Application of Pearson’s principle to interpretation of the duration of the residual protective effect of organic inhibitors as a function of the nature of a metal and anion

Abstract

Residual inhibition coefficients Kt of acidic corrosion by a mixture of an organic inhibitor and an anionic additive for Al, Zn, Fe, and Ni decrease linearly in time; the duration of the residual protective effect depends linearly on the logarithm of the anionic additive concentration in the preadsorption solution. The effect of anions on the values of Kt and τ for the studied mixtures is determined by the nature of the metal and anion. It is established on the basis of Pearson’s principle of hard and soft acids that the Kt and τ values grow upon an increase in the organic inhibitor concentration in preadsorption solutions, irrespective of the nature of the metal.