Preparation of Duplex Film through Microarc Oxidation Coloring and Polymer Plating on Mg-Li Alloy and Its Corrosion Resistance

Microarc oxidation (MAO) coloring and developed polymer plating technique were applied to Mg-Li alloy to get greenish super-hydrophobic film. The formation mechanism, wettability and corrosion resistance of the film were characterized by X-ray photoelectron spectroscopy, OCA35 optical contact angle measuring instrument and potentiodynamic polarization test, respectively. The results show that after MAO coloring Mg-Li alloy with greenish ceramic coating has a water contact angle (WCA) of nearly 0 ° and surface free energy of 74.86 mJ/m2. Then the surface is covered with polymeric film by polymer plating with a WCA of 169.2° and surface free energy of 1.46 mJ/m2. The corrosion resistance of MAO coloring coating is enhanced obviously and has been further improved by duplex modification. Compared to the substrate, the corrosion current density of super-hydrophobic surface from potentiodynamic polarization test in 0.1 mol/L NaCl aqueous solution decreases by three orders of magnitude.