Micro-Arc Oxidation of Ti-45Nb Alloy: Surface Characteristics and Corrosion Behavior for Potential Biomedical Application

New β titanium alloys such as Ti-45Nb have been investigated for biomedical applications due to their promising mechanical and biocompatible properties. However, studies on micro-arc oxidation applied to Ti-45Nb surfaces are still scarce. This study explores the effect of micro-arc oxidation treatments on Ti-45Nb alloy surfaces using two different acidic electrolytes for anodization. The resulting surfaces were characterized by scanning electron microscopy, X-ray diffraction, contact angle measurements, surface energy analysis, roughness parameters, open-circuit potential, potentiodynamic polarization, and electrochemical impedance spectroscopy. Anodization significantly increased surface roughness, especially with sulfuric acid affecting the Ra parameter and phosphoric acid influencing Rt. Wettability and surface energy improved noticeably with reduced dispersive and increased polar components. The combined acid treatment (H₃PO₄ + H₂SO₄) provided superior corrosion resistance, as demonstrated by more stable Open-Circuit Potential, lower corrosion current densities, and higher impedance values. Equivalent circuit modeling suggested a more protective and complex oxide layer, attributed to greater surface heterogeneity and oxide thickness. These results indicate that anodization with the mixed acid solution is the most effective method to enhance corrosion resistance and surface performance of Ti-45Nb alloys for biomedical implants.