Improved corrosion resistance of magnesium alloy with a surface aluminum coating electrodeposited in ionic liquid

A metallic aluminum (Al) layer was successfully electrodeposited onto a magnesium (Mg) alloy in a Lewis acidic aluminum chlofide-1-ethyl-3-methylimidazolium chloride (AlCl3-EMIC) ionic liquid under a galvanostatic condition at room temperature. Effects of deposition current density on material characteristics of the deposited layers were explored by means of a scanning electron microscope and an X-ray diffractometer. In addition. the improvement in corrosion resistance of the Mg alloy due to the AI coating was evaluated by electrochemical measurements and a salt spray test. The electrochemical impedance spectroscopic data indicated that a bare Mg alloy had a polarization resistance of only 470 Omega cm(2) in 3.5 wt % NaCl solution, whereas the Al-coated Mg sample showed its resistance as high as 8700 Omega cm(2) in the same environment. Moreover, it was also found that the At layer deposited at a lower current density was more compact and uniform when compared to that deposited at a higher current density; consequently, this coating revealed a superior protection capability for the Mg substrate against corrosion. (C) 2008 The Electrochemical Society.