Ceramic coatings were fabricated on AZ91D magnesium alloys by micro-arc oxidation in silicate system with Al2O3 colloid addition. The influences of adding time and amount on chemical composition, microstructure and corrosion resistance of the MAO ceramic coatings were studied. The results show that the ceramic coating formed with adding Al2O3 colloid at the late period of total oxidation time, 6 min (about 3/5 of the total oxidation time) presents the best corrosion resistance. And the corrosion rate decreases evidently with the increase of Al2O3 colloid dosage. However, the corrosion resistance is hardly influenced when the Al2O3 colloid exceeds 20% of the volume of total electrolyte.

micro-arc oxidation; Al2O3 colloid; composite ceramic coating; corrosion resistance

Taiyuan University of Technology