Electrochemical behavior and in situ observation of galvanic couples of copper and silver or zinc wires in acidic copper sulfate solutions

Abstract

The anodic dissolution reaction of copper in copper electro-refining was studied by considering the reaction of galvanic couples with different metals as impurities. In this study, zinc was chosen as a typical anodic impurity and silver as a cathodic impurity, and electrochemical measurements of galvanic couples with silver or zinc wires winding around a copper wire and in situ observation of the electrode surface using a stereo microscope were carried out. For comparison, copper wire with zinc or silver plating was used. As a result, even the simple method of winding silver or zinc wire around copper wire was able to capture the characteristic behavior of the galvanic reaction of silver and zinc on copper wire. It was also confirmed that zinc dissolution was accelerated by copper and copper dissolution was accelerated by silver, and that the effects were more promoted under anodic polarization. The crystallization and passivation of copper sulfate on the copper electrode surface and the dissolution behavior of silver were also observed. These results indicate that the experimental method presented in this study is an effective way to investigate the effects of impurities on the solubility and passivation of crude copper metal.