Formation of New Phases during Anodic Dissolution of Zn-Rich Cu-Zn Alloys

Preferential anodic dissolution of Zn from brass is examined from the point of view of the volume diffusion mechanism. Results from x‐ray investigations of partially dissolved γ‐brass (Cu 65 a/o (atomic per cent) Zn) and η‐brass [Cu 86 a/o Zn] specimens show the appearance of new, more Cu‐rich, intermediate and terminal phases. Gradients in chemical composition also result within individual phases and are always in the direction of copper enrichment. These results indicate that preferential anodic dissolution of Zn from Cu‐Zn alloy occurs to a significant extent via interdiffusion of the constituent metals in the alloy. Volume diffusion at 23 °C may be operative via excess mono‐ and divacancies, with divacancy diffusion prevailing at high total vacancy concentrations. A few data are presented on the preferential vaporization of Zn from Cu‐Zn alloy.