ABSTRACT

Plasma electrolytic oxidation coatings were formed in Na₂C₄H₄O₆–KF–Na₂SiO₃ system on AZ91D magnesium alloy by controlling the single-pulse square-wave and bipolar pulse square-wave, respectively. Potentiodynamic polarisation (PD), electrochemical impedance spectroscopy (EIS) and electrochemical noise measurement (EN) were employed to investigate their corrosion behaviour in 3.5% NaCl solution. The results show that with bipolar pulse mode for PEO process, the growth rate of PEO coating on magnesium alloy first decreased and some micropores were present inside the PEO coating. With the increasing oxidation time, the PEO coating became much homogeneous and the porosity of the coating decreased largely, and the corrosion resistance of PEO coating was enhanced. The use of the bipolar pulse mode is beneficial to the improvement of the compactness and corrision performance of magnesium alloy with PEO treatment for the higher voltage stage and longer oxidation time.

摘要

_{在 Na 2} C ₄ H ₄ O ₆ -KF-Na ₂ SiO ₃中形成等离子电解氧化涂层AZ91D镁合金系统分别通过控制单脉冲方波和双极脉冲方波。动电位极化 (PD)、电化学阻抗谱 (EIS) 和电化学噪声测量 (EN) 被用来研究它们在 3.5% NaCl 溶液中的腐蚀行为。结果表明，采用双极脉冲模式进行PEO工艺，镁合金上PEO涂层的生长速度首先降低，PEO涂层内部出现了一些微孔。随着氧化时间的增加，PEO涂层变得更加均匀，涂层的孔隙率大大降低，PEO涂层的耐腐蚀性能增强。