Corrosion behavior of superhydrophobic micro-arc oxidation/graphene oxide/stearic acid composite coating on magnesium alloy under different salt spray test conditions
[Introduction]The corrosion of a superhydrophobic composite coating on the surface of magnesium alloy under three salt spray test conditions i.e.standard neutral salt spray test at 35 ℃,neutral salt spray test at 45 ℃,and simulated seawater salt spray test was studied.[Method]The micro-arc oxidation(MAO),electrodeposition of graphene oxide(GO),and self-assembly with stearic acid(SA)were carried out with AZ91D magnesium alloy as the substrate to form a superhydrophobic MAO/GO/SA composite coating.[Result]The composite coating showed superhydrophobicity in all three salt spray tests prior to the formation of corrosion pits,with a water contact angle of approximately 150°.Following the appearance of corrosion pits,the water contact angle of the specimen under standard neutral salt spray condition was decreased slower than that under other salt spray conditions.The results of polarization curve measurement showed that the corrosion current density of the composite coating was three orders of magnitude lower than that of the magnesium alloy substrate.After 192 hours of salt spray test under different conditions,the corrosion current density of the specimen with the superhydrophobic composite coating was lower than that of the AZ91D magnesium alloy substrate.However,the corrosion current density of the simulated seawater salt spray test specimen was increased at the fastest rate,and the composite coating on this specimen was the first to be corroded.[Conclusion]The superhydrophobic MAO/GO/SA composite coating has excellent corrosion resistance,protecting the magnesium alloys effectively from corrosion in corrosive media and reducing the corrosion rates of magnesium alloys.
magnesium alloymicro-arc oxidationgraphene oxidestearic acidcomposite coatingsuper-hydrophobicitycorrosionsalt spray test
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