THE ANODIC-DISSOLUTION OF COPPER IN HYDROCHLORIC-ACID SOLUTIONS

The electrodissolution of copper in hydrochloric acid solutions at the rotating ring-disk electrode was found to be controlled by both mass transfer and reaction in the apparent-Tafel region in HCl concentrations of between 0.1 and 1.0 M. The proposed mechanism describes the adsorption of CuClads on the corroding copper surface and the diffusion of CuCl; from the copper surface. The reaction in the limiting-current region was found to be controlled by the diffusion of Cl- to the copper surface through a porous CuCl layer that forms on the surface. The thickness of this porous layer is dependent on the stirring conditions, and independent of the Cl- concentration. Cu2+ is also produced at the Cu surface during electrodissolution. A mechanism describing the formation of a porous film of CuCl on the surface, the diffusion of Cl- through this film and the formation of Cu" has been proposed.