Corrosion behavior of Mg-Al LDH film in-situ assembled with graphene on Mg alloy pre-sprayed Al layer

A novel composite coating is designed on Mg alloy by in-situ growing a layered double hydroxides (LDH) on pre-sprayed graphene (reduced graphene oxide) coated Aluminum (G/Al) coating. The pre-sprayed G/Al coating will separate the active Mg alloy matrix from alkaline LDH film-forming solution that avoids the oxidation of Mg and provide the source of Al and graphene for forming the graphene composite LDH coating (G-LDH). The characteristics of the coatings were investigated via X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), energy dispersive spectrometer (EDS), Laser Roman Spectrometer (Raman) and X-ray spectroscopy (XPS), respectively. Besides, the corrosion resistance of the films on magnesium alloy was investigated by using potentiodynamic polarization, electrochemical impedance spectroscopy and immersion test. The results demonstrate that the graphene contained in the intermediate layer is in-situ transferred into LDH film. The in-situ transferred graphene from bottom presprayed G/Al coating seals LDH defects which endows G-LDH with a dense structure. The pre-sprayed G/Al coating on Mg alloy could render a moderate corrosion barrier, and the in-situ grown LDH film play a dual roles involving as corrosion inhibitor and anchoring graphene. The maze blocking effect of graphene coupled with the inhibition-corrosion of LDH endowed this system with superb anti-corrosion performance. (C) 2020 Elsevier B.V. All rights reserved.