“…After PEO treatment, feature peaks of MgO (JCPDS #45-0946) and MgF 2 (JCPDS #41-1443) appeared, indicating the formation of crystallized MgO and MgF 2 in the PEO coating. As we all know, fluoride acid is always used to passivate the magnesium implants to enhance their corrosion resistance, forming an MgF 2 and MgO containing film [29][30][31]. However, the film formation rate was slow and the thickness of the film was restricted by decreased reaction interface of the dissolved magnesium as the reaction proceeding and the formed film did not produce long-term stable protection for the substrate, presenting many corrosion cracks on its surface.…”