Ring‐disk electrode studies of anodic polarization of Cu in acidic chloride solutions indicate four distinct potential regions: the apparent Tafel region, the peak current and current minimum region, the limiting current region, and potentials above the limiting current region. Ring currents measured the flux of cuprous and cupric species from the disk. Dependence of disk and ring currents on H+ and Cl− and on rotating rate has been determined. Models are proposed to describe Cu electrodissolution in the apparent Tafel region and the potential region above the limiting currents. The results indicate mixed mass‐transfer and kinetic control with cuprous chloride complex as the limiting diffusion species in the apparent Tafel region. At potentials above the limiting current region, there is simultaneous mass‐transfer control of the cuprous chloride complex and kinetic control of Cu++ formation via the reaction, CuCl2−=Cu+++2Cl−+e . Within the peak current and current minimum region and the limiting current region, Cu electrodissolution by mass transport is controlled in accord with previous work.

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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 CuCI 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, K2 and K3 are calculated as 6.67 • 104 and 1.81 • 10~, respectively, and K3/K2 ~ 2.67. These results lead to the conclusion that in solutions with [CI-] ( 0.7M the complex, CuCI2-, is dominant, while at more concentrated chloride solutions, CuCla 2-is the main complex formed. For [C1-] ( 0.05M, a considerable amount of the dissolved copper is in the form of Cu 2+. 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.The anodic dissolution of copper in chloride solutions is still not completely understood even though there have been a number of investigations of this * Electrochemical Society Active Member.

Oscillatory behavior of Cu electrodissolution in various acidic chloride solutions was studied with rotating disk electrodes. Oscillations were not observed in the apparent Tafel region. However, for 0.5 and 1M Cl−, nonsustained oscillations were found in the peak‐current, current‐minimum, and current‐plateau regions. At potentials above the current‐plateau region, apparent sustained oscillations were observed. Oscillatory behavior disappeared at sufficiently high rotation rates. Film dissolution studies indicate that the normalCuCl film begins to form at potentials near the peak current and suggest that oscillations only occur with the formation of a sufficiently thick film. A model based on the diffusion of chloride ions through the porous normalCuCl film to account for oscillatory behavior is proposed.