Electrochemical behaviour of copper in neutral aerated chloride solution. II. Impedance investigation.

A.c. and EHD impedance measurements were performed on a Cu rotating disc electrode immersed in neutral aerated NaC1 and the results were compared with simulated curves according to the kinetic model developed in Part I. The agreement is good over the whole anodic range and at the corrosion potential. A slowing down of the mass transport rate is explained by diffusion through a surface layer (Cu20) at the corrosion potential and for the close anodic range. It is confirmed that, on the cathodic plateau, the interface may be considered as uniformly accessible for the cathodic partial reaction of oxygen reduction. However, at less cathodic potential a surface layer effect due to CuC1 must also be taken into account. Diffusion coefficients for both O2 and CuCI~- were determined by EHD impedance.