Multifunctional coating of AZ31 Mg alloy using Azadirachta indica and PVA for enhanced biocompatibility

Abstract

Abstract Magnesium (Mg) alloys are promising candidates for biodegradable orthopedic implants due to their mechanical compatibility and biocompatibility; however, rapid corrosion and hydrogen gas evolution in physiological environments limit their clinical application. This study presents a green, biocompatible coating strategy using a polymer–herbal composite of polyvinyl alcohol and neem (Azadirachta indica) extract, deposited on AZ31 Mg alloy via electrophoretic deposition. Electrochemical analyses, including open circuit potential, electrochemical impedance spectroscopy, and potentiodynamic polarization, demonstrated enhanced corrosion resistance for the 5 % polyvinyl alcohol–neem coating, with increased charge transfer resistance and improved surface stability. Contact angle measurements (n = 6) indicated slightly higher hydrophilicity for the 2 % coating; however, the difference was not statistically significant (p > 0.05), suggesting comparable wettability. Scanning electron microscopy and energy-dispersive X-ray spectroscopy confirmed uniform, crack-free coatings with successful composite deposition. No antibacterial activity was observed, likely due to limited release of bioactive compounds from the polymer matrix. Overall, the coating effectively modifies corrosion behavior and surface properties, indicating potential for controlled degradation and improved performance of Mg-based biodegradable implants.