Anodic dissolution and passivation of gold, particularly in presence of chloride

Abstract

A study of the anodic behaviour of gold was performed on a rotating disc electrode by the potentiostatic method and cyclic voltammetry, in neutral and acidic sulphate solutions with and without addition of chloride. These measurements, combined with photopolarisation (performed on stationary electrode in K 2SO 4 solution) enabled an assumption of the general scheme of the mechanism of anodic processes on gold, involving: —in sulphate solutions: chemisorption of oxygen and OH −; building of the first layer by “place exchange” mechanism; further growth of the anodic layer by ionic migration; presence of semiconducting compounds on electrode surface. —in sulphate solutions with chloride: anodic dissolution of gold over a primarily formed layer on the electrode surface, diffusion-activation control of the dissolution process, and probable precipitation reaction with blocking of the electrode surface (at higher cd and insufficient chloride flux).