Analytical Sciences

Abstract − Analytical Sciences, 28(4), 323 (2012).

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.