Effects of anodizing biodegradable Mg-Zn-Zr alloy on the deposition of Ca-P coating

► Anodization was employed before deposition of Ca-P layer on the Mg-Zn-Zr alloy. ► The structure of hole in hole was formed on the Mg treated by two-step anodization. ► The optimum condition of two-step anodization is 8 mA/cm2 10 min + 16 mA/cm2 10 min. ► The interface of coating and anodized Mg is stronger than the one of direct deposition.