EIS study of oxidation heat‐treatment effects on corrosion behavior of Ni10Cu11Fe6Al metallic inert anode inside molten calcium chloride salt

Abstract

In this research, the effects of oxidation heat‐treatment on the high‐temperature corrosion behavior of Ni10Cu11Fe6Al (wt%) alloy was investigated as a new inert anode in titanium electrolytic production. The alloys were prepared using vacuum induction melting (VIM) process and then exposed to the electrolysis in calcium chloride molten salt at 900 °C at −1.6 V versus graphite reference electrode for different immersion times. The cross‐section and surface of the alloys were characterized using scanning electron microscope (SEM), and their electrochemical behavior was investigated by electrochemical impedance spectroscopy (EIS). The results showed that the oxidized alloys have the greater number of porosities compared to those of the unoxidized alloys. Thus, the nickel‐based alloy became more sensitive to pitting resulting from oxidation. The corrosion penetration depth reached about 400 µm after 16 h of electrolysis for the oxidized alloys while being nearly 213 µm for the unoxidized alloys, which indicates the corrosion penetration depth increased by oxidation. Therefore, the oxidation during the electrolysis inside the molten salt offers better results for this alloy.