Formation of microarc oxidation coatings on magnesium alloy with photocatalytic performance

Microarc oxidation (MAO) coatings were prepared on AZ91D magnesium alloy in a phosphate electrolyte with and without TiO2 nanoparticles. The effect of TiO2 nanoparticles in the electrolyte on the thickness, surface morphology, composition, structure, corrosion resistance and photocatalytic performance of the coatings were investigated. The appearance and structure of the coatings changed significantly after the TiO2 nanoparticles were added into the electrolyte. The coatings produced in the phosphate electrolyte displayed a grayish white appearance and were mainly composed of MgO and Mg3(PO4)2. However, the coatings formed in the electrolyte with various TiO2 nanoparticles had a blueish color and, additionally, contained the rutile TiO2 and Mg2TiO4. The results of corrosion and photocatalytic measurements show that the coatings formed in the electrolyte with TiO2 nanoparticles not only provided better corrosion protection for magnesium alloy but also exhibited photocatalytic properties.