Effect of benzotriazole on surface processes during copper electrodissolution in sulfuric acid

Impedance spectra were obtained during anodic dissolution of Cu in 0.5M H sub 2 SO sub 4 and 40mM benzotriazole (BTA) at 25 deg C. The spectra were evaluated according to the hypothesis that the electrode is covered with a barrier film having a stoichiometric composition through which the current is transported by ionic conduction. This barrier film is itself covered with an outer porous film of corrosion products. The experimental impedance spectra were fit to the model with a nonlinear least squares program. A detailed analysis of the physical parameters obtained with this procedure suggested that the metallic ions transfer through the barrier film, which is likely to be hydrated copper sulfate or contains a non-negligible amount of BTA, under high-field conduction. Experiments carried out at the mass-transfer limiting current in the absence of BTA suggested that the electrode was also covered with a similar dual salt film, the inner layer of which, however, has a different chemical composition than in the presence of BTA. Graphs. 30 ref.--AA