New approach for improving anticorrosion and biocompatibility of magnesium alloys via polydopamine intermediate layer-induced hydroxyapatite coating

•A new method to prepare hydroxyapatite coating induced by polydopamine inner layer has been reported.•The polydopamine inner layer promotes the growth of hydroxyapatite coating via hydrothermal treatment.•Polydopamine-induced hydroxyapatite coating shows dense structure and good corrosion resistance. Although magnesium alloys have become a promising candidate for bone implant materials, their rapid degradation has limited their use in medical applications. Surface modification is a feasible strategy for solving the corrosion problem of magnesium alloys. Here, we report a novel hydroxyapatite coating induced by polydopamine obtained using the hydrothermal treatment. The surface morphology and composition of the coating were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. It was found that the dopamine-induced hydroxyapatite coating exhibits a more compact structure than the pure hydroxyapatite coating. Potentiodynamic polarization and simulated body fluid immersion tests demonstrated that the polydopamine-induced hydroxyapatite coating significantly reduced the corrosion rate due to the synergistic effect of the inner polydopamine layer and the outer hydroxyapatite coating. The cytocompatibility tests indicated that the composite coating significantly promoted the proliferation, adhesion and spread of osteoblasts. Thus, this coating may be a promising new approach for the surface modification of magnesium alloys.