Benzoxazine/Micro‐Arc Oxidation High‐Temperature‐Resistant Composite Coating With Superior Corrosion Protection Performance on Magnesium Alloy

ABSTRACT In this study, to seal the pores of a micro‐arc oxidation (MAO) coating, benzoxazine (BZ) is used to form a highly heat‐resistant MAO/BZ composite coating with excellent anti‐corrosion performance on a magnesium alloy. The as‐prepared BZ coating, which has a static water contact angle of 111.52° ± 2.6°, is bonded firmly to the MAO coating and can withstand a temperature of 300°C. The results of electrochemical tests indicate that the composite coating prepared by BZ with a concentration of 40% demonstrates a low corrosion current density of 9.01 × 10 −12 A cm −2 in a 3.5 wt.% NaCl aqueous solution. Moreover, the composite coating exhibits an outstanding corrosion resistance after a neutral salt spray test for 82 days. Furthermore, it is concluded that an increased concentration of BZ can significantly increase the coating thickness with a dense curing crosslinking structure, which is a key factor in the corrosion protection of MAO coatings.