%0 Journal Article
%T Kinetics of Pitting Dissolution of Austenitic Stainless Steel 304 in Sodium Chloride Solution
%A M. Saadawy
%J ISRN Corrosion
%D 2012
%R 10.5402/2012/916367
%X The effect of addition of chloride ion on the corrosion of stainless steel 304 in Na2SO4 solution under constant ionic strength conditions at 30¡ãC 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¨C0.5M) at 30¡ãC 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¨C5]. 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¨C0.5£¿M) at 30¡ãC. 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
%U http://www.hindawi.com/journals/isrn.corrosion/2012/916367/