Preparation and Corrosion Resistance of Dense Cerium Conversion Coatings on Mg-9.95Li Alloy

Dense cerium conversion coating was prepared on the surface of Mg-9.95Li alloy by immersing Mg-9.95Li alloy in cerium nitrate solution with H2O2 and citric acid addition. The chemical composition and morphologies of conversion coatings were characterized by X-ray photoelectron spectroscopy(XPS) and scanning electron microscopy(SEM), respectively. Electrochemical measurements (electrochemical impedance spectroscopy, polarization curves, open circuit potential) were used to analyze the corrosion resistance of the conversion coating. The results indicate that the conversion coating is mainly composed of CeO2 and Ce(OH)(4) cross-linked by citric acid, which becomes denser and more uniform. The dense cerium conversion coating has better corrosion resistance to Mg-9.95Li alloy. The electrochemical impedance reaches 10(4) Omega.cm(2), and the corrosion current density is only 8.86x10(-6) A.cm(-2), which is reduced by two orders than that of Mg-9.95Li alloy.