On The Electrochemical Behaviors of Copper-Gold Alloys

Abstract

The electrochemical behaviors of 75% Cu-Au, 50% Cu-Au and 25% Cu-Au alloys, having an ordered or disordered structure, and gold were studied in aqueous solutions of sodium chloride. The electrode reactions were investigated by: (1) The anodic and cathodic polarization curves measured by a semiconductor type potentiostat, (2) the calorimetric determination of copper and gold dissolved into electrolytic solutions during the anodic reaction, (3) the identification of anodic oxidation products on the alloy surfaces by measuring diffuse reflection spectra and by the electron diffraction method, and (4) the estimation of the topograph of specimens in a passive state.The selective dissolution of copper-gold alloys has been considered to progress with the selective dissolution of copper alone. In the present investigation, however, it may be concluded that the phenomenon proceeds not in the above process but with a complete dissolution of alloys followed by re-deposition of gold on the surface of specimens.The alloys having a superlattice structure were chemically more active than the disordered alloys of the same composition. It seems plausible that the chemical activity of the ordered alloys results from the occurrence of anti-phase domain boundaries, twin boundaries and dislocations during the order-disorder transformation.