The effect of addition of chloride ion on the corrosion of stainless steel 304 in Na2SO4 solution under constant ionic strength conditions at 30°C was studied using potential-time and potentiodynamic polarization techniques and it was found that the addition of chloride ion reduces the growth of protective passive film on the surface and increase corrosion current. The kinetics of dissolution in sodium chloride solution (0.05–0.5M) at 30°C was also studied and the kinetic rate equation was derived and was found to verify the following relationship: CCl？ where . 1. Introduction Stainless steels are corrosion-resistant iron-base alloys containing a maximum of % carbon and a minimum of 10.5% chromium by weight, this is the minimum amount of chromium that prevents the formation of rust in humid unpolluted atmospheres, hence the designation “stainless”. The high corrosion resistance of the stainless steel is attributable to the presence of thin and invisible passive film [1] characterized by stability, durability, adherence, and self-repairing. Austenitic stainless steels are an extraordinary family of stainless steel alloys that have exceptional corrosion resistance and equally impressive mechanical properties which allowed them to be used as a construction material in various aggressive environments such as heat exchanger systems, drilling platforms, wastewater treatment, and desalination plants. Factors contributing to their increased use are their long service life with low maintenance cost, ability to be recycled, and benign effect on the environment and human health. Although austenitic stainless steels show a very high corrosion resistance in many aggressive environments, they can suffer pitting corrosion in chloride environments [2]. The aggressiveness and ability of ions to initiate pitting are well known [3–5]. The most popular austenitic grades have been type 304 (containing 18% chromium, 8% nickel and also known by the UNS Number S30400). The pitting mechanism of passive 304 stainless steel (or 304 SS) in 3.5% NaCl [6] and in sulphuric acid media containing chloride ions [7] has been investigated. The aim of the present work is to study the kinetics of dissolution of 304 SS in sodium chloride solution (0.05–0.5？M) at 30°C. 2. Experimental Potential-time and potentiodynamic polarization measurements were achieved using frequency response analyzer Gill AC instrument. Polarization measurements were carried out at scan rate of 30？mV/min. The measurements were done in an electrochemical cell with three-electrode mode; platinum sheet electrode and
References
[1]
J. Sedriks, Corrosion of Stainless Steels, John Wiley & Sons, New York, NY, USA, 2nd edition, 1996.
[2]
A. Fossati, F. Borgioli, E. Galvanetto, and T. Bacci, “Corrosion resistance properties of glow-discharge nitrided AISI 316L austenitic stainless steel in NaCl solutions,” Corrosion Science, vol. 48, no. 6, pp. 1513–1527, 2006.
[3]
Q. Yang and J. L. Luo, “Effects of hydrogen and tensile stress on the breakdown of passive films on type 304 stainless steel,” Electrochimica Acta, vol. 46, pp. 851–859, 2001.
[4]
E. A. Abd El Meguid, N. A. Mahmoud, and S. S. Abd El Rehim, “Effect of some sulphur compounds on the pitting corrosion of type 304 stainless steel,” Materials Chemistry and Physics, vol. 63, no. 1, pp. 67–74, 2000.
[5]
S. S. El-Egamy and W. A. Badway, “Passivity and passivity breakdown of 304 stainless steel in alkaline sodium sulphate solutions,” Journal of Applied Electrochemistry, vol. 34, no. 11, pp. 1153–1158, 2004.
[6]
R. Wang and M. Kido, “Influence of input power to vibrator and vibrator-to-specimen distance of ultrasound on pitting corrosion of SUS304 stainless steel in 3.5% chloride sodium aqueous solution,” Corrosion Science, vol. 51, no. 8, pp. 1604–1610, 2009.
[7]
P. Q. Zhang, J. X. Wu, W. Q. Zhang, X. Y. Lu, and K. Wang, “A pitting mechanism for passive 304 stainless steel in sulphuric acid media containing chloride ions,” Corrosion Science, vol. 34, no. 8, pp. 1343–1349, 1993.
[8]
E. Blasco-Tamarit, D. M. Garcia-Garcia, and J. Garcia Anton, “Imposed potential measurements to evaluate the pitting corrosion resistance and the galvanic behaviour of a highly alloyed austenitic stainless steel and its weldment in a LiBr solution at temperatures up to 150 °C,” Corrosion Science, vol. 53, no. 2, pp. 784–795, 2011.
[9]
P. C. Pistorius and G. T. Burstein, “Growth of corrosion pits on stainless steel in chloride solution containing dilute sulphate,” Corrosion Science, vol. 33, pp. 1885–1897, 1992.
[10]
Yu. Zuo, H. Wang, J. Zhao, and J. Xiong, “The effects of some anions on metastable pitting of 316L stainless steel,” Corrosion Science, vol. 44, pp. 13–24, 2002.
[11]
A. M. Abdel-Gaber, B. A. Abd-El-Nabey, and M. Saadawy, “The role of acid anion on the inhibition of the acidic corrosion of steel by lupine extract,” Corrosion Science, vol. 51, no. 5, pp. 1038–1042, 2009.
[12]
A. M. Abdel-Gaber, B. A. Abd-El-Nabey, I. M. Sidahmed, A. M. El-Zayady, and M. Saadawy, “Inhibitive action of some plant extracts on the corrosion of steel in acidic media,” Corrosion Science, vol. 48, no. 9, pp. 2765–2779, 2006.
[13]
A. M. Abdel-Gaber, B. A. Abd-El Nabey, I. M. Sidahmed, A. M. El-Zayady, and M. Saadawy, “Effect of temperature on inhibitive action of damsissa extract on the corrosion of steel in acidic media,” Corrosion, vol. 62, no. 4, pp. 293–299, 2006.
[14]
A. Pardo, E. Otero, M. C. Merino, M. D. López, M. V. Utrilla, and F. Moreno, “Influence of pH and chloride concentration on the pitting and crevice corrosion behavior of high-alloy stainless steels,” Corrosion, vol. 56, no. 4, pp. 411–418, 2000.
[15]
J. R. Galvele, “Transport processes and the mechanism of pitting of metals,” Journal of the Electrochemical Society, vol. 123, no. 4, pp. 464–474, 1976.
[16]
A. M. Abdel-Gaber, B. A. Abd-El-Nabey, I. M. Sidahmed, A. M. El-Zayady, and M. Saadawy, “Kinetics and thermodynamics of aluminium dissolution in 1.0 M sulphuric acid containing chloride ions,” Materials Chemistry and Physics, vol. 98, no. 2-3, pp. 291–297, 2006.
[17]
G. Okamoto and T. Shibata, “Stability of passive stainless steel in relation to the potential of passivation treatment,” Corrosion Science, vol. 10, pp. 371–378, 1970.
