One-step in situ synthesis of graphene oxide/MgAl-layered double hydroxide coating on a micro-arc oxidation coating for enhanced corrosion protection of magnesium alloys

The preparation of excellent anti-corrosion coatings is necessary for practical large-scale applications. In this study, a micro-arc oxidation (MAO) coating was prepared on the AZ31 magnesium alloy in advance. Then, on the basis of the MAO coating, the graphene oxide (GO)/MgAl-layered double hydroxide (MgAl-LDH) composite was prepared by hydrothermal chemical transformation in pure GO solution with the mixed oxide of aluminum and magnesium in the MAO coating as the endogenous cation, without introducing any kind of salts. The chemical states, structural composition and morphology of the GO/LDH-MAO coating were confirmed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The potentiodynamic polarization revealed that 0.1 GO/LDH-MAO coating (3.89 × 10−9 A/cm2) is more resistant to corrosion than MAO coating (9.89 × 10−6 A/cm2) in 3.5 wt% NaCl solution. The organic combination of MgAl LDH and GO can obviously enhance the corrosion protection ability of the coating. This research explored in detail the possible corrosion protection mechanisms regarding GO/LDH-MAO coatings, which supplied the feasibility for enhancing the anti-corrosion performance of MAO coating.