Corrosion and inhibition of stainless steel pitting corrosion in alkaline medium and the effect of Cl- and Br- anions

The effect of carbonate anion on the pitting corrosion and inhibition behavior of stainless steel samples (304L SS and 316L SS) has been studied using potentiodynamic and scanning electron microscope (SEM) techniques. The effect of concentration of CO32- ions, pH, potential scanning rate and the composition of stainless steel are discussed. Additions of Cl- and Br- ions into the carbonate solution increase the anodic dissolution of stainless steel and decrease its pitting corrosion resistance. The effect of CO32- anion on the inhibition of chloride and bromide pitting corrosion of the two stainless steel types has been studied also. Pitting corrosion decrease with the increasing of sodium carbonate concentration, i.e. increases the resistance of stainless steels towards the chloride and bromide pitting corrosion. This inhibition effect argued to formation of [Fe,Cr]CO3 film caused by preferential adsorption of the CO32- ion, leading to instantaneous repair of weak sites for pit nucleation. (C) 2004 Elsevier B.V. All rights reserved.