Figure S1. The hemolysis test of samples: (a)the substrate; (b) the coating C1, C2, C3 from Effect of the second-step voltages on the structural and corrosion properties of silicon–calcium–phosphate (Si–CaP) coatings on Mg–Zn–Ca alloy

The applications of magnesium (Mg) alloys as biodegradable orthopedic implants are mainly restricted due to their rapid degradation rate in the physiological environment. In this study, Si–CaP MAO coatings were prepared on a Mg–Zn–Ca alloy by a second-step MAO process at different voltages in order to decrease the degradation rate and increase the bioactivity of the alloy. The microstructure and morphology of the samples were characterized using XRD, FT-IR SEM and EDS. The degradation behaviours of samples were evaluated using electrochemical techniques, and immersion test in simulated body fluid (SBF). The results indicate that the morphology of the Si–CaP coatings changed significantly with the Ca/P ratio the increasing of the second-step voltages. The Si–CaP containing coating produced at 450 V could significantly decrease the degradation rate of Mg and caused a slow increase of the pH of SBF solution. The haemolysis test concluded that the coating C3 did not cause haemolysis reaction. The corrosion resistance of Mg alloy was greatly improved with the Si–CaP coatings, and the Mg alloy with Si–CaP coating prepared at 450 V has the best corrosion resistance, which indicates that the Si–CaP coatings are promising for improving the biodegradation properties of Mg-based orthopedic implants. Haemolysis indicates that Si–CaP coating prepared at 450 V conform to the standard (YY/T0127.1-93).