Biocompatible hybrid chitosan/hydroxyapatite coating applied on the AZ31 Mg alloy substrate: In-vitro corrosion, surface and structure studies

This study introduces an eco-friendly strategy for enhancing the anti-corrosion and in vitro anti-corrosion protection of the Mg alloy by chitosan-modified hydroxyapatite (HA) coating applied on the Mg AZ31 surface. The concentration of chitosan, immersion time and pH of post-treatment solution were studied. The coated and uncoated samples' corrosion behavior was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests. Also, the performance of samples was reviewed in simulated body fluid (SBF). X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX) and contact angle measurements were adopted for surface characterization. According to the electrochemical results, the best anti-corrosion performance with the highest polarization resistance is related to the HA-chitosan coating, which chitosan concentration, immersion time and pH of post-treatment solution are 0.1 wt%, 3 min and 8, respectively. Results indicated that the HA-chitosan 0.1 wt% coated AZ31 Mg alloy sample with dense morphology and lower corrosion current density leads to a lower Mg degradation in the SBF environment in comparison with other samples.