Correlation between Electric Parameters and Microstructural Properties of LZ91 Mg Alloy Coated by Micro Arc Oxidation

• Published in: International journal of electrochemical science Vol. 13; no. 6; pp. 5709 - 5722
• Main Authors: Jian, Shun-Yi, Lee, Jeou-Long, Lee, Hung-Bin, Sheu, Hung-Hua, Lin, Ming-Hsien, Shih, Yu-Tong, Chen, Chi-An, Chang, Jun-Kai, Ger, Ming-Der
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.06.2018
• Subjects: Corrosion resistance; LZ91 Magnesium alloy; Micro arc oxidation; Salt spray test; Corrosion resistance; LZ91 Magnesium alloy; Salt spray test; Micro arc oxidation
• ISSN: 1452-3981; 1452-3981
• DOI: 10.20964/2018.06.11

Micro arc oxidation (MAO) coatings are prepared on LZ91 Mg alloy at different voltages (400, 450 and 500 V). A DC, uni-polar and bi-polar power mode is used, respectively, in this work. The aim of this study is to investigate the effect of electrical parameters (power mode and voltage) on the morphology, microstructure and the corrosion behavior for LZ91 alloy. The element distribution, morphology, and corrosion resistance were studied by Electron Probe X-ray Micro-analyzer, Scanning Electron Microscope, potentiodynamic polarization in 3.5 wt.% NaCl solution and salt spray test. It is found that the increase of voltage make the coatings more porous and thicker. The applied power mode (DC, uni-polar and bi-polar modes) shows a significant influence on the coating morphology and corrosion resistance. Analysis of SST and potentiodynamic polarization technique on the samples show that the corrosion resistance of the MAO coated samples is much better than that of the bare LZ91 Mg alloy. The MAO coating prepared at 450 V under bi-polar power has smallest porosity, and hence yields best corrosion resistance on LZ91 Mg alloy.