Electrochemical treatment of nickel-chromium alloy in deep eutectic solvents

This study investigates the effect of anodic potentiostatic treatment of a nickel-chromium alloy in deep eutectic solvents ethaline and reline (eutectic mixtures of choline chloride with ethylene glycol and urea, respectively) on surface morphology, chemical composition, microroughness, corrosion resistance, and electrocatalytic activity. The electrochemical treatment was performed at two arbitrarily selected potentials corresponding to the anodic dissolution of the nickel-chromium alloy in the specified deep eutectic solvents: 0.2 V and 1.0 V for ethaline, and 2.0 V and 2.7 V for reline (versus a silver reference electrode), at a temperature of 250C for 150 minutes. It was shown that anodic treatment promotes preferential dissolution of the chromium component of the alloy. As a result of the treatment, a reduction in surface defects and a decrease in the microroughness parameter Ra (from approximately 0.46 m to 0.25–0.35 m) were observed, indicating the occurrence of electrochemical polishing. It was found that anodic surface modification of nichrome in deep eutectic solvents leads to an increase in corrosion resistance and a decrease in electrocatalytic activity toward the hydrogen evolution reaction, the oxygen evolution reaction, and the urea oxidation reaction in an aqueous alkaline solution. Possible reasons for the observed effects are discussed.