Composite coatings on a Mg-Li alloy prepared by combined plasma electrolytic oxidation and sol-gel techniques

We present a facile procedure by combining plasma electrolytic oxidation (PEO) technique with sol-gel method to improve the corrosion resistance of magnesium-lithium alloy. A further deposition of a titanium sol-gel layer on the PEO film improves the compactness and anti-corrosion properties. X-ray photoelectron spectroscopy and X-ray diffraction measurements reveal that the PEO coating is composed of MgO and Mg2SiO4, while after sol-gel treatment, the coating contains titania and some low valence titanium compounds. Long-term immersion testing show that the PEO/sol-gel composite coating with better compactness and fewer defects exhibits a superior anti-corrosion property in comparison with PEO alone. (C) 2012 Elsevier Ltd. All rights reserved.