Corrosion and bacterial resistance of MAO-PA composite coating on AZ91 magnesium alloy

Abstract

The antibacterial properties and corrosion resistance of magnesium-based materials are critical to the safety and reliability of medical equipment. As a promising metallic biomaterial for such applications, magnesium-based materials must address significant concerns regarding the potential for corrosion of various components and bacterial contamination in operating rooms and other medical environments. Ensuring that medical equipment remains safe and dependable is paramount, as these issues can compromise the effectiveness and integrity of the devices. This study evaluated the synergistic effects of the micro-arc oxidation (MAO) process combined with phytic acid (PA) treatment on AZ91 alloys in basic media. The assessment focused on surface topography, electrochemical response, immersion experiments, and antibacterial properties, comparing the results with those of the bare substrate and MAO-based coatings. The results indicate that adding 4 g of nano-TiO₂ per liter to the MAO electrolyte generates MgO, MgSiO₄, and TiO₂ on the surface. These compounds can act as a barrier, preventing rapid degradation and thereby slowing the corrosion rate. At 60 °C, a 60-min treatment with phytic acid (PA) yields the best corrosion resistance, which is an order of magnitude higher than that of MAO-based coatings. Furthermore, this treatment reduced the survival rate of Escherichia coli under various wavelengths of ultraviolet light.