Influence of Chloride Concentration on the Active Dissolution and Passivation of Nickel Electrodes in Acid Sulfate Solutions

Abstract

The influence of Cl− ion concentration on the active dissolution and passivation of polycrystalline nickel rotating disk electrodes in sulfuric acid‐potassium sulfate solutions at pH 2.6 and 25°C was studied. The voltammetric data suggest that the passive layer results from a complex reaction involving the electrodissolution of the base metal, the formation of the anodic layer and its partial chemical dissolution. The influence of Cl− ions under different hydrodynamic conditions is discussed taking into account the competitive adsorption involving Cl− ions and species containing oxygen at the initial stages of the reaction yielding soluble products, and the appearance of as a new phase. Solution stirring favors the electrodissolution reaction by increasing the transport rate of Cl− and H+ ions to the electrode surface, and simultaneously decreasing the thickness of the layer.