Electrodeposition of Al coating on Mg alloy from Al chloride/1-ethyl-3-methylimidazolium chloride ionic liquids with different Lewis acidity

Electrodeposition of a metallic Al layer on a Mg alloy from a Lewis acidic Al chloride–1-ethyl-3-methylimidazolium chloride (EMIC) ionic liquid has been carried out at room temperature. The effects of the AlCl3 to EMIC molar ratio, in the range from 50%–50% to 60%–40%, on the electrodeposition characteristics were investigated. Scanning electron microscopy, X-ray energy dispersive spectroscopy, and X-ray diffractometry were used to examine the surface morphology, the chemical composition, and the crystal structure of the deposited layers prepared in the ionic liquids with different AlCl3 to EMIC ratios. The improvement of corrosion resistance of a Mg alloy to the Al surface coating was also evaluated by means of various electrochemical methods. The electrochemical impedance spectroscopic data indicated that while a bare Mg alloy had a polarisation resistance of only 470 Ω cm2 in 3˙5 wt-% NaCl solution, the Al coated sample deposited in the ionic liquid with 60%AlCl3 showed a resistance as high as ...