Microstructure and corrosion resistance of Ti3O5-HA bio-ceramic coating fabricated on AZ80 magnesium alloy

The Ti3O5-HA bio-ceramic coating on the AZ80 magnesium alloy was fabricated in silicate electrolyte with fluorine potassium titanate (K2TiF6) and nano Hydroxyapatite (HA) by micro-arc oxidation (MAO). The K2TiF6 concentration in the electrolyte was adjusted to prepare coatings with different morphologies, composition and properties. Morphologies of the surface and cross-section were investigated by scanning electron microscopy (SEM). X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) were used to study the phase structure and chemical composition. The corrosion resistance was studied using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) test and the immersion test were carried out in simulated body fluid (SBF) at 36.5 ± 0.5 °C. The results showed that the thickness of Ti3O5-HA bio-ceramic coating increased by 2-11 μm compared with HA bio-ceramic coating, and the coatings consisted of MgO, MgF2, MgSiO4, Ti3O5 and HA. Besides, K2TiF6 concentration was a critical factor affecting the formation of Ti3O5-HA bio-ceramic coating, it had verified that the optimum K2TiF6 concentration was 10 g/L. The results after long time immersion test indicated that the Ti3O5-HA coatings improved the bioactivity and long-time protective ability in comparison with K2TiF6-free MAO coating.