Electrodissolution Kinetics of Copper in Acidic Chloride Solutions

The anodic dissolution of copper in acidic chloride media was studied at a rotating disk electrode by the linear potential sweep method. The potential range from the rest potential to +400 mV vs. SCE, including a limiting current region, was investigated. Twenty different solutions of various chloride ion concentrations from 0.2 to 4M and various [K⁺] to [H⁺] ratios were tested. The observed anodic limiting current density was proportional to the square root of the rotation rate. A model, which assumes the formation of a film on the copper surface and diffusion of the chloride ions to the electrode as the rate‐determining step, has been developed to interpret the experimental data. Complexation constants, and are calculated as and, respectively, and . These results lead to the conclusion that in solutions with the complex, , is dominant, while at more concentrated chloride solutions, is the main complex formed. For , a considerable amount of the dissolved copper is in the form of Cu²⁺. This restricts the proposed mechanism for anodic dissolution of copper to solutions of higher chloride concentrations. The calculations do not preclude the validity of a previously proposed mechanism which suggests that diffusion of the cuprous chloride complex to the bulk of the solution is the rate‐determining step.