Morphology and Corrosion Resistance of MAO/Mg-Al LDH Composite Film Obtained on LA103Z Mg-Li Alloy at Different Temperatures

Abstract

ABSTRACT A solution of Al(NO3)3.9H2O and NaOH was used to perform Mg-Al LDH plugging treatment on the LA103Z magnesium-lithium alloy micro-arc oxidation ceramic layer. The effect of treatment temperature on the micro-arc oxidation ceramic layer structure and corrosion resistance was studied. The formation mechanism of Mg-Al LDH film and corrosion mechanism of the film layer were discussed. The results show that the sealing essence of Mg-Al LDH is that the Mg2+ obtained by dissolving the MgO component of the MAO film layer is combined with OH– in the hydrothermal solution to form a layered Mg(OH)2, the formation of LDH tends to be inside the pores. In the lower temperature range, the temperature increase is conducive to the increase and thickening of the LDH layer and the film layer is dense and corrosion resistant. In the higher temperature range, the increase in temperature is conducive to the increase in the size of the LDH layer. The layer is loose and coarse, and the corrosion resistance is reduced. The composite film is the densest at 90oC, and its insulation and corrosion resistance are better than the composite film obtained at other temperatures, the MAO film and the substrate. GRAPHICAL ABSTRACT