Hydrothermal fabrication of rGO/Apatite layers on AZ31 magnesium alloy for enhanced bonding strength and corrosion resistance

To enhance the Apatite layer/substrate bonding strength and improve the corrosion resistance, a reduced graphene oxide (rGO) reinforced apatite composite layers (rGO/Apatite layers) were fabricated on magnesium alloy by one-step hydrothermal treatment (HT). The results show that the rGO/Apatite layer and Apatite layer are both composed of CaHPO4 (DCP) and HA with a prismatic shaped grain, while the grain distribution of rGO/Apatite layer is more compact. The XPS test implies that the graphene oxide was incorporated into the layer successfully and transferred to reduced graphene oxide (rGO) during the hydrothermal process. The scratch test indicates that the rGO/Apatite layer presents a better bonding strength than the Apatite layer. Meanwhile, the rGO/Apatite layer enhances the corrosion potential of magnesium from -1.67 V to -1.33 V and the corrosion current decreases by one order magnitude, tested by potentiodynamic polarization test The immersion corrosion test indicates that both the hydrothermal layers show similar degradation behavior and corrosion rate. The results of the present study propose a feasible method to enhance the bonding strength of hydrothermal layers with a good corrosion resistance, which makes the apatite layer more practical in clinical application.