Electrochemical behaviour of copper–silver alloys in sodium carbonate aqueous solution

Abstract

The electrochemical behaviour of Cu–20 wt-%Ag and Cu–80 wt-%Ag alloys was studied in aerated Na₂ CO₃ solutions using cyclic voltammetry, potentiodynamic anodic polarisation, and current transient techniques. The microstructure of the compounds formed on the surface of the alloy during the anodic potential sweep was obtained using XRD analysis. The dissolution behaviour of either of the two constituents from the alloys resembles that of the pure state. The galvanic coupling effect enhances the dissolution of the less noble metal, copper, on alloying with silver. The anodic sweep potential exhibited seven anodic peaks A₁, A₂, A₃, A₄, A₅, A₆, and A₇ prior to the oxygen evolution reaction. These peaks are assigned to the formation of Cu₂O, Cu(OH)₂, CuO, Ag₂O, Ag₂ CO₃, and Ag₂O₂ respectively. Potentiostatic current/time transients showed that the formation of Cu₂O, CuO, Ag₂O, and Ag₂ CO₃ layers involves a nucleation and growth mechanism under diffusion control.