Electrochemical behaviour of copper-nickel alloy in chloride solution

Cyclic voltammetric measurements were made on pure copper, nickel and 70/30 copper-nickel alloy in sodium sulphate and sodium chloride (0.5 M) solutio ns. In sodium sulphate solution the passivation of copper and nickel is thr ough oxide formation. The passive film on copper nickel alloy is found to h ave nickel ions ingress along with copper oxide by volume diffusion. Nickel ions cause hindrance to the reduction of copper oxide to copper. The prese nce of chloride ions increases the dissolution of nickel while copper is pa ssivated. The formation of CuCl2 and its subsequent hydrolysis to hydroxide prevents the dissolution. Introduction of nickel in copper depassivates th e copper and hydrolysis of monovalent copper complex is prevented by the in gress of nickel ions. The formation of NiCl2 along with CuCl2 is facilitate d by chloride ions.