Preparation and characterization of ceramic/metal duplex coatings deposited on AZ31 magnesium alloy by multi-magnetron sputtering

The multi-magnetron sputtering technique was applied to deposit ceramic/metal duplex coatings on AZ31 magnesium alloy to improve its surface properties. Two different protective coating structures, Al2O3/Al and Al2O3/Ti, were prepared in this study. SEM, AFM, EDS, FEISEM and AES were used to investigate the coatings' morphology and composition. These obtained coatings were very uniform and took on a compact morphology in micro-regions. The AZ31's surface mechanical property was improved by coating. The Al2O3/Ti coating showed better improvement than the Al2O3/Al coating at the lower load. In the corrosion test, Al2O3/Al coating protected the substrate effectively in 3.5 wt.% NaCl solution. The damage in this electrolyte was mainly due to the pores and cracks existing in the coating.