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<p>Micro-arc oxidation coatings with different MgF<sub>2</sub>/MgO mass ratios were fabricated on magnesium alloys in KF-KOH electrolyte. The effects of mass ratio on the microstructure and corrosion resistance of coatings were studied, and the results showed that the thickness of compact layer first increases and then decreases with the mass ratio of MgF<sub>2</sub>/MgO varying from 0.1 to 7.6. As the mass ratio of MgF<sub>2</sub>/MgO reaches 0.9, MgO and MgF<sub>2</sub> phases are interlaced and uniformly distributed in coatings. The microstructure of the coating with MgF<sub>2</sub>/MgO of 0.9 effectively utilizes the blocking and preheating effects between MgF<sub>2</sub> and MgO, inhibiting the intense eruption of breakdown melt and promoting the growth of compact layers. Therefore, the coating possesses the thickest compact layer (~&#xa0;3.5&#xa0;μm). Electrochemical tests reveal that the coating with MgF<sub>2</sub>/MgO of 0.9 exhibits the best corrosion resistance with the corrosion potential of –&#xa0;596 mV, which is 907&#xa0;mV and 887&#xa0;mV larger than those of the coatings with MgF<sub>2</sub>/MgO of 0.1 and 7.6, respectively. Furthermore, electrochemical impedance spectroscopy measurements showed that the coating with MgF<sub>2</sub>/MgO of 0.9 has a higher impedance modulus. Its impedance of the compact layer increases to ~ 6 times compared to those of the coatings with MgF<sub>2</sub>/MgO of 0.1 and 7.6, respectively.</p>

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Influence of MgF2/MgO Mass Ratios on the Microstructure and Corrosion Properties of Micro-arc Oxidation Coatings on Magnesium Alloys

  • 期刊论文

  • 发表日期：

    2025年4月9日

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  • Yujie Wang,
  • Qingxia Zhang,
  • Peng Zhang,
  • Yunhui Du,
  • Kun Liu,
  • Pengfei He,
  • Changqing Li

摘要

Micro-arc oxidation coatings with different MgF2/MgO mass ratios were fabricated on magnesium alloys in KF-KOH electrolyte. The effects of mass ratio on the microstructure and corrosion resistance of coatings were studied, and the results showed that the thickness of compact layer first increases and then decreases with the mass ratio of MgF2/MgO varying from 0.1 to 7.6. As the mass ratio of MgF2/MgO reaches 0.9, MgO and MgF2 phases are interlaced and uniformly distributed in coatings. The microstructure of the coating with MgF2/MgO of 0.9 effectively utilizes the blocking and preheating effects between MgF2 and MgO, inhibiting the intense eruption of breakdown melt and promoting the growth of compact layers. Therefore, the coating possesses the thickest compact layer (~ 3.5 μm). Electrochemical tests reveal that the coating with MgF2/MgO of 0.9 exhibits the best corrosion resistance with the corrosion potential of – 596 mV, which is 907 mV and 887 mV larger than those of the coatings with MgF2/MgO of 0.1 and 7.6, respectively. Furthermore, electrochemical impedance spectroscopy measurements showed that the coating with MgF2/MgO of 0.9 has a higher impedance modulus. Its impedance of the compact layer increases to ~ 6 times compared to those of the coatings with MgF2/MgO of 0.1 and 7.6, respectively.