Improving structure and corrosion resistance of micro-arc oxidation coatings formed on aluminum alloy with the addition of La2O3

Abstract Ceramic coatings were prepared on 6061 aluminum alloy in electrolytes containing La 2 O 3 particles using the micro-arc oxidation technique. The main work focuses on the microstructure, phase composition, elemental distribution and corrosion resistance of micro-arc oxidation coatings. The results showed that the addition of La 2 O 3 increased the oxidation voltage and promoted the formation rate. Scanning electron microscopy observations indicated that the quantity of discharge micropores decreased and the thickness increased, and thus, the microhardness increased. The X-ray diffraction results showed that the coatings mainly consisted of γ-Al 2 O 3 , α-Al 2 O 3 and SiO 2 . Electrochemical corrosion tests showed that the corrosion resistance of the coated sample with La 2 O 3 increased greatly because the addition of La 2 O 3 significantly reduced the micropores of the coating surface and made the coating thicker, smoother and harder. Hence, the addition of La 2 O 3 can optimize the structure of the micro-arc oxidation coating and improve its corrosion resistance.