The anodic oxidation of copper in 0.001 to 0.1M NaHCO3 and NaHCQ + NaC1 aqueous solutions at pH 8 has been studied using a rotating disk electrode. The first oxidation product is a thin porous Cu(I) oxide film formed by a solid-state mechanism. In the solutions containing low NaHCO3 concentrations (<0.05M), this film undergoes localized corrosion. However, for concentration of NaHCO3 > 0.05M, more positive anodic potentials, or longer exposure times, further oxidation of copper take place through the thin porous Cu(I) oxide film. This process results in the formation of a stable outer layer of the precipitated Cu(II) oxides and basic copper carbonate compounds which protect the electrode towards further corrosion. The presence of chloride ions in bicarbonate solution has a promoting effect on the breakdown of the passive film; they shift the corrosion and breakdown potentials towards more negative values. Bicarbonate has an inhibiting influence on the corrosion of copper, since it counters the aggressive attack of chloride ions.

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The formation, breakdown, and composition of the surface films formed on a copper rotating disk electrode at 25~ were studied by potentiodynamic and potentiostatic pulse measurements. The present results explain the nature of the pit initiation process, especially some characteristic values of pitting phenomena such as the critical breakdown potential and the induction time for pit nucleation on passive copper in contact with bicarbonate solution, pH = 8.3, containing aggressive sulfate ions. It was found that the critical breakdown potential, E~, and the inhibition potential, E1 depend on the concen-2 o 2 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.192.114.19 Downloaded on 2015-06-27 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.192.114.19 Downloaded on 2015-06-27 to IP