of L-methionine, L.glutamic acid L-lysine. Inhibition conc.of inhibition mol.dm E KJ .mol⁄ ∆S∗J.K.mol A/ molecule cm .S L -m et h 1 10 30. 4 95 602300000 10 5 10 37.72 66.69 18612849390 10 1 10 44 47.88 181891692100 10 L -g lu 1 10 34.2 78.72 4333241195 10 5 10 38 57.38 57519203460 10 1 10 46.74 39.9 478423895800 10 L -l y s 1 10 34.77 77.14 5245813702 10 5 10 38 65.93 19046398350 10 1 10 40.47 58.9 47842389580 10 Table (8): Equilibrium constant adsorption/desorption standard free energy enthalpy and entropy of adsorption onto AA 2024 in . . solution in the presence of three amino acids L-methionine, L-glutamic acid L-lysine. / . ∆ ∗ . . ∆ ∗ . . ∆ . . . L - m et h io n in e 293 2500 28.8 -94.62 42.1 298 1250 27.6 41.0 303 026 28.3 39.9 308 384 25.5 39.0 L - g lu ta m ic a ci d 293 2500 28.79 28.19 20 298 2000 28.73 18 303 1666 28.67 16 308 1428 28.12 3.0 L -l y si n e 293 909 26.34 -15.90 36.0 298 769 26.22 34.6 303 714 26.61 35.3 308 666 26.84 35.5 84 | Chemistry 2016) عام 1العدد ( 29لمجلد ا مجلة إبن الهيثم للعلوم الصرفة و التطبيقية Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 29 (1) 2016 Figure (1): Polarization curves of 2024 AA corrosion pH=13 with . . NaCl solution at four temperatures in the range of (293-308)K.     Figure(2): Arrhenius Plot relating Log to 1/T for the 2024 AA corrosion pH=13 with . . NaCl solution at four temperatures in the range of (293-308)K. 0.32 0.33 0.33 0.33 0.33 0.33 0.34 0.34 0.34 0.34 1/T 3.34 3.36 3.38 3.40 3.42 3.44 3.46 Y = -5.97071 * X + 5.39505 85 | Chemistry 2016) عام 1العدد ( 29لمجلد ا مجلة إبن الهيثم للعلوم الصرفة و التطبيقية Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 29 (1) 2016 . . . . P o te n ti a l/ m V v s. S C E P o te n ti a l/ m V v s. S C E Current density/ . Current density/ . . . P o te n ti a l/ m V v s. S C E Current density/ . Figure (3): Polarization curves of 2024 AA corrosion in . . solution in pH=13 over the temperature range (293-308)K with three concentration of L- methionine , . . . . . P o te n ti a l/ m V v s. S C E P o te n ti a l/ m V v s. S C E Current density/ . Current density/ . . . P o te n ti a l/ m V v s. S C E Current density/ . Figure (4): Polarization curves of 2024 AA corrosion in . . solution in pH=13 over the temperature range (293-308)K with three concentrations of L-Glutamic acid , . . . . . 0.1 1.0 10.0 100.0 1000.0 -1550 -1500 -1450 -1400 -1350 -1300 -1250 -1200 -1150 -1100 293K 298K 303K 308K 0.0 0.1 1.0 10.0 100.0 -1550 -1500 -1450 -1400 -1350 -1300 -1250 -1200 -1150 -1100 293K 298K 303K 308K 0.1 1.0 10.0 100.0 -1650 -1600 -1550 -1500 -1450 -1400 -1350 -1300 -1250 -1200 293K 298K 303K 308K 0.1 1 10 100 -1550 -1500 -1450 -1400 -1350 -1300 -1250 -1200 -1150 -1100 293K 298K 303K 308K 0.01 0.1 1 10 100 -1600 -1550 -1500 -1450 -1400 -1350 -1300 -1250 -1200 -1150 -1100 293K 298K 303K 308K 0.01 0.1 1 10 100 -1550 -1500 -1450 -1400 -1350 -1300 -1250 -1200 -1150 -1100 -1050 293K 298K 303K 308K 86 | Chemistry 2016) عام 1العدد ( 29لمجلد ا مجلة إبن الهيثم للعلوم الصرفة و التطبيقية Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 29 (1) 2016 P o te n ti a l/ m V v s. S C E P o te n ti a l/ m V v s. S C E Current density/ . Current density/ . 0.01 . P o te n ti a l/ m V v s. S C E Current density/ . Figure (5): Polarization curves of 2024 AA corrosion in . . solution in pH=13 over the temperature range (293-308)K with three concentrations of L-lysine , . . . . . . . Figure (6): Langmuir adsorption plots of three amino acid onto 2024AA in . . solution of various temperatures at pH value (pH=13) 0.01 0.1 1 10 100 -1550 -1500 -1450 -1400 -1350 -1300 -1250 -1200 -1150 -1100 293K 298K 303K 308K 0.1 1 10 100 1000 -1550 -1500 -1450 -1400 -1350 -1300 -1250 -1200 -1150 -1100 293K 298K 303K 308K 0.01 0.1 1 10 100 1000 -1550 -1500 -1450 -1400 -1350 -1300 -1250 -1200 -1150 -1100 293K 298K 303K 308K 0.000 0.002 0.004 0.006 0.008 0.010 C 0.000 0.002 0.004 0.006 0.008 0.010 0.012 0.014 293K 298K 303K 308K 0.000 0.002 0.004 0.006 0.008 0.010 0.000 0.002 0.004 0.006 0.008 0.010 0.012 0.014 293K 298K 303K 308K 0.000 0.002 0.004 0.006 0.008 0.010 C 0.000 0.002 0.004 0.006 0.008 0.010 0.012 293K 298K 303K 308K 87 | Chemistry 2016) عام 1العدد ( 29لمجلد ا مجلة إبن الهيثم للعلوم الصرفة و التطبيقية Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 29 (1) 2016 Ln     Figure (7): Van't Hoff plot of 2024AA in . . solution containing three amino acids of various temperatures at pH value (13)   a. Polished 2024 AA b. After immersion in the corrosive medium   c. After immersion in the corrosive medium + L-methionine d. After immersion in the corrosive medium + L-Glutamic acid e. After immersion in the corrosive medium + L-lysine Figure (8): Optical microscope micrographs of 2024AA surface in pH=13. 292 294 296 298 300 302 304 306 308 1/T 5.5 6.0 6.5 7.0 7.5 8.0 8.5 METH, Y = -0.126198 * X + 44.7585 GLU, Y = -0.037 * X + 18.636 LYS, Y = -0.0212 * X + 13.0156 88 | Chemistry 2016) عام 1العدد ( 29لمجلد ا مجلة إبن الهيثم للعلوم الصرفة و التطبيقية Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 29 (1) 2016 في 2024سبيكة االلمنيوم ماض االمينية كمثبطات صديقة للبيئة لتآكلاالح المحيط القاعدي عبد العزيز عيسىوصال زينب وجدي احمد قسم الكيمياء / كلية التربية للعلوم الصرفة (ابن الهيثم) / جامعة بغداد 2015حزيران //23 :،قبل في 2015مارس//24استلم في: الخالصة 13في محلول قاعدي 2024يتناول موضوع البحث دراسة كهروكيميائية لسلوك تآكل سبيكة االلمنيوم 0.6 لكلوريد الصوديوم بتركيز بغياب وجود تراكيز مختلفة من االحماض االمينية الثالثة (ميثونين . K 293وحامض الكلوتاميك والالسين) كمثبطات صديقة للبيئة على مدى درجات الحرارة اشتملت الدراسة 308 لساكن والمجهر الضوئي.على طريقة االستقطاب الكهروكيميائي بأستعمال جهاز المجهاد ا وجد إن كفاءة التثبيط تزداد بزيادة تركيز المثبط وتقل بزيادة درجة الحرارة. وجد ان اعلى قيمة لكفاءة المثبط وجدت مع 0.10وبتركيز المثبط 293عند 80.4الاليسين . اظهرت النتائج ان التثبيط يحدث من خالل . Langmuir Isotherm forعلى سطح الفلز ووجد انها تتبع مسار درجة الحرارة لالنكمير (أمتزاز جزيئات المثبط Adsorption لتوضيح وطاقة التنشيط ∆) وقد تم حساب بعض المعلومات الثرموديناميكية طاقة جبس ميكانيكية تثبيط التآكل. اقترضت –لمات الحركية حسبت باستعمال نظرية أرينيوس قياسات االستقطاب اوضحت بأن المثبط من نوع المختلط المع في المحيط القاعدية وقد تم تمييز سطح الفلز قبل وبعد التثبيط باستعمال المجهر 2024ميكانية مناسبة لتآكل سبيكة االلمنيوم الضوئي. لالمتزاز, ميكانيكية االمتزاز ., حوامض امينية, طاقة جبس الحرة 2024: تثبيط التآكل, سبيكة الكلمات المفتاحية