Study of dissolution mechanisms of copper in perchloric acid solution containing NaCl by channel flow double electrode and electrochemical quartz crystal microbalance

Active dissolution of Cu in perchloric acid solution containing NaCl is divided into three distinct potential regions, namely, a Tafel region, a limiting current region and an aggressive dissolution region. Cuprous and cupric ions dissolved from copper electrode were detected using a channel flow double electrode (CFDE) system. The dependence of the working electrode current and formation rates of cuprous and cupric ions on chloride concentration and electrolyte flow rate was determined. Dissolution mechanisms for three potential regions were proposed on the basis of the steady-state measurement. The proposed dissolution mechanisms were examined by an electrochemical impedance spectroscopy (EIS) and an electrochemical quartz crystal microbalance (EQCM). Dissolution efficiency of cuprous ions described a loop in the forth quadrant on the Nyquist plane suggesting the existence of adsorbed intermediate in the Tafel region. EQCM measurements indicated that the final products in the Tafel region were cuprous ions. Copyright (C) 1996 Elsevier Science Ltd.