Corrosion resistance of composite coating on magnesium alloy using combined microarc oxidation and inorganic sealing
(1. Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences,
Ningbo 315201, China;
2. School of Material Science and Engineering, Xi’an University of Technology)
Ningbo 315201, China;
2. School of Material Science and Engineering, Xi’an University of Technology)
Abstract: The combined microarc oxidation (MAO) and inorganic sealing process was used to deposit a composite coating to improve the corrosion resistance of AZ31 magnesium alloy. The surface morphologies of the resulting duplex coatings were studied by SEM. Furthermore, the corrosion resistance of the coated Mg alloy substrates was investigated using electrochemical workstation and dropping corrosion test. The results show that the composite coating surface consists of Mg, Si, O and Na. It is difficult to deposit inorganic coating on a thick MAO coating surface. As the composite coating was solidified by CO2 under 175 °C, it exhibits a better corrosion resistance than the MAO monolayer, owing to the thick and compact inorganic coating.
Key words: AZ31 magnesium alloy; microarc oxidation; composite coating; microstructure; corrosion resistance