Effect of Hydrothermal Treatment Time on Microstructure and Corrosion Behavior of Micro-arc Oxidation/Layered Double Hydroxide Composite Coatings on LA103Z Mg-Li Alloy in 3.5 wt.% NaCl Solution

The micro-arc oxidization (MAO) ceramic layer on an LA103Z Mg-Li alloy substrate was treated with a hydrothermal treatment at 90 degrees C for various times. The effect of the hydrothermal treatment time on the microstructure and corrosion behavior of MAO/LDH composite coatings in 3.5 wt.% NaCl solution was investigated, and the mechanism of hydrothermal film formation and corrosion was discussed. The results show that MgO on the surface of the MAO ceramic coating was partially dissolved during the hydrothermal treatment, and the released Mg(2+)ions combined with OH(-)ions in the hydrothermal solution to form Mg(OH)(2)nanosheets, which were deposited on the surface of the ceramic coating and its pores. The hydrogen evolution rates of the MAO/LDH composite coatings rank as MAO/LDH-24 h < MAO/LDH-18 h < MAO < MAO/LDH-12 h. A MAO/LDH composite coating had the minimum weight loss, which proves that the MAO/LDH composite coating prepared by MAO and hydrothermal treatment has better corrosion resistance than a single MAO ceramic layer and adds long-term corrosion resistance to the magnesium alloy.