Effect of positive bias on properties of chitosan coating prepared on micro-arc oxidation surface of Ti-6Al-4V alloy by electrophoretic deposition

Chitosan (CS) coatings produced via electrophoretic deposition (EPD) have been widely applied to improve the bioactivity of implants, but the low-coating adhesion strength and water electrolysis during electrophoresis weaken the resulting coatings. Accordingly, we initially fabricated porous micro-nano structures on the Ti-6Al-4V alloy by micro-arc oxidation (MAO) to serve as interlocking sites. Then a CS coating was prepared via EPD, during which, an asymmetric AC pulse voltage was applied. The adverse impacts of hydrolysis were effectively avoided; thus, a flat MAO/CS coating was eventually prepared. The effect of positive bias during EPD on the surface morphology, chemical compositions, wettability, corrosion resistance, and in vitro bioactivity of the coating had been analyzed. The results indicated that the as-obtained composite coating significantly enhanced the corrosion resistance of the substrate in simulated body fluids (SBF). After immersion in SBF, the MAO/CS coating was found to induce the formation of a bone-like apatite layer on the alloy surface, indicating excellent bioactivity. When the positive bias reached 70 V, the as-prepared coating showed the best performance in all aspects. All results suggest that the modified alloy is very promising for biomedical applications.