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ABSTRACT
To improve the corrosion resistance of the ceramic layer prepared by micro-arc oxidation (MAO) on magnesium alloy, a hydrophobic Mg-Al-Co layered double hydroxide (LDH) coating was fabricated on MAO coated AZ31 magnesium (Mg) alloy by using a simple in-situ growth method. The results showed that the LDH film covered the MAO coating tightly, and it sealed the micro-pores and cracks in the MAO coating successfully. As a result, the LDH film increased the water contact angle of MAO coating from 10.35° to ∼137.21°, and the hydrophobic LDH/MAO composite coating increased the Ecorr of MAO coating from –1.47 to –1.39 V/SCE and decreased the Icorr by about two orders of magnitude. The electrochemical impedance spectroscopy results showed that the LDH/MAO composite coating achieved the largest dimension of capacitive loop and the highest impedance at low frequency compared to MAO coated and uncoated AZ31 Mg alloy. Therefore, the LDH/MAO composite coating could provide long-term protection for Mg substrate from corrosive environment due to its hydrophobic function, ion-exchange ability and barrier effect. This work has significant meaning to the applications of Mg alloys.
GRAPHICAL ABSTRACT
