AN ELECTROCHEMICAL STUDY ON THE DISSOLUTION OF COPPER AND SILVER FROM SILVER-COPPER ALLOYS

The dissolution behavior of silver and copper from their elemental states and Ag/Cu alloys in ammoniacal solutions has been studied using rotating disk electrodes. The variables studied included concentration of ammonia, oxygen partial pressure, and rotating speed of the disk. The results have been interpreted in terms of the mixed potential theory. The effect of local current resistance on the overall current has also been examined as a part of the governing theory of the dissolution. The dissolution rate of copper from the alloys in terms of the same area of the Cu-phase has been found to be higher than that from pure copper due to the galvanic coupling, and it increased with the increase of the silver content in the alloy. When the surface area fraction is about 0.5, the galvanic current between the Ag- and Cu-phases is maximum. The dissolution of copper from its pure state and alloys is mainly oxygen diffusion controlled. Like pure silver, the dissolution of silver from its alloy is considered to be chemical reaction controlled.