Micro‐Arc Oxidation of Aluminum Alloys: Mechanism, Defects, and Corrosion Resistance

The micro‐arc oxidation (MAO) is widely used to improve the corrosion resistance of aluminum alloys by forming an in situ ceramic coating of alumina. However, defects such as pores, cracks, and cavities are inevitable forms during fabrication, significantly reducing corrosion resistance and limiting the further application of MAO coatings. Addressing this issue requires a thorough understanding of defect formation mechanisms before optimizing preparation parameters. In view of this, the mechanisms underlying the discharge channels, film growth, and the defects formation are systematically reviewed. Then effects of coating defects on corrosion performance and the recent strategies for defect control are summarized. Finally, the challenges in defect control faces and future trends are proposed, aiming to enhance the understanding and extend of the application of MAO on lightweight valve metals.