Al2O3 coating MAO coating MAX phase Ni-Fe-Co-P-CeO2 composite coating PVD PVD coating Research & information: general Ti2AlN W-Cr-C coating Zn-Al diffusion layer aging mechanism aluminum alloy AlMg6 aluminum foam anodizing layers apatite boride-based cermet carburization cathodic protection cavitation chemical properties coating coating selection cold galvanized coating composite coatings compression test corrosion corrosion behavior corrosion mechanism corrosion mitigation method corrosion protection