Effect of Nickel Content on the Corrosion and Passivation of Copper-Nickel Alloys in Sodium Sulfate Solutions Available to Purchase

The effect of Ni content on the corrosion and passivation behaviors of copper-nickel alloys with different Cu to Ni ratios was investigated in neutral sulfate solutions. The influence of working conditions (e.g., immersion time, sulfate ions concentration, and temperature) on the electrochemical behavior of the different alloys was also studied. In this respect, conventional electrochemical methods like open-circuit potential (OCP) measurements, polarization techniques, and electrochemical impedance spectroscopy (EIS) were used. It was found that the initial corrosion resistance is relatively low for alloys with high nickel content. An increase in the nickel content and long immersion time in the neutral sulfate solution increases the corrosion resistance of the alloy and improves its stability. The stability of the alloy was considered to be due to the formation of a stable passive film on its surface. The impedance data were fitted to theoretical data obtained according to an equivalent circuit model describing the electrode/electrolyte interface. The mechanism of the alloy passivation was discussed in view of the obtained results.