P.A.Jeeva, S.Karthikeyan, Xianguo Hu
Keywords: Corrosion inhibitor, Thio compounds, Impedance measurements, Adsorption
Abstract:
The influence of Chloramphenicol (CPCL) on corrosion of mild steel in saline water
(5% NaCl) has been studied using weight loss, gasometric measurements, potentiodynamic polarization and impedance studies. The studies clearly indicated that CPCL acted as cathodic inhibitor. The adsorption of the compound on mild steel surface obeyed Temkin’s adsorption isotherm. Diffused reflectance spectra confirmed the formation of adsorbed film of inhibitor on metal.
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The influence of an environmentally friendly inhibitor on the corrosion of mild steel in saline water P.A.Jeeva1 , S.Karthikeyan 1*, Xianguo Hu2 1School of Mechanical Engineering, VIT University, Vellore- 632 014, India 2Institute of Tribology, Hefei University of Technology, Hefei, Anhui 230009, P.R. China 1* corresponding author (skarthikeyanphd@yahoo.co.in) Abstract The influence of Chloramphenicol (CPCL) on corrosion of mild steel in saline water (5% NaCl) has been studied using weight loss, gasometric measurements, potentiodynamic polarization and impedance studies. The studies clearly indicated that CPCL acted as cathodic inhibitor. The adsorption of the compound on mild steel surface obeyed Temkin’s adsorption isotherm. Diffused reflectance spectra confirmed the formation of adsorbed film of inhibitor on metal. Keywords : Corrosion inhibitor, Thio compounds, Impedance measurements, Adsorption Introduction Mild steel is an important category of materials due to their wide range of industrial applications. It is used in many industries due to its excellent mechanical properties. These are used in industries as pipelines for petroleum industries, storage tanks, shipment vessels and chemical batteries1 in seashore. Due to their high corrosive nature, salt water may cause damage to the steel components. Various methods are used to decrease the corrosion of steel in salt water. Among them, the use of inhibitors is most commonly suggested2-3. inhibitors4. Several substituted thioureas have been investigated as corrosion Most of the effective organic inhibitors have heteroatom such as O, N, S containing multiple bonds in their molecules through which they can adsorb on the metal surface5-8. The corrosion inhibiting property of these compounds is attributed to their molecular structure. The lone pair of electrons determines the adsorption of these molecules on the metal surface. The present paper describes a study of corrosion protection action of Chloramphenicol on corrosion of mild steel in saline water using weight loss, gasometric measurements and various electrochemical techniques. Chloramphenicol (CPCL) is an organic compound with π-electrons and heteroatom’s S, N & O. The molecule is big enough (Melting point :135) and sufficiently planar to block more 1 surface area due to adsorption on mild steel. These factors favour the interaction of CPCL with the metal. As far as we know no concrete report has been published so for CPCL in saline water with use of potentiodynamic polarization, impedance measurements and diffuse reflectance spectra. The structure of the CPCL is shown in the figure.1. Different concentrations of inhibitor were prepared and their inhibition efficiencies in 5% salt water were investigated. Experimental Mild steel specimens of compositions, C = 0.08%, P = 0.07%, Si = O%, S = O%, Mn = 0.41% and Fe remainder, and of size 4 x 1 x 0.020 cm were used for weight loss and gasometric studies. The weight loss study was carried out at room temperature for three hours in 5% NaCl. The inhibition efficiency (IE %) was determined by the following equation, I.E (%) = (W0 –Wi /W0) X 100 Where W0 & Wi are the weight loss values in the absence and presence of the inhibitor. A mild steel cylindrical rod of the same composition as above and embedded in araldite resin with an exposed area of 0.283 cm2 was used for potentiodynamic polarisation and AC impedance measurements. The inhibitor was preliminarily screened by a weight loss method described earlier9. Both cathodic and anodic polarisation curves were recorded in saline water (5% NaCl) potentiodynamically (1 mA s-1) using corrosion measurement system BAS Model: 100A computerised electrochemical analyzer (made in West Lafayette, Indiana) and PL-10 digital plotter (DMP-40 series, Houston Instruments Division). A platinum foil and Hg/Hg2Cl2/5%NaCl were used as auxiliary and reference electrodes respectively. Double layer capacitance (Cdl) and charge transfer resistance values (Rct,) were measured using AC impedance measurements 10-18. 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 spectrometer (UV-VIS-NIR Spectrometer, Hitachi, Japan). Results and Discussion Weight loss and Gasometric measurements Table 1 gives the values of inhibition efficiency for different concentrations of Chloramphenicol for the corrosion of mild steel in saline water obtained from weight loss and gasometric measurements. It is found that the compound inhibits the corrosion of mild steel effectively in salt water. The presence of propane-2-acetamide group in the molecule which shows inductive (+I) effect may increase the electron density on the nitrogen atom that leads to impressive performance of the compound. 2 A good conformity between the values of inhibition efficiency obtained by weight loss and gasometric methods is found. Potentiodynamic polarization studies The corrosion kinetic parameters such as Tafel slopes ( ba and bc ),corrosion current (Icorr ) and corrosion potential (Ecorr ) and inhibition efficiency obtained from potentiodynamic polarization curves for mild steel in saline water containing different concentrations of inhibitor are given in table 2. The values of ba, bc and Icorr are very much similar to those reported earlier 11-13. Further it is ascertained that increasing concentrations of CPCL enhances the values of both ba and bc ,but the values of bc are enhanced to greater extent. So the inhibition of corrosion of mild steel in salt water is under cathodic control. Values of Ecorr is shifted to less negative values in the presence of different concentrations of compound. This can be ascribed to the formation of closely adherent adsorbed film on the metal surface. The results of potentiodynamic polarization for the corrosion of mild steel in saline water are given in figure 2. Impedance measurements Corrosion inhibition of mild steel in saline water solution with and without inhibitor was investigated by electrochemical impedance spectroscopy measurements and it is shown in figure .3 and the results are presented in table 3. At all concentrations range of CPCL , large capacitive circle at higher frequency range followed by small capacitive loops at lower frequency range. The diameter of the circles increased with increase in inhibitor concentration. The higher frequency capacitive loop is due to the adsorption of inhibitor molecule14-18. Also the values of Rct are found to increase with increase in concentrations of compound in saline water solution whereas values of Cdl are reduced considerably . This can be ascribed to the strong adsorption of the compound on the metal surface. Similar observation was reported by Harikumar13 and others14-18 for the corrosion inhibition of mild steel in acidic media by Ampicilin drug and thio compounds. Diffused Reflectance Studies The formation of thin film on the surface of mild steel is ascertained by UV reflectance studies carried out using spectrophotometer in different concentrations of inhibitor with different mild steel specimens. The reflectance curves for polished specimen, specimen dipped in salt water and different concentrations of inhibitor are shown in the figure 4. The percentage of reflectance is maximum for polished mild steel and it gradually decreases for the specimen dipped in saline water solution. This observation reveals that the change in surface characteristic is due to the corrosion of mild steel in salt water. When compared 3 with uninhibited solution, the reflectance percentage increased as the concentration of the inhibitor increased .This can be ascribed to the increase in film thickness formed on mild steel surface 19. Conclusions 1. Chloramphenicol inhibits the corrosion of mild steel effectively in saline water. 2. The inhibition of corrosion of mild steel in salt water, by the compound is under cathodic control. 3. Rct and Cdl values obtained from impedance measurements confirm the better performance of the compound. 4. The adsorption of the compound on mild steel surface obeys Temkin’s adsorption isotherm. 5. UV –reflectance studies reveal the mere adsorption of the inhibitor on the mild steel surface accounted for the corrosion inhibition of steel in saline water. Re fe re nce s 1. Singh, I.. Inhibition of Steel Corrosion by Thiourea Derivatives (1993) Corrosion,, 49(6), pp. 473-478. 2. Agrawal,R., Namboodhri, T.K.G. Inhibition of sulphuric acid corrosion 316 stainless of 410 stainless steel by thioureas (1990) Corr. Sci, 30(1), pp. 37-52. 3. Sekine,I.A., Masuko,A., Senoo, K. Corrosion of AISI steel in formic acid and acetic acids (1987) Corrosion, 43 (9), pp. 553-560. 4. N.V.Lakshmi, S.Karthikeyan,N.Arivazhagan, The corrosion inhibition of Aluminium in 3.5% NaCl by isopropyl thiourea, International journal of ChemTech Research,2013, 5 (4), pp. 1959-1963. 5. S.Karthikeyan, P.A. Jeeva, Xianguo Hu, S. Harikumar and S. Narayanan, The influence of macro thiourea derivative on the corrosion of mild steel in marine environment , Oriental Journal of Chemistry ,2012, 28 (3) , pp. 1443-1448. 6. Murlidharan, S. Iyer, S.V.K. Influence of N-heterocyclics on corrosion inhibition and hydrogen permeation through mild steel in acidic solutions (1997) Anti-Corros. Methods Mater., 44, pp. 100-109. 7. Karthikeyan, S., Jeeva, P.A., Raja, K., Paramasivam, M., Studies on the reduction of mild steel corrosion and hydrogen permeation in acidic media, Journal of Corrosion Science and Engineering, 2015, 18. 8. Hammouti, B., Aouniti, M., Taleb, Brighli M., Kertit S. L-Methionine methyl ester hydrochloride as corrosion inhibitor of iron in 1M HCl (1995) Corrosion, 51,pp. 441-448. 4 9. Muralidharan, S., Madhavan, K., Karthikeyan, S., Iyer, S.V.K. Influence of anions on corrosion inhibition and hydrogen permeation through mild steel in acidic solutions in the presence of p-tolyl thiourea (2002) Ind. J.Chem. Tech., 9, pp. 68-77. 10. Devanathan, M.A., Tilak, B., The Structure of the Electrical Double Layer at the Metal-Solution Interface (1965) Chem. Revs, 65, pp. 635-643. 11. Karthikeyan, S., Jeeva, P.A., Narayanan, S., Inhibition performance of tobramycin on the dissolution of stainless steel 304 and ingress of hydrogen gas in acid medium, (2014), Journal of Corrosion Science and Engineering, 17. 12. Reeta Agarwal, Namboodri, T.K.G., The inhibition of sulphuric acid corrosion of 410 stainless steel by thioureas (1990) Corros.Sci, 30, pp. 37-52. 13. Karthikeyan, S., Jeeva, P.A., Paramasivam, M., The influence of sulfalene drug (SFL) on the corrosion and hydrogen permeation through stainless steel 304 in 5% NaCl-part I, (2014), Journal of Corrosion Science and Engineering, 17. 14. Hari Kumar,S and Karthikeyan,S, The influence of ampicillin on the corrosion inhibition of mild steel in 1n hydrochloric acid solution (2012) International Journal of Current Research and Review, 4, pp. 96-104. 15. Lakshmi, N.V., Jeeva, P.A., Karthikeyan, S., Corrosion and hydrogen corrosion permeation investigations of Stainless steel 304 in acidic solutions, (2014), Journal of Corrosion Science and Engineering, 17. 16. S.Karthikeyan, P.A.Jeeva, N.Arivazhagan,S.Narayanan, The inhibitive action of Tolyl-3,3 dimethyl thiourea on the corrosion of mild steel in brine water, Journal of Surface science &Technology 2013, Vol 28, No. 3-4, pp. 101-110, 2012. 17. Trabanelli,G., Zucchui F.Revon, Sulphur containing organic compounds as corrosion inhibitors (1973) Corrosion and coatings,1, pp. 47-54. 18. Karthikeyan, S., Jeeva, P.A., Narayanan, S., Inhibition performance of tobramycin on the dissolution of stainless steel 304 and ingress of hydrogen gas in acid medium, (2014), Journal of Corrosion Science and Engineering, 17 19. Hari Kumar,S and Karthikeyan,S, Inhibition of mild steel corrosion in hydrochloric acid solution by cloxacillin drug (2012) J. Mater. Environ. Sci. 3 (5) ,925-934. 5 Table 1. Values of inhibition efficiency for the corrosion of mild steel in saline water in the presence of different concentrations of Chloramphenicol obtained from weight loss and gasometric measurements. Concentration of Inhibitor (ppm) Inhibition efficiency (%) Weight loss Studies Gasometric measurements Blank --- --- 10 79 78.8 20 89 89 30 98 97.6 Table 2: Corrosion kinetic parameters of mild steel in saline water in the presence of different concentrations of CPCL obtained from potentiodynamic polarization studies. Con. Ecorr Icorr ba bc (A cm-2) (mV dec-1) (mV dec-1) IE θ CPCL (mV vs SCE) Blank -379.00 560 81.0 134.2 10 PPM -337.12 119.84 67.0 127.7 78.6 0.79 20 PPM -368.56 64.4 64.8 111.3 88.5 0.89 30 PPM -391.43 11.76 61.4 99.2 97.9 0.98 6 (%) - - Table 3.Impedance values for the corrosion of mild steel in saline water in the presence of different concentrations of Chloramphenicol.. Concentration of saline water solution Inhibitor Charge (ppm) Transfer Double resistance (Rct) Ohm.cm2 (Cdl) F.cm-2 Blank 41 165 10 93.8 35.47 20 127 18.81 30 142.6 3.3 OH OH Cl HN O Cl N O layer O Figure 1.Structure of Chloramphenicol 7 capacitance Figure 2. Potentiodynamic polarization plot for mild steel in saline water with different concentrations of inhibitor. Figure 3. Impedance curves for the corrosion of mild steel in saline water in the presence and absence of CPCL. 8 Figure 4. UV Reflectance curves for Mild Steel in salt water with different concentrations of inhibitor. Figure 5.Temkin’s adsorption isotherm for CPCL in saline water. 9