In-situ synthesis of ZnO/CuO nanocrystals in micro-arc oxidation coatings for enhanced antibacterial performance and corrosion resistance of aluminum alloys

In this study, micro-arc oxidation (MAO) technology was used to prepare composite ceramic coatings incorporating ZnO and CuO nanocrystals (denoted as Zn-MAO and Cu-MAO coatings, respectively) on an aluminum alloy surface, which exhibit both corrosion resistance and antibacterial performance. The microstructure, chemical composition, and phase structure of the composite coatings were characterized. The corrosion resistance of the coatings was evaluated by electrochemical impedance spectroscopy (EIS), and the antibacterial performance was assessed via tests against Escherichia coli and Staphylococcus aureus. The results indicate that both composite coatings bonded well with the substrate, and ZnO and CuO nanocrystals were formed in-situ within the coatings. The average particle size of the ZnO nanocrystals was about 5 nm, while that of the CuO nanocrystals was about 20 nm. Both composite coatings significantly enhanced the corrosion resistance of the substrate, reducing the corrosion current density by more than one order of magnitude. The Cu-MAO coating exhibited an antibacterial rate of >99% against both Escherichia coli and Staphylococcus aureus . Analysis suggests that although the Zn element content in the Zn-MAO coating was higher, the CuO nanocrystals in the Cu-MAO coating released more metal ions within 24 hours, and the Cu 2+ possesses higher antibacterial activity, leading to a significantly superior antibacterial performance of the Cu-MAO coating compared to the Zn-MAO coating.