In-situ incorporation of polydopamine surface modified bioactive glass nanoparticles into a plasma electrolytic oxidation coating on biodegradable AZ31 Mg alloy: A study of bioactivity and corrosion performance

Magnesium alloys are promising candidates for next-generation biodegradable biomaterials. However, their poor corrosion resistance has limited their medical applications. In this study, to improve the bioactivity performance and control the degradation rate of an AZ31 Mg alloy, anodic oxide coatings containing bioactive glass (BG) were created on the alloy using plasma electrolytic oxidation (PEO). First, BG nanoparticles were synthesized through the sol-gel method and surface-modified with polydopamine (BG/PDA). These nanoparticles were then dispersed in an alkaline phosphate electrolyte and incorporated into the coatings grown using unipolar and bipolar waveforms. According to EDS results, incorporation of BG/PDA nanoparticles was higher when the bipolar waveform was applied. Electrochemical impedance spectroscopy revealed that the coatings significantly enhanced the corrosion resistance of the AZ31 Mg alloy, with the BG/PDA nanoparticle-containing coatings demonstrating the lowest degradation rate during long-term immersion. These coatings achieved the highest faradic resistance of ∼ 12 kΩ.cm² after 28 days of immersion. The incorporation of BG and BG/PDA nanoparticles enhanced the bioactivity performance of the coatings, facilitating hydroxyapatite formation on the coating surface. Based on the results, the newly developed BG-coated alloy shows promising potential for biomedical applications.