Film Formation and Current Oscillations in the Electrodissolution of Cu in Acidic Chloride Media: I . Experimental Studies

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 1 M 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 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 film to account for oscillatory behavior is proposed.