N.V.Lakshmi, P.A.Jeeva, S.Karthikeyan
Keywords: Corrosion inhibitor, Clotrimazole, hydrogen permeation
Abstract:
The influence of Clotrimazole (CMZ) on corrosion and hydrogen permeation through Stainless steel 304 in 2N H3PO4 and 2N HCl has been studied using weight loss measurements and various electrochemical techniques. The inhibitor is found to be more effective in retarding the metal corrosion in H3PO4 than in HCl. Potentiodynamic polarization studies clearly indicate that CMZ behaves as a mixed inhibitor. Hydrogen permeation studies and AC impedance measurements also proved an excellent performance of the compound in H3PO4. The adsorption of this compound on the mild steel surface obeys Temkin’s adsorption isotherm which is further validated by Quantum chemical calculations.
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ISSN 1466-8858 Volume 17, Preprint 2 3 submitted 10 11 January 2014 Corrosion and hydrogen permeation investigations of Stainless steel 304 in acidic solutions N.V.Lakshmi1, P.A.Jeeva2, S.Karthikeyan1* 1 Surface Engineering Research lab, CNBT, VIT University, Vellore - 632014, India 2Design Division, School of Mechanical and building Sciences, VIT University, Vellore -632014, India Abstract The influence of Clotrimazole (CMZ) on corrosion and hydrogen permeation through Stainless steel 304 in 2N H3PO4 and 2N HCl has been measurements studied using weight loss electrochemical techniques. The inhibitor and various is found to be more effective in retarding the metal corrosion in H3PO4 than in HCl. Potentiodynamic polarization studies clearly indicate that CMZ behaves as a mixed inhibitor. Hydrogen permeation studies and AC impedance measurements also proved an excellent performance of the compound in H3PO4. The adsorption of this compound on the mild steel surface obeys Temkin’s adsorption isotherm which is further validated by Quantum chemical calculations. Keywords: Corrosion inhibitor, Clotrimazole, hydrogen permeation 1* corresponding author (skarthikeyanphd@yahoo.co.in) 1. Introduction Antibiotics and allied drugs have been reported in recent years as corrosion inhibitors because of their less toxicity [1-3]. Organic compounds containing sulphur, nitrogen and oxygen atoms are capable of retarding metallic corrosion. While extensive investigations have been carried out on inhibitor properties of antifungal drugs , due attention has © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of 1 to the reviewers’ comments, be published online at Corrosion Science and Engineering. It will be reviewed and, subject http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 2 3 submitted 10 11 January 2014 not yet been paid to a systematic study on Clotrimazole as potential corrosion inhibitors for stainless steel alloys in high aggressive acidic media, i.e. 2N HCl and 2N H3PO4 . However, very few reports are available using clotrimazole as corrosion inhibitors for aluminium in HCl medium [4]. Most of the effective organic inhibitors have hetero atoms such as O, N, S containing multiple bonds in their molecules through which they can adsorb on the metal surface [5-8]. The corrosion inhibiting property of these compounds is attributed to their molecular structure. The lone pair of electrons on nitrogen imidazole ring of CMZ and delocalization of π electrons of three benzene rings of the present drug establishes the adsorption of the compound on SS 304 surface. All the above studies expose one common observation that Clotrimazole can be regarded as excellent corrosion inhibitors. But studies on the influence of Clotrimazole on hydrogen permeation through steel substrate during pickling are very scarce. It belongs to the class of imidazole and triazole derivatives for topical use and utilized in the treatment of fungal infection. A good inhibitor should have the following two important requisites: (1) it should have very good inhibition efficiency and (2) it should bring down the hydrogen permeation current to a considerable extent. Some organic compounds offer very high values of inhibition efficiency, but they have a insignificant effect in plummeting the hydrogen permeation current and vice versa. Compounds which come under this class produce hydrogen embrittlement in a later stage by the combination of permeated atomic hydrogen. This delayed failure creates cracking, pitting, breakage, etc., on the metal surface. 2. Experimental Stainless steel 304 specimens of compositions, C= 0.08%, Si = O%, Ni = 8%, Cr = 18% and Fe remainder, and of size 4 x 1 x 0.020 cm were used for weight loss and hydrogen permeation studies. A mild steel cylindrical © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of 2 to the reviewers’ comments, be published online at Corrosion Science and Engineering. It will be reviewed and, subject http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 2 3 submitted 10 11 January 2014 rod of the same composition as above and embedded in araldite resin with an exposed area of 0.283 cm2 was used for potentiodynamic polarization and AC impedance measurements. The inhibitor was preliminarily screened by a weight loss method described earlier. [9] Both cathodic and anodic polarisation curves were recorded potentiodynamically (1 mA s-1) using corrosion measurement system BAS Model: 1OOA computerised electrochemical analyzer (made in West Lafayette, Indiana) and PL-10 digital plotter (DMP-40 series, Houston Instruments Division). Platinum foils, Hg/Hg2Cl2/KCl (satd) were used as auxiliary and reference electrodes, respectively. The hydrogen permeation study was carried out using an adaptation of the modified Devanathan and Stachurski’s two compartment cell, as described earlier.[4] Double layer capacitance (Cdl) and charge transfer resistance values (R,) were obtained using AC impedance measurements as described in an earlier publication.” The surfaces of corroded and corrosion inhibited mild steel specimens were examined by diffuse reflectance studies in the region 200- 700 nm using U-3400 for different spectrometer (UV-VIS-NIR Spectrometer, Hitachi, Japan). 3. RESULTS AND DISCUSSION 3.1 Weight loss and Gasometric measurements Table 1 gives the values of inhibition efficiency concentrations of Clotrimazole for the corrosion of mild steel in 2N HCl and 2N H3PO4 obtained from weight loss and gasometric measurements. It is found that the compound inhibits the corrosion of mild steel in both acids, but more effectively in H3PO4. This can be attributed to the lesser adsorption of sulphate ions on the metal surface, thereby leaving more space for the organic molecules to get adsorbed. But in HCl the stronger © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of 3 to the reviewers’ comments, be published online at Corrosion Science and Engineering. It will be reviewed and, subject http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 2 3 submitted 10 11 January 2014 adsorption of the chloride ions on the metal surface leaves less space for organic molecules to get adsorbed. So in H3PO4, the coverage of the metal surface by the organic molecules is significantly more, giving rise to higher values of inhibition efficiency for all concentrations of the compound used [9]. The structure of the compound is given in Figure 1. N N C Cl Figure1. Structure of Clotrimazole. The inhibition of corrosion of brought about by Clotrimazole can be due to the following interactions: 1. The interaction between the lone pairs of electrons of the nitrogen atoms of the imidazole ring and the positively charged metal surface [10]. 2. The interactions between delocalized electrons of the benzene groups and the positively charged metal surface [11]. It is found that there is very good conformity between the values of inhibition efficiency obtained by weight loss and gasometric methods. © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of 4 to the reviewers’ comments, be published online at Corrosion Science and Engineering. It will be reviewed and, subject http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 2 3 submitted 10 11 January 2014 3.2 Potentiodynamic polarization studies Table 2(a) and 2(b) give values of corrosion kinetic parameters such as Tafel slopes ( ba and bc ),corrosion current (I corr ) and corrosion potential (E corr ) and inhibition efficiency obtained from potentiodynamic polarization curves for mild steel in 2NHCl and 2N H3PO4 containing different concentrations of inhibitor. It can be seen from this table that values of Tafel slopes and I 13]. Further it corr is are very much similar to those reported earlier [12ascertained that increasing concentrations of Clotrimazole enhances the values of both ba and bc in irregular fashion confirming that the inhibition of corrosion of SS 304 in both acids is under mixed control. Values of Ecorr are shifted to less negative values in the presence of different concentrations of CMZ. This can be ascribed to the formation of closely adherent adsorbed film on the metal surface. The presence of increasing concentrations of Clotrimazole retards I corr values in both the acids. It can also be seen that most of the values of inhibition efficiency obtained by weight loss measurements and potentiodynamic polarization studies agree very well. 3.3 Hydrogen permeation measurements Hydrogen permeation measurements results for the corrosion of mild steel in the presence and absence of the inhibitor are presented in Table 3.Hydrogen permeation current for mild steel in 2N HCl is more, because of the aggressive nature of chloride ions. It can be seen from the table that the presence of Clotrimazole in both acids decreases the permeation current and does not favor the ingress of hydrogen gas into SS 304. The reduction in permeation current can be attributed to the strong adsorption of the compound on the mild steel surface [12-15].It can be © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of 5 to the reviewers’ comments, be published online at Corrosion Science and Engineering. It will be reviewed and, subject http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 2 3 submitted 10 11 January 2014 seen from the table that the decrement of permeation current is more, if the concentration of Clotrimazole is more. 3.4 Impedance studies Values of charge transfer resistance (Rt )and double layer capacitance (Cdl) derived from Nyquist plots are shown in table 4.It can be found in table that the values of Rt is seen to increase with enhancement of CMZ concentrations in both the acids. Values of double layer capacitance are establishing that steel dissolution is more in 2N HCl than 2N H3PO4 .It is found that values of Cdl are lowered by increasing concentrations of antibiotic in both the acids. This can be ascribed to increased adsorption of the CMZ molecule on the metal surface with increase in its concentration. A plot of surface coverage (ø) versus log C presents a straight line illustrating that the adsorption of CMZ on SS 304 surface from both acids follows Temkin’s adsorption isotherm. This is major evidence to corrosion inhibition by this compound, as a consequence of its adsorption on the metal surface. © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of 6 to the reviewers’ comments, be published online at Corrosion Science and Engineering. It will be reviewed and, subject http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 2 3 submitted 10 11 January 2014 3.5 Quantum chemical studies: Fig 2.(a) Highly Occupied MO’s of inhibitors Fig.2(b)LUMO’s of inhibitors The computed quantum chemical indices such as energy of highest occupied molecular orbital (EHOMO), energy of lowest unoccupied molecular orbital (ELUMO), LUMO- HOMO, energy gap (∆E), dipole moment (), are summarized in Table 2. From figure 4, it can be observed that HOMO and LUMO energy orbital’s were strongly distributed on benzene groups and imidazole moiety for HOMO structure nitrogen and almost nil, on pyridine group in the case of LUMO establishing that the benzene moiety contains effective adsorption centres [17-19] and this is in agreement with publications of molecular orbital studies confronting that π electrons and N atoms are liable for inhibition activity [20]. According to karthikeyan et al. [21], when a molecule possesses similar frontier orbitals, its inhibition effectiveness can be allied to the energy levels of HOMO and LUMO and the distinction between them. It has been significantly claimed that, higher the value of EHOMO, larger is the ease for © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of 7 to the reviewers’ comments, be published online at Corrosion Science and Engineering. It will be reviewed and, subject http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 2 3 submitted 10 11 January 2014 an inhibitor to release electrons to unfilled d orbital of metal atom and higher is the inhibition performance. Also, lower ELUMO values, felicitate acceptance of electrons from metal atom to form feedback bonds. Hence the gap between HOMO–LUMO energy levels of molecules was considered as an important parameter. Smaller the value of ∆E of an inhibitor, greater is the inhibition efficiency of that compound. It has been reported that, large values of dipole moment will appreciably increase the corrosion inhibition [22-24]. 4. Conclusions 1. Clotrimazole inhibits the corrosion of SS 304 in both acids, but shows a better performance in 1N H3PO4. 2. The inhibition of corrosion of stainless steel in 2N HCl than 2N H3PO4, by the inhibitor is under mixed control. 3. The presence of inhibitor molecule in both the acids is found to reduce the extent of entry of hydrogen through steel surface. 4. R t and Cdl values studied from impedance measurements prove the improved performance of the compound. 5. The adsorption of the inhibitor on SS 304 surface follows Temkin’s adsorption isotherm. © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of 8 to the reviewers’ comments, be published online at Corrosion Science and Engineering. It will be reviewed and, subject http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 2 3 submitted 10 11 January 2014 Re fe re nce s : 1. Rhodanine azosulpha drugs as corrosion inhibitors for corrosion of 304 stainless steel in hydrochloric acid solution, M. Abdallah, Corros. Sci, 44, pp728, 2002 2. Antifungal drugs as corrosion inhibitors for aluminium in 0.1 M HCl, I.B. Obot, N.O. Obi-Egbedi, S.A. Umoren, Int. J. Electrochem. Sci, Vol. 4, 2009 3. 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 4. Adsorption characteristics and corrosion inhibitive properties of clotrimazole for Aluminium corrosion in hydrochloric acid, I. Obot, N.Umoren, Int. J. Electrochem. Sci, Vol. 4, pp. 863-877, 2009 5. 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 6. Influence of some thiazole derivatives on corrosion of mild steel in hydrochloric acid, M.A. Quraishi, M.A.W. Khan, M. Ajmal, Anti-Corros. Methods Mater, 43, 5, 1996 7. The inhibitive action of cyclohexyl thiourea on corrosion and hydrogen permeation through mild steel in acidic solutions, S. Karthikeyan, S.Harikumar, G. Venkatachalam, S.Narayanan, R. Venckatesh, International Journal of ChemTech Research, 4(3), pp. 1065-1071, 2012 8. Electrochemical studies of two corrosion inhibitors for iron in HCl, AlAndis, N.Khamis, E. Al-Mayouf, H. Aboul b Enicm, Corros. Prev. Cont rol, 42, 13,1995 © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of 9 to the reviewers’ comments, be published online at Corrosion Science and Engineering. It will be reviewed and, subject http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 2 3 submitted 10 11 January 2014 9. L-Methionine methyl ester hydrochloride as corrosion inhibitor of iron in 1 M HCl, B. Hamm outi, M. Aouniti, M. Taleb, M. Bri ghli, S. Kertit, Corrosion, 51,441, 1995 10. Influence of anions on corrosion inhibition and hydrogen permeation through mild steel in acidic solutions in the presence of p-tolyl thiourea, K. Madhavan, S. Karthikeyan, S.V.K. Iyer, Ind. J.Chem. Tech, 9, pp68, 2002 11. The Structure of the Electrical Double Layer at the Metal Solution Interface, M.A. Devanathan, B. Til ak, Chem.Revs, 65, pp. 635, 1965 12. Surface coordination chemistry of monometallic and bimetallic eletrocatalysts, Soriaga, Chem.Revs, 90, pp77, 1990 13. The inhibition of sulphuric acid corrosion of 410 stainless steel by thioureas, Reeta Agarwal, T.K.G. Namboodri, Corros.Sci, 30, pp37, 1990 14. Mechanism of corrosion and its inhibition, K. Madhavan, PhD Thesis, Alagappa Uni versity, India, June 1996 15. W.Waiter Voss, J.Chemistry of Amides, Zabersky Edition, Interscience, Newyork, 187, 1997 16. A.K. Lahiri, N.G. Banerjee, NML. Tech. Journal, 5, pp33, 1963 17. Gu Hough, Zhou Zhongbai, Tao Yingachu , Yao Luaw, Wahan Dauxe Xuebao, Ziran Kexuebaw, 2, pp57, 1982 18. G. Trabanelli and Zucchui F.Revon, Corrosion and coatings, 1, pp47, 1973 19. The use of Quantum chemical methods in corrosion inhibitor studies, G. Gece, Corrosion Science, pp.2981-2992, 2008 20. Inhibition Effect of Amoxicillin drug on the Corrosion of Mild Steel in 1N Hydrochloric acid Solution, S. Hari Kumar, S. Karthikeyan, S.Narayanan and K.N.Srinivasan, International Journal of ChemTech © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of 10to the reviewers’ comments, be published online at Corrosion Science and Engineering. It will be reviewed and, subject http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 2 3 submitted 10 11 January 2014 Research, 4(3), pp. 1077-1084, 2012 21. Corrosion inhibition of mild steel in 1M H2So 4 by Ampicillin as an inhibitor, S. Hari Kumar, S. Karthikeyan, P.A. Jeeva, Journal of Corrosion Science and Engineering, Vol16, 2013 22. The retardation of dissolution of Al-Sic composites in acidic medium – A green approach, V. Umasankar, S. Karthikeyan, M. Anthony Xavier, Journal of Corrosion Science and Engineering, 16, pp47, 2013 23. 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 24. Performance characteristics of 1, 3-diorthotolyl thiourea on the corrosion of mild steel in 5% NaCl, S. Karthikeyan, N. Arivazhagan, D. Ramkumar, S. Narayanan,, Journal of Corrosion Science &Engineering, Vol.16, 2013 © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of 11to the reviewers’ comments, be published online at Corrosion Science and Engineering. It will be reviewed and, subject http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 2 3 submitted 10 11 January 2014 Table 1. Values of inhibition efficiency for the corrosion of mild steel in 2N HCl and 2N H3PO4 in the presence of different concentrations of Clotrimazole obtained from weight loss and gasometric gasometric measurements. Concentration Inhibition efficiency (%) of Inhibitor (mM) HCl Weight loss Gasometric Studies 2 H 3P O4 79 Weight loss Gasometric measurements studies 794 85.2 measurements 85.8 4 83.2 83.5 94.1 94.6 12 91.0 91.2 95.4 95.5 36 94.4 94.7 98.2 98.7 © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of 12to the reviewers’ comments, be published online at Corrosion Science and Engineering. It will be reviewed and, subject http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 2 3 submitted 10 11 January 2014 Table 2.a Corrosion kinetic parameters of SS 304 in 2N HCl in the presence of different concentrations of Clotrimazole obtained from potentiodynamic polarization studies. Concentration Ecorr (mV) of Inhibitor Tafel slopes in mV in Inhibition dec-1 efficiency (mM) mA cm ba Blank Icorr -1 (%) bc 122 --- 2.89 -510 67 -487 74 120 0.53 79 4 -481 68 135 0.40 82.2 16 -472 72 0.26 91.2 32 -464 94 0.11 93.7 2 129 144 © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of 13to the reviewers’ comments, be published online at Corrosion Science and Engineering. It will be reviewed and, subject http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 2 3 submitted 10 11 January 2014 Table 2.b Corrosion kinetic parameters of SS 304 in 2N H2SO4 in the presence of different concentrations of Clotrimazole obtained from galavanostatic polarization studies. Concentration Ecorr (mV) of Inhibitor Tafel slopes in mV in efficiency mA cm ba 2 4 16 32 77 133 -884 72 141 -866 -861 -1 (%) bc -919 -873 Inhibition dec-1 (mM) Blank Icorr 2.45 --- 0.29 85.0 0.12 94.2 76 137 59 145 0.06 94.7 50 136 0.02 98.5 © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of 14to the reviewers’ comments, be published online at Corrosion Science and Engineering. It will be reviewed and, subject http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 2 3 submitted 10 11 January 2014 Table 3. 3. Values of permeation current for the corrosion of mild steel in 2N HCl and 2N H3PO4 in the presence of different concentrations of Clotrimazole. Clotrimazole. Concentration of Steady state permeation current (A) Inhibitor (mM) 1M HCl Blank 2 22.7 1M H3PO4 19.7 21.3 17.8 4 20.3 13.5 16 17.1 11.3 32 14.2 7.9 © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of 15to the reviewers’ comments, be published online at Corrosion Science and Engineering. It will be reviewed and, subject http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 2 3 submitted 10 11 January 2014 Table 4.Impedance parameters for the corrosion of Stainless steel 304 in 2N HCl and 2N H3PO4 in the presence of different concentrations of Clotrimazole. Concentration HCl H3PO4 of Inhibitor Charge Double layer Charge Double layer (mM) Transfer capacitance Transfer capacitance resistance (Cdl) F.cm-2 resistance (Cdl) F.cm-2 Blank (Rt) (Rt) Ohm.cm2 Ohm.cm2 235 6.9 185 32 168 34 167 4 40.3 131 48 125 16 73.1 118 82 108.3 32 92.0 101 127 78.4 2 5.3 Table 5: Quantum chemical parameters for Clotrimazole Compound Clotrimazole LUMO HOMO (eV) (eV) -1.891 -10.841 Dipole ∆E (Cal.Mol-1) moment (Debye) 8.95 5.4 © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of 16to the reviewers’ comments, be published online at Corrosion Science and Engineering. It will be reviewed and, subject http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work.