Corrosion behavior of nano bio coating on AZ31 magnesium alloy by electrophoretic deposition for biomedical application

Magnesium alloy AZ31 is a promising material for biodegradable implants due to its mechanical similarity to bone and its natural degradation in the body, eliminating the need for surgical removal.However, its clinical application is limited by rapid corrosion and susceptibility to bacterial colonization.This study addresses these challenges by applying nano-scale bioactive coatings of hydroxyapatite (HA) and calcium oxide (CaO) onto AZ31 using electrophoretic deposition (EPD).Coatings were deposited under optimized conditions (20 V, 4 minutes, 5 wt%) and evaluated for morphology, thickness, wettability, antibacterial activity, and bioactivity.Single and multilayer coatings showed thicknesses from 21.23 m to over 100 m.SEM and EDS analyses confirmed uniform, crack-free coatings with strong adhesion.Zeta potential measurements above +30 mV indicated stable suspensions, while contact angle measurements revealed significantly enhanced hydrophilicity, especially in triple-layer coatings, which showed a contact angle as low as 1. 58.Antibacterial assays demonstrated strong inhibition of Staphylococcus aureus, with inhibition zones up to 46 mm, while the uncoated alloy showed no antibacterial effect.After 14 days in simulated body fluid, all coated samples exhibited apatite formation, indicating improved bioactivity.The best performance was observed in the triple-layer configuration (CaO + (HA+CaO) + HA), which achieved the lowest corrosion current density (0.0619633 A) and the highest corrosion potential (-895.349mV).These results indicate that this multilayer coating forms an effective protective barrier against corrosion and enhances the biological performance of AZ31.Overall, nano HA/CaO multilayer coatings significantly improve the corrosion resistance, antibacterial properties, and bioactivity of AZ31, supporting their potential use in biodegradable implant applications.