Electrochemical Study on Anodic Dissolution Mechanisms of Copper and Copper-Alloys in Fresh Water

Analyses of dissolution mechanisms of copper and copper-alloys are important to obtain the fundamental knowledge concerning corrosion and etching. Various electrochemical measurements were performed to investigate the electrochemical properties of copper and copper-alloys with a channel double flow electrode (CFDE). CFDE is one of hydrodynamic technique whose principle is similar to a rotating ring disk electrode. The mass transfer in the electrolyte solution can be controlled by the solution flow in the channel. Therefore, the measurement with CFDE allows direct information concerning dissolution rate and the species by monitoring the emitted ions from the working electrode at detecting electrode. For example, the in-situ detections of cuprous and cupric ions were carried out with measuring of polarization curves of copper, brass and bronze. The polarization curve of brass showed two potential regions for different dissolution mechanisms and the dezincing was serious in less noble potential region.

An electrochemical impedance spectroscopy (EIS) was used in order to discuss the detailed dissolution mechanisms because the EIS enables us to discriminate the time constants of elementary steps in the dissolution process. In addition, the formation of porous structure of brass surface due to dezincing was investigated with the equivalent circuit involving transmission line model (TLM).