N.V.Lakshmi, S.Karthikeyan, N.Arivazhagan
Keywords: Corrosion, Azithromycin, Aluminium 2024, Quantum chemical
Abstract:
The significance of Azithromycin (AZ) on corrosion of aluminium alloy 2024 in 0.1N Hydrochloric acid was examined using weight loss measurements, Tafel polarization studies and scanning electron microscopy. The results indicated that AZ is a good inhibitor for aluminium alloy in 0.1N HCl and maximum efficiency obtained was 91% at 450ppm concentration of azithromycin. Potentiostatic Polarization analyses displayed that AZ works as a mixed type of inhibitor. Electrochemical impedance plots were used to examine the mechanism of corrosion. Quantum chemical studies were done for azithromycin and its various quantum chemical parameters were calculated and tabulated.
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1ISSN 1466-8858 Volume 17, Preprint 7 submitted 4 February 20141 ©1(MD)1jniversity1of1Janchester1and1the1authors61Δhis1is1a1preprint1of1a1paper1that1has1been1submitted1for1publication1in1the1+ournal1of1 8orrosion1øcience1and1Wngineering61-t1will1be1reviewed1andU1subject1to1the1reviewers"1commentsU1be1published1online1at1 http%33www6jcse6org1in1due1course61jntil1such1time1as1it1has1been1fully1published1it1should1not1normally1be1referenced1in1published1work61 1 AzithromycinAzithromycinAzithromycinAzithromycin :::: A Potential Corrosion inhibitor for A Potential Corrosion inhibitor for A Potential Corrosion inhibitor for A Potential Corrosion inhibitor for Aluminum 2024 Aluminum 2024 Aluminum 2024 Aluminum 2024 in acidic mediumin acidic mediumin acidic mediumin acidic medium N.V.Lakshmi N.V.LakshmiN.V.LakshmiN.V.Lakshmi 1111,,,, S.KarthikeyanS.KarthikeyanS.KarthikeyanS.Karthikeyan1*1*1*1*, N.Arivazhagan, N.Arivazhagan, N.Arivazhagan, N.Arivazhagan2222 1 Surface Engineering Research lab, CNBT, VIT University, Vellore -632014, India 2 Manufacturing Division, School of Mechanical and building Sciences, VIT University, Vellore -632014, India Abstract AbstractAbstractAbstract The significance of Azithromycin (AZ) on corrosion of aluminium alloy 2024 in 0.1N Hydrochloric acid was examined using weight loss measurements, Tafel polarization studies and scanning electron microscopy. The results indicated that AZ is a good inhibitor for aluminium alloy in 0.1N HCl and maximum efficiency obtained was 91% at 450ppm concentration of azithromycin. Potentiostatic Polarization analyses displayed that AZ works as a mixed type of inhibitor. Electrochemical impedance plots were used to examine the mechanism of corrosion. Quantum chemical studies were done for azithromycin and its various quantum chemical parameters were calculated and tabulated. Keywords: Keywords:Keywords:Keywords: Corrosion, Azithromycin, Aluminium 2024, Quantum chemical 1. Introduction 1. Introduction1. Introduction1. Introduction The Aluminium alloy 2024 is largely used in aerospace industries because of its ideal weight to strength ratio. The high strength of the alloy 2024 is due the presence of alloying element predominantly copper and this makes alloy more prone to localized corrosion due to discrimination of the intermetallic particles in grain boundaries [1- 2].Generally hydrochloric acid is used for pickling, chemical and electrochemical etching of Al. Numerous methods are used to shrink the corrosion rate of metals in 1* corresponding author (skarthikeyanphd@yahoo.co.in)1* corresponding author (skarthikeyanphd@yahoo.co.in)1* corresponding author (skarthikeyanphd@yahoo.co.in)1* corresponding author (skarthikeyanphd@yahoo.co.in) 1ISSN 1466-8858 Volume 17, Preprint 7 submitted 4 February 20141 ©1(MD)1jniversity1of1Janchester1and1the1authors61Δhis1is1a1preprint1of1a1paper1that1has1been1submitted1for1publication1in1the1+ournal1of1 8orrosion1øcience1and1Wngineering61-t1will1be1reviewed1andU1subject1to1the1reviewers"1commentsU1be1published1online1at1 http%33www6jcse6org1in1due1course61jntil1such1time1as1it1has1been1fully1published1it1should1not1normally1be1referenced1in1published1work61 2 acids, and in the midst of different methods practice of inhibitor is utmost common. Many organic compounds were used as corrosion inhibitor [3-7]. But currently use of antibiotics as corrosion inhibitors is increased tremendously because of less toxicity and eco-friendly nature. Heterocyclic compounds holding hetro atoms such as sulphur, nitrogen and oxygen atoms comprising multiple bonds adsorb on the metal surface and thus act as active corrosion inhibitor for aluminium 2024 in acid medium [8-13]. A meticulous examination was used to explore the inhibition properties of azithromycin. The corrosion inhibiting capability of azithromycin might be due to its arrangement of atoms. Various studies demonstrate that azithromycin is prospective corrosion inhibitor. Azithromycin is an active antibiotic used for treat bacterial and respiratory tract infections which falls under the class of azalide, which is a subclass of macrolide antibiotics. 2. 2. 2. 2. ExpExpExpExperimental Detailserimental Detailserimental Detailserimental Details 2.1 2.12.12.1MaterialsMaterialsMaterialsMaterials and methodsand methodsand methodsand methods Materials employed for the analyses were Aluminium 2024 sheet of compositions (wt. %), Cu (4.3), Mn (0.5), Mg (1.3) and appreciable amount of Si, Zn, Ni, Cr in addition to Al balance. The sheet was then cut into number of sample of each 4 x 1 x 3 cm dimensions were used for weight loss and electrochemical studies. Each sample was mechanically polished followed by degreasing with acetone then washed with double distilled water and finally dried. Electrochemical experiments were conducted in three electrode cell assembly with Al as working electrode. Platinum wire as counter and Ag/Agcl/kcl (sat) as reference electrode.AR grade Hydrochloric acid and double distilled water are used to make 0.1N HCl for all experimentations. 1ISSN 1466-8858 Volume 17, Preprint 7 submitted 4 February 20141 ©1(MD)1jniversity1of1Janchester1and1the1authors61Δhis1is1a1preprint1of1a1paper1that1has1been1submitted1for1publication1in1the1+ournal1of1 8orrosion1øcience1and1Wngineering61-t1will1be1reviewed1andU1subject1to1the1reviewers"1commentsU1be1published1online1at1 http%33www6jcse6org1in1due1course61jntil1such1time1as1it1has1been1fully1published1it1should1not1normally1be1referenced1in1published1work61 3 2.2 Inhibitor2.2 Inhibitor2.2 Inhibitor2.2 Inhibitor The antibiotic namely azithromycin was purchased from corresponding manufacturer and used without further purification. The structure of azithromycin is shown in fig 1.AZ contains methyl substituted nitrogen atom incorporated into the lactone ring, thus making the lactone ring 15 membered. With this structure it is likely to act as good inhibitor. FIG 1 Structure of Azithromycin FIG 1 Structure of Azithromycin FIG 1 Structure of Azithromycin FIG 1 Structure of Azithromycin 2.3 Weight loss 2.3 Weight loss 2.3 Weight loss 2.3 Weight loss studiesstudiesstudiesstudies The inhibitor was initially screened by a weight loss method [12].various samples Al were submerged in 0.1 N HCl solution comprising diverse concentrations of inhibitors (AZ).Samples were weighed before and after immersion and weight loss was estimated. The surface coverage () and inhibition efficiency were determined by means of following equations. Surface coverage () = Wo-W/Wo Inhibition efficiency (%) = W o-W/Wo X 100 Where, W o - Weight loss without inhibitor O N O OH OO O O OH O OH N OHOH 1ISSN 1466-8858 Volume 17, Preprint 7 submitted 4 February 20141 ©1(MD)1jniversity1of1Janchester1and1the1authors61Δhis1is1a1preprint1of1a1paper1that1has1been1submitted1for1publication1in1the1+ournal1of1 8orrosion1øcience1and1Wngineering61-t1will1be1reviewed1andU1subject1to1the1reviewers"1commentsU1be1published1online1at1 http%33www6jcse6org1in1due1course61jntil1such1time1as1it1has1been1fully1published1it1should1not1normally1be1referenced1in1published1work61 4 W - Weight loss using varied concentrations of inhibitors 2.4 Tafel polarization studies 2.4 Tafel polarization studies2.4 Tafel polarization studies2.4 Tafel polarization studies Tafel Polarization studies were carried out in a conventional three - electrode cylindrical glass cell, using CH electrochemical analyzer (Model660E). Before to computing the polarization graphs the solution was deaerated for 20 min. and the working electrode was sustained at its corrosion potential for 10 min for attaining a steady state. The Al 2024 surface was bare to different concentrations of azithromycin in 100mL of 0.1N HCl at room temperature. The inhibition efficiency (IE %) was estimated using the equation Inhibition Efficiency (IE %) = (I 0 -I /I0) X 100 Where I 0 and I are the corrosion current density in absence and presence of inhibitor respectively. The current-potential curves were documented by altering the electrode potential from -750mV to +150mV versus the open circuit potential. The resultant corrosion current (I corr) was recorded. Tafel plots were made by plotting E versus log I. Corrosion Potential (E corr), corrosion current density (I corr) and cathodic (βc) and anodic slopes (βa) were intended from known procedures. 2.5 2.52.52.5. Impedance. Impedance. Impedance. Impedance studiesstudiesstudiesstudies Impedance studies were carried out in the frequency range from 0.1 to 10000 Hz using amplitude of 20 mV and 10 mV peak to peak with an AC signal at the open-circuit potential .The impedance graphs were schemed in the nyquist representation. Charge transfer resistance (R ct) values were acquired by subtracting the high-frequency impedance. The inhibition efficiency was obtained from the equation: Inhibition Efficiency (IE %) = (R ct - Rct / Rct) x 100 1ISSN 1466-8858 Volume 17, Preprint 7 submitted 4 February 20141 ©1(MD)1jniversity1of1Janchester1and1the1authors61Δhis1is1a1preprint1of1a1paper1that1has1been1submitted1for1publication1in1the1+ournal1of1 8orrosion1øcience1and1Wngineering61-t1will1be1reviewed1andU1subject1to1the1reviewers"1commentsU1be1published1online1at1 http%33www6jcse6org1in1due1course61jntil1such1time1as1it1has1been1fully1published1it1should1not1normally1be1referenced1in1published1work61 5 Where R"ct and Rct are the corrosion current of Aluminum 2024 with and without treatment of inhibitor respectively. 2.6 Surface Morphology studies2.6 Surface Morphology studies2.6 Surface Morphology studies2.6 Surface Morphology studies The Scanning electron microscopies (SEM) Model: S-3000H, Hitachi, Japan, was used to observe the specimen"s surface which is dipped in 0.1 N hydrochloric acid and with inhibitor solutions [15]. 2.7 Theoretical 2.7 Theoretical 2.7 Theoretical 2.7 Theoretical AnalysisAnalysisAnalysisAnalysis Quantum studies were done using MOPAC 2000 program of CS Chemoffice packet program. The highest occupied molecular orbital (HOMO)energy, lowest unoccupied molecular orbital (LUMO) energy, Dipole moment (?), hardness(η), absolute softness(σ) and total energy of the molecule were intended with the above given software package. 3 333. RESULTS AND DISCUSSION. RESULTS AND DISCUSSION. RESULTS AND DISCUSSION. RESULTS AND DISCUSSION 3.1 3.1 3.1 3.1 weight loss weight loss weight loss weight loss StudiesStudiesStudiesStudies The values of inhibition efficiency (IE %) and the rate of corrosion from weight loss studies at diverse concentrations of azithromycin are précised in table-1. It displays that the compound successfully inhibits the corrosion of aluminium alloy 2024 in 0.1 N HCl medium. Extreme inhibition efficiency and decreased corrosion rate is due to the influence of amplified adsorption and enlarged coverage of inhibitor on aluminium surface with growth in the inhibitor concentration. The corrosion inhibition by azithromycin may possibly be due to the following interactions: 1. The interaction between the lone pairs of electrons on exo oxygen and nitrogen atoms. 1ISSN 1466-8858 Volume 17, Preprint 7 submitted 4 February 20141 ©1(MD)1jniversity1of1Janchester1and1the1authors61Δhis1is1a1preprint1of1a1paper1that1has1been1submitted1for1publication1in1the1+ournal1of1 8orrosion1øcience1and1Wngineering61-t1will1be1reviewed1andU1subject1to1the1reviewers"1commentsU1be1published1online1at1 http%33www6jcse6org1in1due1course61jntil1such1time1as1it1has1been1fully1published1it1should1not1normally1be1referenced1in1published1work61 6 2. The interactions between unshared electron pairs in azacyclopenta-decane15-one ring along with eight electron releasing methyl groups with positively charged aluminium surface. 3.2 3.2 3.2 3.2 PotentiPotentiPotentiPotentiodynamic polarizationodynamic polarizationodynamic polarizationodynamic polarization studiesstudiesstudiesstudies -0.9 -0.8 -0.7 -0.6 -0.5 -7-6-5-4-3-2-10 50ppm Ewe/V vs SCE log I/mA 150ppm250ppm350ppm450ppm blank 1ISSN 1466-8858 Volume 17, Preprint 7 submitted 4 February 20141 ©1(MD)1jniversity1of1Janchester1and1the1authors61Δhis1is1a1preprint1of1a1paper1that1has1been1submitted1for1publication1in1the1+ournal1of1 8orrosion1øcience1and1Wngineering61-t1will1be1reviewed1andU1subject1to1the1reviewers"1commentsU1be1published1online1at1 http%33www6jcse6org1in1due1course61jntil1such1time1as1it1has1been1fully1published1it1should1not1normally1be1referenced1in1published1work61 7 FIG 2 FIG 2FIG 2FIG 2 Tafel curves of Aluminium alloy 2024 in 0.1N HCl at various concentrations of Azithromycin Tafel curves for aluminum alloy 2024 in HCl medium at various concentrations of azithromycin are presented in figure-2. The parameters such as corrosion potential (E corr ), current densities (I corr), anodic tafel slopes (βa) and cathodic tafel slopes (βc) and inhibition efficiency were studied from Tafel polarization curves as a function azithromycin concentration are displayed in table- 2. It can be realized from the table that values of Tafel slopes and I corr are very much diminished in contrast to the metal surface without inhibitor. It is also revealed that growing the concentrations of azithromycin amplifies the β a and βc in imbalanced fashion approving that the inhibition of corrosion of Al alloy in HCl medium is in mixed control [14-16]. Values of E corr are progressed to less negative values in the existence of different concentrations of AZ. This might be the cause for developing resolutely adherent adsorbed film of AZ on the Aluminum alloy. It marked that most of the values of inhibition efficiency found by weight loss procedures and Tafel polarization method are with virtuous agreement. 3.4 Impedance studies 3.4 Impedance studies3.4 Impedance studies3.4 Impedance studies The Nyquist illustrations of impedance performance of aluminium alloy 2024 in acidic medium with and without azithromycin is used to compute charge transfer resistance (R t )and double layer capacitance (Cdl) values which are tabularized in table-3. From the table, it is found that values of R ct increases at the expenditure of double layer capacitance with growth in AZ concentration [17]. This contributes to the improved adsorption of the AZ antibiotic on the Al alloy surface with intensification of drug concentration. 1ISSN 1466-8858 Volume 17, Preprint 7 submitted 4 February 20141 ©1(MD)1jniversity1of1Janchester1and1the1authors61Δhis1is1a1preprint1of1a1paper1that1has1been1submitted1for1publication1in1the1+ournal1of1 8orrosion1øcience1and1Wngineering61-t1will1be1reviewed1andU1subject1to1the1reviewers"1commentsU1be1published1online1at1 http%33www6jcse6org1in1due1course61jntil1such1time1as1it1has1been1fully1published1it1should1not1normally1be1referenced1in1published1work61 8 A plot of surface coverage (ø) against log C exhibited a straight line plot endorsing that the adsorption of AZ on Al alloy surface from HCl medium followed Temkins adsorption isotherm. This is main confirmation to corrosion inhibition of azithromycin, as a consequence of its adsorption on the aluminum surface. 3.5 Quantum chemical studies:3.5 Quantum chemical studies:3.5 Quantum chemical studies:3.5 Quantum chemical studies: FIG 4 FIG 4FIG 4FIG 4.a. HOMO OF AZ .a. HOMO OF AZ .a. HOMO OF AZ .a. HOMO OF AZ FIG 4FIG 4FIG 4FIG 4.b. LUMO OF AZ.b. LUMO OF AZ.b. LUMO OF AZ.b. LUMO OF AZ The quantum chemical aspects such as highest occupied molecular orbital (EHOMO) energy, lowest unoccupied molecular orbital (E LUMO) energy, LUMO- HOMO, energy gap (ΔE), dipole moment (?), [18-21] are summarized in table -4 and in figure 4 a and 4.b. Azithromycin revealed greater inhibition efficiency due to its improved dipole moment values by the existence of electron receiving lactones and N-Oxime groups with unshared electron pairs on nitrogen . A peculaity in HOMO and LUMO values were noted.Both energy orbitals are showing almost similar distribution of electrons on the 1ISSN 1466-8858 Volume 17, Preprint 7 submitted 4 February 20141 ©1(MD)1jniversity1of1Janchester1and1the1authors61Δhis1is1a1preprint1of1a1paper1that1has1been1submitted1for1publication1in1the1+ournal1of1 8orrosion1øcience1and1Wngineering61-t1will1be1reviewed1andU1subject1to1the1reviewers"1commentsU1be1published1online1at1 http%33www6jcse6org1in1due1course61jntil1such1time1as1it1has1been1fully1published1it1should1not1normally1be1referenced1in1published1work61 9 atoms being responsible for adsorbtion. It is evident that , If the values of ΔE is above 2, the adsorption of inhibitors will be effective on steel surface. 3.6 Scanning electron microscopy:3.6 Scanning electron microscopy:3.6 Scanning electron microscopy:3.6 Scanning electron microscopy: SEM micrographs are communicative of the modifications that complement both corrosion and defense of the Aluminium alloy in acidic environment [22]. Figure-5 shows the SEM of Al alloy in 0.1N HCl, which illustrates cracks, random grooves signifying the injury produced to the alloy surface by HCl. Figure-6 spectacles SEM images of aluminium alloy treated with 0.1 N HCl comprising 450pm of AZ, screening the look of layered surface along with nonappearance of unsystematic grooves marked the adsorption of azithromycin on Al alloy 2024. FIG FIG FIG FIG 5 5 5 5 Scanning electron microscopy Scanning electron microscopy Scanning electron microscopy Scanning electron microscopy of Alof Alof Alof Al alloy 2024alloy 2024alloy 2024alloy 2024 dippdippdippdippedededed in 0.1N in 0.1N in 0.1N in 0.1N HClHClHClHCl 1ISSN 1466-8858 Volume 17, Preprint 7 submitted 4 February 20141 ©1(MD)1jniversity1of1Janchester1and1the1authors61Δhis1is1a1preprint1of1a1paper1that1has1been1submitted1for1publication1in1the1+ournal1of1 8orrosion1øcience1and1Wngineering61-t1will1be1reviewed1andU1subject1to1the1reviewers"1commentsU1be1published1online1at1 http%33www6jcse6org1in1due1course61jntil1such1time1as1it1has1been1fully1published1it1should1not1normally1be1referenced1in1published1work61 10 FIG FIG FIG FIG 6666 Scanning electron microscopy Scanning electron microscopy Scanning electron microscopy Scanning electron microscopy of Alof Alof Alof Al alloy 2024alloy 2024alloy 2024alloy 2024 dippdippdippdippedededed in 0.1N HClin 0.1N HClin 0.1N HClin 0.1N HCl using 450ppm using 450ppm using 450ppm using 450ppm of azithromycin of azithromycinof azithromycinof azithromycin 4. Conclusions 4. Conclusions4. Conclusions4. Conclusions 1. Azithromycin performs as worthy inhibitor for corrosion inhibition of aluminium alloy 2024 in acidic environment. 2. Tafel polarization investigation confirms that azithromycin is a mixed kind of inhibitor. 3. The azithromycin act as good inhibitor which is demonstrated from improved Rct and diminished C dl values. 5. SEM images established the development of defensive layer of AZ on Al alloy 2024. 6. The values of HOMO, LUMO, ΔE and ? resultant from quantum chemical studies validated the outcomes of chemical and electrochemical studies. R RRReeeeffffeeeerrrreeeennnncccceeeessss:::: 1. Highly effective organic corrosion inhibitors for 2024 aluminium alloy, S.Lamaka, M.Zheludkevich, K.Yasakau, Electrochimica acta, volume 52, pp. 7231-7247,2007 2. Antifungal drugs as corrosion inhibitors for aluminium in 0.1 M HCl 1ISSN 1466-8858 Volume 17, Preprint 7 submitted 4 February 20141 ©1(MD)1jniversity1of1Janchester1and1the1authors61Δhis1is1a1preprint1of1a1paper1that1has1been1submitted1for1publication1in1the1+ournal1of1 8orrosion1øcience1and1Wngineering61-t1will1be1reviewed1andU1subject1to1the1reviewers"1commentsU1be1published1online1at1 http%33www6jcse6org1in1due1course61jntil1such1time1as1it1has1been1fully1published1it1should1not1normally1be1referenced1in1published1work61 11I.B. Obot , N.O. Obi-Egbedi , S.A. Umoren, Corrosion science, volume 51, pp. 1868- 1875, 2009 3. Schiff bases as corrosion inhibitor for aluminium in HCl solution Serpil Safak , Berrin Duran , Aysel Yurt, Gulsen Turkoglu, Corrosion science, volume 54, pp. 251-259, 2012 4. The inhibitive effect of some tetrazole derivatives towards Al corrosion in acid solution: Chemical, electrochemical and theoretical studies, K.F. Khaled a,b, M.M. Al- Qahtani b, Materials chemistry and physics, volume 113, pp. 150-158, 2009 5. Effect of some organic inhibitors on the corrosion behavior of Cu-Fe and Cu-Al-Fe alloys in sulphuric acid solution, N.H. Hela, H.E. El-fifky, M.R. Negem, Journal of Corrosion Science &Engineering, Vol.10, 2006 6. Ethane-2- thioamido-4-amino-N-(5-methylisoxazol-3-yl)-benzene sulfonamide: A novel inhibitor for the corrosion of mild steel in 1N HCl , S. Karthikeyan, N. Arivazhagan, S. Narayanan, Journal of Corrosion Science &Engineering, Vol.16, 2013 7. Inhibition of acidic corrosion of pure aluminum by some organic compounds, A.K. Maayta , N.A.F. Al-Rawashdeh, Corrosion science, volume 46, pp. 1129-1140, 2004 8. Experimental and theoretical studies of cloxacillin on the corrosion of mild steel in 1M H 2SO4 S. Harikumar and S. Karthikeyan, Journal of corrosion science and engineering, Vol.16, 2013 9. Corrosion Inhibition performance of cetirizine on mild steel in 1m H2SO4, R.S.Dubey, K.U.Singh, Journal of Corrosion Science &Engineering, Vol.14, 2011 10. ... Antibacterial drugs as corrosion inhibitors for corrosion of aluminium in hydrochloric solution, M. Abdallah, Corrosion science, volume 46, pp 1981-1996, 2004 11.Torsemide and Furosemide as Green Inhibitors for the Corrosion of Mild Steel in Hydrochloric Acid Medium, S. Harikumar and S. Karthikeyan, Industrial and Engineering Chemistry Research, 52(22), pp. 7457-7469, 2013 1ISSN 1466-8858 Volume 17, Preprint 7 submitted 4 February 20141 ©1(MD)1jniversity1of1Janchester1and1the1authors61Δhis1is1a1preprint1of1a1paper1that1has1been1submitted1for1publication1in1the1+ournal1of1 8orrosion1øcience1and1Wngineering61-t1will1be1reviewed1andU1subject1to1the1reviewers"1commentsU1be1published1online1at1 http%33www6jcse6org1in1due1course61jntil1such1time1as1it1has1been1fully1published1it1should1not1normally1be1referenced1in1published1work61 12 12. Corrosion inhibition of aluminum 6063 using some pharmaceutical compounds, A.S. Fouda , A.A. Al-Sarawy , F.Sh. Ahmed c, H.M. El-Abbasy, Corrosion science, volume 51, pp. 485-492, 2009 13. Inhibition of mild steel corrosion in hydrochloric acid solution by cloxacillin drug, S. Harikumar and S. Karthikeyan, Journal of Materials and Environmental Studies, Vol.5, pp. 925-934, 2012 14. Mechanism of corrosion and its inhibition, K. Madhavan, PhD Thesis, Alagappa Uni versity, India, June 1996 15.Adsorption Characteristics and Corrosion Inhibitive Properties of Clotrimazole for Aluminium Corrosion in Hydrochloric Acid, I.B. Obot, N.O. Obi-Egbedi, S.A. Umoren, Int. J. Electrochem. Sci, Vol. 4, pp. 863-877, 2009 16.The effect of inhibitor on the corrosion of aluminum alloys in acidic solutions, R.Rosliza,W.Wan Nik, H.Senin, Materials chemistry and physics, volume 107, pp. 281- 288, 2008 17. The Structure of the Electrical Double Layer at the Metal Solution Interface, M.A. Devanathan, B. Til ak, Chem.Revs, 65, pp635, 1965 18. Gu Hough, Zhou Zhongbai, Tao Yingachu , Yao Luaw, Wahan Dauxe Xuebao, Ziran Kexuebaw, 2, pp57, 1982 19. G. Trabanelli and Zucchui F.Revon, Corrosion and coatings, 1, pp47, 1973 20. A.K. Lahiri, N.G. Banerjee, NML. Tech. Journal, 5, pp33, 1963 21. The use of quantum chemical methods in corrosion inhibitor studies, Gokhan Gece, corrosion science, volume 50, pp 2981-2992, 2008 22. Corrosion Inhibition of Mild Steel in 1M H2SO4 by Ampicillin as an Inhibitor, S. Harikumar and S. Karthikeyan, Journal of Corrosion Science &Engineering, Vol.16, 2013 1ISSN 1466-8858 Volume 17, Preprint 7 submitted 4 February 20141 ©1(MD)1jniversity1of1Janchester1and1the1authors61Δhis1is1a1preprint1of1a1paper1that1has1been1submitted1for1publication1in1the1+ournal1of1 8orrosion1øcience1and1Wngineering61-t1will1be1reviewed1andU1subject1to1the1reviewers"1commentsU1be1published1online1at1 http%33www6jcse6org1in1due1course61jntil1such1time1as1it1has1been1fully1published1it1should1not1normally1be1referenced1in1published1work61 13Table 1. Table 1. Table 1. Table 1. InInInInhibition efficiencyhibition efficiencyhibition efficiencyhibition efficiency, corrosion rate and surface , corrosion rate and surface , corrosion rate and surface , corrosion rate and surface coverage for the corrosion of coverage for the corrosion of coverage for the corrosion of coverage for the corrosion of aluminium aluminium aluminium aluminium alloy 2024 alloy 2024 alloy 2024 alloy 2024 in 0.1Nin 0.1Nin 0.1Nin 0.1N HCl HCl HCl HCl withwithwithwith different measures different measures different measures different measures of of of of azithromycin azithromycin azithromycin azithromycin gainedgainedgainedgained from from from from weight weightweightweight loss loss loss loss studiesstudiesstudiesstudies Concentration ConcentrationConcentrationConcentration (ppm)(ppm)(ppm)(ppm) Corrosion rate Corrosion rateCorrosion rateCorrosion rate (mgcm (mgcm(mgcm(mgcm----2222hhhh----1111) ) ) ) Inhibition Inhibition Inhibition Inhibition efficiency (IE %) efficiency (IE %)efficiency (IE %)efficiency (IE %) Surface coverage Surface coverageSurface coverageSurface coverage (((()))) Blank 50 150 250 350 450 0.01728 0.00864 0.00677 0.00485 0.00294 0.00161 - 50 61 72 83 91 - 0.5000 0.6082 0.7193 0.8298 0.9068 T TTTable 2able 2able 2able 2.... ElectrochemicalElectrochemicalElectrochemicalElectrochemical parameters of parameters of parameters of parameters of aluminiumaluminiumaluminiumaluminium alloy 2024 alloy 2024 alloy 2024 alloy 2024 in in in in 0.10.10.10.1NNNN HCl HCl HCl HCl with different with different with different with different measures measures measures measures of of of of azithromycin azithromycin azithromycin azithromycin from from from from Tafel Tafel Tafel Tafel polarization studies.polarization studies.polarization studies.polarization studies. Concentration Concentration Concentration Concentration of Inhibitor of Inhibitor of Inhibitor of Inhibitor ( (((ppmppmppmppm)))) E EEEcorr corr corr corr (mV) (mV)(mV)(mV) Tafel slopes in mV in dec Tafel slopes in mV in decTafel slopes in mV in decTafel slopes in mV in dec----1111 IIIIcorr corr corr corr mA cm mA cmmA cmmA cm----1111 Inhibition Inhibition Inhibition Inhibition efficiency efficiency efficiency efficiency (%) (%)(%)(%) ββββaaaa β βββcccc Blank 50 150 250 350 450 -0.821 -0.810 -0.801 -0.790 -0.780 -0.753 70 79 72 76 78 73 123 111 126 120 131 119 0.841 0.415 0.305 0.239 0.141 0.094 - 51 64 72 83 89 1ISSN 1466-8858 Volume 17, Preprint 7 submitted 4 February 20141 ©1(MD)1jniversity1of1Janchester1and1the1authors61Δhis1is1a1preprint1of1a1paper1that1has1been1submitted1for1publication1in1the1+ournal1of1 8orrosion1øcience1and1Wngineering61-t1will1be1reviewed1andU1subject1to1the1reviewers"1commentsU1be1published1online1at1 http%33www6jcse6org1in1due1course61jntil1such1time1as1it1has1been1fully1published1it1should1not1normally1be1referenced1in1published1work61 14 T TTTable able able able 3333....ElectrochemicalElectrochemicalElectrochemicalElectrochemical impedance impedance impedance impedance parametersparametersparametersparameters and its inhibition efficiency forand its inhibition efficiency forand its inhibition efficiency forand its inhibition efficiency for the the the the corrosion of corrosion of corrosion of corrosion of aluminium aluminium aluminium aluminium alloy 2024 alloy 2024 alloy 2024 alloy 2024 inininin 0.1N HCl0.1N HCl0.1N HCl0.1N HCl with different measures with different measures with different measures with different measures of of of of azithromycin. azithromycin.azithromycin.azithromycin. Table Table Table Table 4444: Quantum chemical : Quantum chemical : Quantum chemical : Quantum chemical data of Azdata of Azdata of Azdata of Azithromycinithromycinithromycinithromycin Compound CompoundCompoundCompound LUMO LUMO LUMO LUMO (eV) (eV)(eV)(eV) HOMO HOMO HOMO HOMO (eV) (eV)(eV)(eV) Δ ΔΔΔE E E E (Cal.Mol (Cal.Mol(Cal.Mol(Cal.Mol----1111)))) Dipole Dipole Dipole Dipole moment momentmomentmoment (Debye)(Debye)(Debye)(Debye) AzAzAzAzithromycinithromycinithromycinithromycin 25.968 23.989 1.979 3.2 ConcentConcentConcentConcentration of ration of ration of ration of Inhibitor ( Inhibitor (Inhibitor (Inhibitor (ppmppmppmppm)))) Charge Charge Charge Charge Transfer Transfer Transfer Transfer resistance (R resistance (Rresistance (Rresistance (Rcccctttt) ) ) ) Ohm.cm Ohm.cmOhm.cmOhm.cm2222 Double layer Double layer Double layer Double layer capacitance capacitance capacitance capacitance (C (C(C(Cdldldldl) ?F.cm) ?F.cm) ?F.cm) ?F.cm----2222 Inhibition Inhibition Inhibition Inhibition efficiency (%) efficiency (%)efficiency (%)efficiency (%) Blank 50 150 250 350 450 1.25 2.58 3.15 4.33 6.81 11.6 2.764x10 -4 1.064x10 -4 6.017x10 -5 2.884x10 -5 1.670x10 -5 7.460x10 -6 - 52 60 71 82 89