Effect of potassium fluotitanate concentration on the corrosion resistance and degradation property of micro-arc oxidized ZM21 magnesium alloys

Magnesium (Mg) alloy is a focus biomaterial at present, while the rapid degradation rate in body fluid will hinder the practical clinical application. Therefore, surface modification of Mg alloy is essential. In the study, Mg–2Zn–Mn (ZM21) alloys and micro-arc oxidation (MAO) are used as the substrate and surface modification method. Then, the influence of potassium fluotitanate (K2TiF6) concentration in silicate basic electrolyte on the corrosion resistance and degradation of MAO coatings are studied. The results show that (1) TiF62− has obviously thickening effect, and adding 0.25 and 0.50 g/L K2TiF6 make the better corrosion resistance. (2) TiF62− concentration affects the coating quality, which is mainly attributed to F− generated by the reaction of TiF62− + 4OH− = TiO2 + 6F− + 2H2O. (3) Anatase TiO2 formed by ionization of TiF62− plays a role in sealing the micro-pores of MAO coating. (4) The hydrophilicity is improved, weight loss rate and pH value of MAO samples after immersion are obviously reduced, and available biological safety are improved, of which it is worth noting that the surface of K-0.75 sample has generated particles with a Ca/P ratio similar to hydroxyapatite (Ca10(PO4)6(OH)2, HA). (5) Cell adhesion test proves the available cytocompatibility.