BEHAVIOR OF COPPER ANODES CONTAINING OXYGEN, SILVER AND SELENIUM IMPURITIES DURING ELECTRO-REFINING

The anodic passivation of copper anodes containing oxygen, silver and/ or selenium as impurities has been investigated in sulphuric acid at 6 5.0+/-0.2 degrees C by voltammetric, chronopotentiometric acid impedan ce techniques. A stationary electrode was used at a slow potential sca n rate for the voltammetric technique. The voltammograms of the pure c opper and alloy copper anodes exhibit three characteristic regions: th e active dissolution, region I, the dissolution and precipitation, reg ion II, and a current plateau passivation, region III. Electrochemical results obtained in this study show that passivation of copper anodes increases when impurities are added in the following order: Cu --> Cu -O --> Cu-Ag --> Cu-Se --> Cu-Ag-Se. X-ray diffraction results show th at the anode surfaces, in the passive region, were covered by copper p owder, silver and selenides.