EFFECT OF ALKALINE SOLUTION CONCENTRATION ON THE PASSIVATION FILM OF Cu-Ni ALLOY

Passive films formed on a Cu-Ni alloy in various concentrations of alkaline environment were investigated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy and the Mott–Schottky approach. The wide passivation range of the copper-nickel alloy was tested in alkaline solutions of three concentrations. The oxide film on the specimen has a p-type semiconductor property, while the flat band potential (EFB) decreased with increasing solution concentration. The film resistance of the passive films increased with increasing solution concentration. The pAassive films showed a duplex structure, including an inner layer of oxide (Cu2O, NiO) and an outer layer of hydroxide (Cu(OH)2, Ni(OH)2).