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| Effect of Forward Cut-off Voltage on Thickness and Corrosion Resistance of Micro-arc Oxidation Film on Surface of ZM5 Magnesium Alloy |
| Received:July 24, 2024 Revised:March 04, 2025 |
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| DOI：10.7643/issn.1672-9242.2025.04.016 |
| KeyWord:magnesium alloy micro-arc oxidation cut-off voltage corrosion resistance |
| Author | Institution |
| LIU Yuanhai |
Aviation Key Laboratory of Science and Technology on Structural Corrosion Prevention and Control, China Special Vehicle Research Institute, Hubei Jingmen , China |
| YIN Qiang |
Aviation Key Laboratory of Science and Technology on Structural Corrosion Prevention and Control, China Special Vehicle Research Institute, Hubei Jingmen , China |
| MENG Jiao |
School of Materials Science and Engineering, Inner Mongolia University of Technology, Hohhot , China |
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| Abstract: |
| The work aims to study the effect of forward cut-off voltage on the thickness and corrosion resistance of micro-arc oxidation (MAO) film prepared on the surface of ZM5 magnesium alloy by bipolar superposition pulse technology. The surface morphology and element distribution of the MAO film were observed and analyzed by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The cross-sectional area was mapped by electron probe micro-analysis (EPMA) to determine the changes in the thickness of the MAO film and the distribution characteristics of various elements under different cut-off voltages. The forward cut-off voltage increased from 380 V to 400 V, 420V and 440V and the thickness of MAO film on the surface of ZM5 magnesium alloys reached 10 µm, 20 µm, 30 µm and 40 µm, respectively. With the increase of film thickness, the distribution of Si, Na, K, O, F, Mg on the surface had no obvious difference. On the cross section of the thicker film, element O was enriched outside the film, and element F was enriched inside, reflecting ion migration and chemical reaction mechanisms inherent to the MAO process. The corrosion resistance of the films increases with the increasing thickness, because the thicker film provides an effective physical barrier against corrosive media. However, the enhancement in electrochemical impedance does not follow a strictly linear relationship with film thickness, likely due to the accumulation of internal stresses and diffusion limitations as the film reaches a critical thickness, leading to microstructural defects such as cracks and porosity, which diminishes the overall protective efficacy of the MAO film. |
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