Effects of plasma electrolytic polishing treatment on the surface morphology, microstructure and corrosion resistance of additively manufactured TC4 titanium alloy

This study investigates the effect of plasma electrolytic polishing (PEP) on the surface morphology and corrosion resistance of TC4 titanium alloy parts fabricated by selective laser melting (SLM). Mechanical polishing (MP) was used as the control group. The surface topography, micromorphology, phase composition, open circuit potential (OCP), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) of both PEP- and MP-treated samples were compared and analyzed. The results demonstrate that the PEP process effectively eliminates the surface defects inherent to SLM, resulting in a smoother and more uniform surface compared to the MP-treated samples. Electrochemical analysis, including PDP and EIS, suggests that the oxide film formed after PEP treatment offers superior corrosion resistance. This enhancement is attributed to the higher β-phase content (18.4%) in the PEP-treated SLMed TC4 alloy, which contributes to the formation of a more stable oxide layer and increased charge transfer resistance. These findings expand the application of PEP technology and offer new solutions for enhancing the surface quality and corrosion resistance of additively manufactured TC4 titanium alloy.