S.Karthikeyan, R.Dinakaran
Keywords: Corrosion, potential, impedance, inhibition
Abstract:
The reduction of dissolution of Zinc sheet could be achieved by using SULFASALAZINE as inhibitor in 2M KCl. The computational quantum mechanical analysis for inhibition performance of the compound has been studied using values of EHOMO, ELUMO, ΔE and dipole moment, mass loss, gasometric and electrochemical studies. Potential-Current Curves manifested that the inhibitor follows mixed type of inhibition in industry environment. The adsorption of inhibitor on Zinc sheetsurface obeyed Temkin’s adsorption isotherm.
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An investigation on the corrosion Zinc sheet in battery electrolytes S.Karthikeyan*, R.Dinakaran Centre for Innovative Manufacturing Research, VIT University, Vellore -632014, India School of Mechanical Engineering, VIT University, Vellore -632014, India *Corresponding Author (skarthikeyanphd@yahoo.co.in) Abstract The reduction of dissolution of Zinc sheet could be achieved by using SULFASALAZINE as inhibitor in 2M KCl. The computational quantum mechanical analysis for inhibition performance of the compound has been studied using values of EHOMO, ELUMO, ∆E and dipole moment, mass loss, gasometric and electrochemical studies. Potential-Current Curves manifested that the inhibitor follows mixed type of inhibition in industry environment. The adsorption of inhibitor on Zinc sheetsurface obeyed Temkin’s adsorption isotherm. Keywords: eywords: Corrosion, potential, impedance, inhibition 1. Introduction Zinc sheet is an important category of metals due to its excellent mechanical properties. It is widely used under different conditions in chemical and allied industries in handling acidic, alkaline and salt solutions. Zinc is used in automobile and battery industries as bus bars, anodes, sacrificial anodes for petroleum industries, reaction 1 vessel and neutral chemical containers [1]. When Zinc sheet is exposed to an industry environment containing chloride ions that causes damage to the substrate, because of their corrosive nature. Several methods were used to decrease the corrosion of Zinc metals in acidic medium, but the use of inhibitors is most commonly used [6-10]. Organic compounds are widely used as corrosion inhibitors for steel in acidic media [11-16]. The rate of corrosion decreases by adsorption of organic inhibitors on the metal surface. The inhibitors block the active sites by displacing water molecules and form a compact barrier film on the metal surface. The most of the organic inhibitors are toxic, highly expensive and non environment friendly. Research activities in recent times are geared towards developing the cheap, non-toxic drugs as environment friendly corrosion inhibitors [17-18]. The aim of this work is to investigate the corrosion protection efficiency of Sulfasalazine (SULFASALAZINE). For stainless steel corrosion in 2M KCl. The molecular weight of the compound is 312.4.The authors came to know that no concrete report is available for the use these compounds as corrosion inhibitors in 2M KCl. From the literature the higher concentration of Na2SO4 acts as descaling chemical for stainless steel used as cathodes for anodizing, battery electrodes in the presence of sulphur containing organic compounds. Use of this inhibitor in 2M KCl will reduce the metal loss in acid medium. The compound is large enough and sufficiently planar to block more surface area on the Zinc surface. The inhibition efficiency was calculated using weight loss measurement, potentiodynamic polarization studies, impedance techniques, and quantum mechanical methods. A definite correlation exists 2 between different types of descriptors and measured corrosion inhibition efficiency for Sulfasalazine using chemical and electrochemical techniques. 2. Experimental Zinc sheet specimens of the following composition was widely used. C= 0.02%, Si = 0.25%, Ni = 1%, Cr = O% and Zn= balance with exposed area of 4 x 1 x 0.020 cm were used for weight loss and gasometry measurements. A stainless steel cylindrical rod of the same composition as above and embedded in araldite resin with an exposed area of 0.3 cm2 was used for potential-current plots and EIS measurements. The compound Madhavan et al [9]. was mainly monitored by a weight loss studies as reported by Cathodic and anodic potential- current curves were recorded galvano statically (1 mA s-1) using corrosion measurement system BAS Model: 1OOA computerised electrochemical analyser (made in West Lafayette, Indiana) and PL-10 digital plotter (DMP-40 series, Houston Instruments Division). A platinum foil of 4 cm2, Hg/Hg2Cl2/KCl (satd) was used as auxiliary and reference electrodes, respectively. Double layer capacitance (Cdl) and charge transfer resistance values (R,) were obtained using EIS measurements. A special computational program has been used to interpret theoretical values of EHOMO, ELUMO, ∆E and dipole moment of SULFASALAZINE in 2M KCl 3 3. RESULTS AND DISCUSSION 3.1 Weight loss and Gasometric measurements Table 1 indicates of SULFASALAZINE the results of inhibition efficiency for various concentrations for the corrosion of Zinc sheet in 2M KCl determined from weight loss and gasometric measurements. It is perceived that the inhibitor checks the dissolution of stainless steel in 2M KCl. Also, the coverage of the Zinc sheet by the inhibitor is extensively more, giving rise to greater values of inhibition effect for all concentrations of the inhibitor used. The structure of the compound is given in Figure 1. N HN O S O HN N O HO O Figure 1.Structure of Sulfasalazine 4 The retardation on the dissolution of Zinc sheet in acid medium favoured by SULFASALAZINE were involving the following interactions: 1. The interaction between the lone pairs of electrons of the Sulphur and nitrogen atoms of the thiouurea group of of SULFASALAZINE and the positively charged metal surface [10]. 2. The interactions between delocalized electrons of the nitrogen atoms in the quino lino moiety and the positively charged metal surface of the green inhibitor [11]. It is found that there is a very good agreement between the values of inhibition efficiency obtained by mass loss and gasometric studies. 3.2 Potential alPotential -Current plots Table 2(a) and 2(b) gave the results of potential-current curves such as Tafel slopes ( ba and bc ),corrosion current (I corr ) and corrosion potential (E corr ) and inhibition efficiency obtained from galvanostatic polarization studies for Zinc sheet in 2M KCl containing several concentrations of SULFASALAZINE. It can be envisioned from this table that outcomes of Tafel slopes and I previously [12, 13.] Further it is corr are very much similar to those reported proven 5 that increasing concentrations of SULFASALAZINE increases the values of ba and bc in irregular fashion alleviating that the inhibition of corrosion of Zinc sheet in 2M KCl follows mixed type. Values of Ecorr is shifted to positive direction in the presence of different concentrations of inhibitor. This can be accredited to the establishment of firmly adsorbed inhibitor layer on the steel surface. The presence of increasing quantity of inhibitor molecule ominously impedes I corr values in the acids. It can also be found that most of the values of inhibition efficiency obtained by weight loss and potential-curve studies agree very well. 3.3 3. 3 Impedance studies The results of charge transfer resistance (Rt) and double layer capacitance (Cdl) acquired from EIS measurements are shown in table 4. It can be noticed from the table that the values of Rt is perceived to increase with enhancement of SULFASALAZINE concentrations in 2M KCl. It is observed that values of Cdl are lowered by increasing concentrations of SULFASALAZINE in 2M KCl. This can be attributed to the strong adsorption of the thiourea compound on the surface of Zinc sheet with increase in its amount to the electrolyte containing sulphate ions. 6 A plot of surface coverage (ø) versus log C gave a straight line signifying that the adsorption of SULFASALAZINE on Zinc sheet surface in in 2M KCl observes Temkin’s adsorption isotherm [16]. This is main evidence to corrosion inhibition by this compound, as a result of its adsorption on the surface of SS 304. 3.4 3. 4 Quantum chemical studies: Fig.2 Fig.2 Highly Occupied MO’s of SULFASALAZINE Fig.3 Lowest unoccupied MO’s of SULFASALAZINE The computed quantum chemical indices such as energy of highest occupied molecular orbital (EHOMO), energy of lowest unoccupied molecular orbital (ELUMO), LUMOHOMO, energy gap (∆E), dipole moment (), are summarized in Table 2. From figure 2 and 3, it can be observed that HOMO and LUMO energy orbital’s were strongly 7 distributed on amino groups and and pyran-diol for HOMO and LUMO structures establishing that the Sulfasalazine (SULFASALAZINE) posses good adsorption centers [19–20] and this is in agreement with publications of molecular orbital studies confronting that π electrons and N atoms are liable for inhibition activity. According to Hari Kumar et al [21], when a molecule has similar distribution of electronic orbital’s, its inhibition performance could be associated with the energy values of HOMO and LUMO and the difference in values between them. It has been widely stated that, higher the value of EHOMO, larger is the easiness for an inhibitor to release electrons to vacant d orbital of Iron atom and higher is its adsorption. Also, lower ELUMO values, favour obtaining capacity of electrons by the inhibitor from Fe atom to form feedback bonds. Hence the gap between HOMO–LUMO energy levels of molecules was dignified as an vital data. Smaller the value of ∆E of an inhibitor, greater is the inhibition efficiency of that compound. It is further claimed that, large values of dipole moment will noticeably elevate the adsorption of the compound on stainless surface [22-24]. 4. Conclusions 1. SULFASALAZINE retards the dissolution of the corrosion of SSZinc sheetin 2M NaCl. 2. The inhibition of corrosion of Zinc sheet by the compound falls under mixed Type. 3. Rt and Cdl values studied from impedance measurements prove the impressive performance of the inhibitor. 8 4. The adsorption of the compound on Zinc sheet surface follows Temkin’s adsorption isotherm. References: 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 Cefradine for Aluminium corrosion in hydrochloric acid, I. Obot, N.Umoren, Int. J. Electrochem. 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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. 12 Table 1. Values of inhibition efficiency for the corrosion of mild steel in 5M Na2SO4 in the presence of different concentrations of SULFASALAZINE obtained from weight loss and gasometric measurements. Concentration Inhibition Efficiency of Inhibitor Weight loss Gasometric (mM) Studies measurements 10 43 42.4 50 53 53 100 87 86.7 150 99 98.6 13 Table 2. Corrosion kinetic parameters of Zinc sheet in 2M different concentrations of SULFASALAZINE KCl in the presence of obtained from galvanostaic polarization studies. Concentration Ecorr (mV) Tafel slopes in mV in of Inhibitor dec-1 Icorr Inhibition efficiency (mM) A cm-2 ba (%) bc Blank -810 187 151 10 -798 165 142 590 -- 337.48 42.8 50 -775 172 145 279.66 52.6 100 -710 148 132 79.06 86.6 150 -709 156 147 5.9 99 14 Table 3.Impedance parameters for the corrosion of Zinc sheet in 2M KCl in the presence of different concentrations of Sulfasalazine . Concentration 2M KCl of Inhibitor Charge Double layer (mM) Transfer capacitance resistance (Cdl) F.cm-2 (Rt) Ohm.cm2 Blank 10 50 100 150 24 37 49 133.2 266.4 15 243 138.51 114.93 32.07 2.91 Table 4: Quantum chemical parameters for SULFASALAZINE Compound SULFASALAZINE LUMO HOMO (eV) (eV) -5.3585 -7.7855 Dipole ∆E (Cal.Mol-1) moment (Debye) 2.427 16 3.883