Influence of Voltage on the Corrosion and Wear Resistance of Micro-Arc Oxidation Coating on Mg–8Li–2Ca Alloy
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Calcium phosphate (CaP) coatings were prepared on Mg–8Li–2Ca magnesium alloy by micro-arc oxidation (MAO) in an alkaline Na3PO4–Ca[C3H7O6P] base solution at the different applied voltages. Scanning electron microscope and X-ray diffraction were employed to characterize the microstructure and phase composition of the coatings, respectively. The corrosion resistance of the coatings was assessed by potential dynamic polarization curves, electrochemical impedance spectroscopy and hydrogen evolution experiment in simulated body fluids solution. The friction and wear properties were evaluated by friction and wear testing machine. The results demonstrate that the coating surface is porous and mainly composed of MgO, Ca5(PO4)3(OH) and CaH2P2O5. With the increase in voltage, the corrosion resistance and wear resistance of the MAO coating are both enhanced. The corrosion current density of the MAO coating decreases about two orders of the magnitude compared to the substrate. Additionally, wear and corrosion mechanisms are discussed.
KeywordsMagnesium alloy Micro-arc oxidation Electrochemical impedance Wear mechanisms
This work was supported by the National Natural Science Foundation of China (Nos. 51671063, 51771060 and 51871068), the Key Laboratory of Lightweight and high strength structural materials of Jiangxi Province (No. 20171BCD40003), the Research Fund for the Doctoral Program of Higher Education (No. 20132304110006), Heilongjiang Province Natural Science Foundation (No. ZD2017010), the Fundamental Research Funds for the Central Universities (No. HEUCFG201834), the Harbin City Application Technology Research and Development Project (Nos. 2015RQXXJ001 and 2017RAQXJ032), the Science and Technology Innovation Project (No. 009-031-001).
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