Comparison of electrochemical dissolution properties of Hastelloy X in NaCl and NaNO3 solutions

The electrochemical dissolution properties of Hastelloy X are of great significance to its electrochemical machining (ECM). This study focuses on the electrochemical dissolution properties of Hastelloy X in NaCl and NaNO3 solutions. The open circuit potential, polarization curve, electrochemical impedance spectroscopy (EIS) and current efficiency were investigated, and the dissolution mechanisms were revealed. The results revealed that the breakdown potential and electrochemical impedance in NaCl solution were smaller than that in NaNO3 solution, confirming that oxide film was broken more easily in NaCl solution. Local pits and many electrochemical products were observed on the surface, which were formed by electrochemical dissolution, and the main composition of products was the hydroxide and oxide. With the increase of current densities, the current efficiency increased in NaCl solution, while decreased in NaNO3 solution. The current efficiency values and surface roughness demonstrated that at high current density, the rate of electrochemical dissolution was higher in NaCl solution, but better surface quality can be obtained in NaNO3 solution. The research can provide valuable theoretical guidance for the ECM of aerospace parts related to Hastelloy X.