Analytical Sciences

Highly Selective Determination of Copper Corrosion Products by Voltammetric Reduction in a Strongly Alkaline Electrolyte

Shigeyoshi NAKAYAMA,* Takenori NOTOYA,** and Toshiyuki OSAKAI***

*Analysis Technology Research Center, Sumitomo Electric Industries Ltd., 1-1-3 Shimaya, Konohana, Osaka 554-0024, Japan
**Japan Copper and Brass Association, 1-10-10 Ueno, Taitou, Tokyo 110-0005, Japan
***Department of Chemistry, Graduate School of Science, Kobe University, Nada, Kobe 657-8501, Japan

Until recently, there had been two conflicting views about the order of copper oxides (Cu₂O and CuO) in their cathodic reduction with a neutral or weak alkaline electrolyte (typically 0.1 M KCl). In 2001, we successfully employed a strongly alkaline electrolyte (SAE; i.e., 6 M KOH + 1 M LiOH) to achieve a perfect separation of the reduction peaks of the two oxides. It was then found that the oxides were reduced in SAE according to a thermodynamic order, i.e., “CuO → Cu₂O”, and also that the reduction of CuO occurred in one step. At an extremely slow scan rate of <0.2 mV s⁻¹, however, CuO appears to be reduced in two steps via Cu₂O. It has also been shown that the developed method with SAE can be applied to analysis of various corrosion products, including Cu₂S, Cu(OH)₂, and patinas. Use of the developed method has allowed researchers to clarify the mechanism of the atmospheric corrosion of copper.

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