Corrosion behavior of additive manufactured CoCr parts polished with plasma electrolytic polishing

Abstract

This study investigated the corrosion behavior of the additive-manufactured CoCr parts to understand how the surface modification with plasma electrolytic polishing (PEP) influenced the corrosion resistance of CoCr alloy. As the open circuit potential (OCP) of the mechanical polishing (MP)-treated samples showed an anodic shift compared to that of the PEP-treated one and the oscillation in the OCP, this study inferred that the PEP process forms more corrosion-resistant oxide film based on the transmission electron microscope (TEM) and electrochemical impedance spectroscopy (EIS) results. After the PEP treatment, the continuous oxide film was observed on the polished sample's surface, which resulted in a stable OCP. Also, the EIS results showing the higher oxide resistance and charge transfer resistance, apparent two-time constants, and phase angle over 80 degrees indicated that the PEP-induced oxide film was more corrosion resistant, compared to the film formed by the MP process.