Effect of MAO/Ta2O5 composite coating on the corrosion behavior of Mg–Sr alloy and its in vitro biocompatibility

In this study, on the surface of Mg–Sr alloy, we prepared two layer coatings, Ta2O5 on the primary MAO (Micro-arc oxidation) coating, and finally obtain a MAO/Ta2O5 composite coating by a sol–gel method. The surface morphology, chemical composition and microstructure of coated and uncoated Mg–Sr alloy were characterized by SEM, EDS, XPS and XRD. The corrosion resistance of all samples was evaluated by electrochemical and hydrogen evolution tests. Its biocompatibility was tested by in vitro cell assay. It was found that the MAO/Ta2O5 composite coated Mg–Sr alloy presented good corrosion resistance, the corrosion current density of decreased from 2.3 × 10−5A/cm2 of MAO coating to 1.6 × 10−6A/cm2 of MAO/Ta2O5 composite coating in simulated body fluid because the micropores and microcracks in the MAO coating were perfectly sealed by the subsequent Ta2O5 layer. These results showed that MAO/Ta2O5 composite coating had better biocompatibility than the substrate and the MAO coating. This study might provide a coating strategy to improve the corrosion resistance and biocompatibility for the Mg–Sr alloy in biological restoration applications.