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Effect of Electrolyte on Mechanical and Corrosion Properties of AZ91 Cast Magnesium Alloy Coated by Plasma Electrolytic Oxidation Method  

Kim, Bo-Sik (Graduate Student, Korea Aerospace University)
Lee, Du-Hyung (Graduate Student, Korea Aerospace University)
Chang, Si-Young (Department of Materials Engineering, Korea Aerospace University)
Publication Information
Journal of Korea Foundry Society / v.29, no.5, 2009 , pp. 233-237 More about this Journal
Abstract
The effect of electrolyte on mechanical and corrosion properties of AZ91 magnesium alloy by plasma electrolytic oxidation (PEO) method was investigated. The coating layers formed in the silicate and the aluminate electrolytes showed porous structures. The small pores were randomly distributed on the coatings formed in aluminate electrolyte while the coatings formed in silicate electrolyte showed much bigger pores. In the aluminate electrolyte, the coatings were composed of Mg, MgO and $MgAl_2O_4$, whereas Mg, MgO, $MgAl_2O_4$ and $Mg_2SiO_4$ were identified in the coatings formed in silicate electrolyte. The hardness of coatings in the silicate electrolyte was higher than that of coating grown in the aluminate electrolyte. The AZ91 alloy coated in the silicate electrolyte had higher tensile strength and elongation than that coated in the aluminate electrolyte. In addition, the coatings formed in the silicate electrolyte showed much better corrosion resistance compared to the coatings formed in the aluminate electrolyte.
Keywords
Plasma electrolytic oxidation; Electrolyte; AZ91 alloy; Hardness; Tensile Property; Corrosion resistance;
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