Investigation of rare earth sealing of porous micro-arc oxidation coating formed on AZ91D magnesium alloy

• Published in: Journal of rare earths Vol. 30; no. 12; pp. 1293 - 1297
• Main Authors: Laleh, M., Kargar, Farzad, Rouhaghdam, A. Sabour
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.12.2012
• Subjects: AZ91D magnesium alloy; AZ91D镁合金; Ce bath; Coating; corrosion resistance; Corrosion tests; Electrochemical impedance spectroscopy; Magnesium; Magnesium base alloys; micro-arc oxidation; oxide coating; Porosity; Rare earth metals; rare earths; Sealing; 多孔; 密封处理; 微弧氧化膜; 扫描电子显微镜; 氧化物涂层; 电化学阻抗谱; 稀土; AZ91D magnesium alloy; micro-arc oxidation; Ce bath; oxide coating; corrosion resistance; rare earths
• ISSN: 1002-0721; 2509-4963
• DOI: 10.1016/S1002-0721(12)60223-3

Magnesium and its alloys have been used in many industries, but they are reactive and require protection against aggressive environments. In this study, oxide coatings were applied on AZ91D magnesium alloy using micro-arc oxidation （MAO） process. Then, in order to seal the pores of the MAO coatings, the samples were immersed in cerium bath for different times. The surface morphologies and compositions of the coatings were analyzed by scanning electron microscopy （SEM） and X-ray energy dispersive spectroscopy （EDS）, respectively. The corrosion behavior of the coatings was investigated with electrochemical impedance spectroscopy （EIS） and potentiodynamic polarization tests in 3.5 wt.% NaCl solution. The amount of the porosity of the coating was measured by electrochemical method. It was found that the sealing treatments by immersion in cerium bath successfully sealed the pores of the MAO coatings. The results of the corrosion tests showed that the MAO coating which was sealed in Ce bath for 10 min enhanced the corrosion resistance of the substrate significantly. Furthermore, this coating had the lowest amount of the porosity among the coatings.