Local Electrochemical Corrosion Properties of a Nano-SiO2/MAO Composite Coating on an AM60B-Mg Alloy |
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| Authors: | Xiaoyu Yang Yu Mo Ting Dai Jie Zhao Yanhong Gu |
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| Affiliation: | 1.School of Mechanical Engineering, Beijing Institute of Petrochemical Technology, Beijing 102617, China; (X.Y.); (Y.M.); (Y.G.);2.Beijing Academy of Safety Engineering and Technology, Beijing 102617, China |
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| Abstract: | In order to improve the corrosion resistance of the automotive AM60B-Mg alloy, a nano-SiO2/MAO composite coating was prepared on the surface of the alloy. The electrochemical properties were studied in an 80 °C corrosion environment using potentiodynamic polarization tests. Local Electrochemical Impedance Spectroscopy (LEIS) was used to study the corrosion mechanisms of coating defect zone. The microstructure and phase of the samples were observed by confocal laser microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). Macroscopic electrochemical test results showed that the impedance of the nano-SiO2/MAO coating was much higher than that of the MAO coating, by about 433 times. Local electrochemical test results showed that the minimum impedance of the nano-SiO2/MAO coating was 1–2 orders of magnitude higher than the maximum impedance of the MAO coating. The defective SiO2/MAO coating still had high corrosion resistance compared to the defective MAO coating. A physical model of local corrosion mechanisms was proposed. |
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| Keywords: | AM60B-Mg alloy micro-arc oxidation composite coating corrosion mechanism LEIS |
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