The influence of the copper/nickel ratio on the electrochemical behavior of Cu-Ni alloys in acidic sulfate solutions

The electrochemical behavior of Cu-Ni alloys with different Ni contents (5-65 mass%) in acidic sulfate solutions was investigated. The effects of working conditions e.g. concentration of sulfate ions, immersion time and temperature were studied and discussed. In this respect, open-circuit potential measurements, polarization techniques and electrochemical impedance spectroscopy (EIS) were used. Potentiodynamic measurements revealed that the increase in the Ni content improves the stability of the Cu-Ni alloys. The polarization measurements were confirmed by EIS experiments. The stability of the alloys with higher Ni contents is due to the increased amount of Ni in the surface film. The corrosion process of the cupronickels in the acidic sulfate solution was found to be diffusion controlled. The experimental impedance data were fitted to theoretical data according to an equivalent circuit model representing the electrode/electrolyte interface.