Theory of competitive adsorption and its application to the anodic dissolution of nickel and other iron-group metals—I. Active dissolution in acid solution under steady state conditions

Abstract

Equations have been derived for the active anodic dissolution of nickel in acid solution under steady state conditions. They are based on the kinetics of two consecutive electron transfer reactions, combined with competitive adsorption of anion complexes with either adsorbed hydroxide complexes or adsorbed hydrogen. It has been shown that either mechanism is capable of explaining the observed pH dependence; the theory based on inhibition by adsorbed hydrogen has, however, distinct advantages. Arguments have been brought forward in favour of the direct participation of anions in the mechanism of dissolution. The agreement between the theory and the experimentally observed behaviour in solutions which contain either one or two types of anion is excellent. Application of the mechanism to the other iron-group metals Fe and Co has been considered.