Effects of voltage on electrochemical corrosion behavior of micro-arc oxidation coatings

Abstract

Abstract: The effects of voltage on the electrochemical corrosion behavior of micro-arc oxidation (MAO) coatings formed on pure magnesium were studied by using cyclic voltammetry (CV), potentiodynamic polarization (Tafel) and electrochemical impedance spectroscopy (EIS). SEM was adopted to characterize microstructure of the coatings. The results show that the voltage has significant effects on corrosion resistance of the coatings. With increase of voltage, the corrosion resistance of the coatings gets improved. This may be attributed to the coating's thicker thickness which may provide a good physical barrier against the erosion of the corrosion medium. During the whole corrosion process, the coating prepared in the high voltage experiences three stages: the corrosion medium gradually infiltrates into the coating, then corrosion medium penetrates the coating to the interface between the coating and the substrate, and eventually corrosion products fill into defects such as micropores and microcracks. In contrast, for coatings prepared under low voltage, the electric resistance of both loose layer out of the coating and dense part in the core of the coating decreases gradually with the immersion time prolonging. This results in the corrosion resistance of the coating decreasing, and finally the coating fails completely as a result.

Key words: pure magnesium, micro-arc oxidation, voltage, corrosion behavior

CLC Number:

TG174

MA Ying, ZHANG Qing-ju, AN Ling-yun, WANG Xing-ping, SUN Le, WANG Sheng. Effects of voltage on electrochemical corrosion behavior of micro-arc oxidation coatings[J]. Journal of Lanzhou University of Technology, 2020, 46(3): 1-6.

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