Analysis of protective oxide films on copper—nickel alloys by photoelectron spectroscopy

Photoelectron spectroscopy was used to determine the elemental composition of thin films formed on 70:30 cupronickel exposed to sodium chloride solutions at different impressed electrochemical potentials. At anodic potentials below the passivation potential, ?0.350 V versus SCE under the experimental conditions, either no film or a film containing copper and nickel in the same ratio as the alloy existed on the alloy. At the passivation potential the spectrum of the passive film indicated primarily nickel oxide and was very similar to the spectrum obtained from a pure nickel specimen passivated in the same environment.