Enhanced corrosion protection of AZ31 magnesium alloy by duplex plasma electrolytic oxidation and polymer coatings

摘要

The corrosion behaviour of an AZ31 magnesium alloy coated with plasma electrolytic oxidation(PEO), polymer and a combination of them was assessed by electrochemical impedance spectroscopy (EIS) in 0.1M NaCI solution. The polymer coating was applied on a just cleanedsurface (without any special preparation) and also on PEO treated magnesium substrate. Whilethe polymer coated and the mere PEO treated magnesium alloy specimens lasted less than 50 hin the EIS tests, the specimens with the duplex coating (PEO+ polymer) successfully resisted1000 h in the EIS tests without showing any degradation. The improved adhesion of the polymercoating in presence of the PEO layer and the effective sealing of the pores in the PEO coating withthe polymer were responsible for the enhanced corrosion resistance. The synergistic beneficialeffect of the duplex coatings on the corrosion behaviour was also witnessed in the salt spray tests.