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, electro-chemical impedance spectroscopy (EIS) test and the immersion test were carried out in simulated body fluid (SBF) at 36.5 +/- 0.5 degrees C. The results showed that the thickness of Ti3O5-HA bio-ceramic coating increased by 2-11 mu m 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. (C) 2017 Elsevier B.V. All rights reserved.