Microarc oxidation coatings containing TiC and NbC on magnesium alloy

Microarc oxidation (MAO) coatings were formed on AZ91D magnesium alloy in zirconate–phosphate electrolytes with and without the addition of titanium carbide (TiC) and niobium carbide (NbC) particles. Surface morphologies, structures, compositions and corrosion resistance of the MAO coatings were investigated. The MAO coating formed in the based electrolyte was mainly composed of MgO, Mg2Zr5O12 and some amorphous phases. TiC and NbC particles in the electrolyte were incorporated and uniformly distributed in the MAO coatings. Both particles increased the thickness and compactness of the MAO coatings. Electrochemical measurements results indicated that the TiC and NbC particles in the electrolyte improved the corrosion resistance of the MAO coating, and those formed in the electrolyte with NbC particles showed the best corrosion resistance.