Passivation Characterization of Nickel-Based Glassy Alloys in Artificial Sea Water

The effect of different pH values of artificial sea water on the passivation behavior and the pitting corrosion resistance of Ni70Cr21Si0.5B0.5P8C <= 0.1Co <= 1Fe <= 1 (VZ1) and Ni72.65Cr7.3Si6.7B2.15C <= 0.06Fe8.2Mo3 (VZ2) glassy alloys were studied using impedance spectroscopy measurements (EIS), cyclic polarization, and electrochemical frequency modulation techniques. The results showed that the alloys undergo a general corrosion process and tend to form an oxide film on the alloy surface, developing a stable protective layer in the artificial seawater solution. In both alloys, the lower corrosion current density was observed at a pH of 8.5 but had less pitting corrosion resistance. The VZ1 alloy had a relatively lower passive current density value, having a smaller anodic hysteresis loop area compared to the VZ2 alloy. The effect of the medium's pH on corrosion potential, corrosion current density, pitting potential, and repassivation potential was investigated and discussed, as was surface morphology.