A recently developed voltammetric technique using a strongly alkaline electrolyte (6 M KOH + 1 M LiOH) was successfully applied to clarify a corrosion mechanism of copper under atmospheric conditions. In contrast to conventional potentiometric methods with neutral or weak alkaline electrolytes (e.g., 0.1 M KCl), the developed method could give qualitative and quantitative information about the corrosion products of copper, including oxides (i.e., Cu2O and CuO) and hydroxide [Cu(OH)(2)]. In the presence of water under such atmospheric conditions, Cu(OH)(2) was the initial corrosion product formed on a copper surface. However, the surface Cu(OH)(2) layer did not grow much but dehydrated to become a layer of CuO. The thus-formed CuO layer grew until it became several molecules thick (similar to 2 nm). For further progress of corrosion, an inner Cu2O layer was generated by the proportionation reaction between the CuO layer and the base metal Cu. The inner Cu2O layer grew for the subsequent oxidation until the thickness reached a certain value (similar to 35 nm). For further oxidation, the top CuO layer grew again preferentially over the inner Cu2O layer. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3465636] All rights reserved.