Characterization of anodic oxide layer on Ti-6Al-7Nb alloy obtained via electrochemical anodization process: microstructure, topography, and corrosion properties

Titanium and its alloys are currently among the most preferred materials for bone implants due to their excellent biocompatibility and mechanical properties. A major challenge, however, is surface structure design that enhances tissue integration. This study presents preliminary results on the surface modification of Ti-6Al-7Nb alloy using electrochemical anodization - anodic oxidation (AO) and micro-arc oxidation (MAO). The goal was to compare the morphology, composition, and corrosion behaviour of formed oxide layers using electron and X-ray sources methodologies and corrosion resistance, evaluated through potentiodynamic polarization and electrochemical impedance spectroscopy. Analyses indicated a self-organized nanotubular structure on anodized surfaces and a vermiform morphology on MAO-treated ones. The presence of amorphous TiO2 and Ti-α phases, with aluminium and niobium distributed in both oxide layers, has been also determined. Corrosion testing showed that both anodization processes improved the protective properties of the alloy. MAO coatings exhibited slightly higher polarization resistance compared to AO surfaces (superior corrosion protection). These results enhance understanding of how electrochemical surface treatments influence the microstructure and corrosion behaviour of titanium-based biomaterials. The findings are particularly relevant for the less-studied Ti-6Al-7Nb alloy and provide a foundation for optimizing surface engineering methods to improve implant performance.