Electrodeposition of Aluminum From AlCl3-BMIC Ionic Liquids in High Gravity Fields

In high gravity fields, the electrodeposition of aluminum (Al) on stainless steel electrodes from AlCl₃-BMIC ionic liquids with 2:1 molar ratio were studied at 75℃. Analyses of the cyclic voltammetry indicate that the deposition of Al is a diffusion-controlled quasi reversible process either in normal or in high gravity fields and the high gravity coefficient (G) has no influence on the diffusion coefficient of Al ions. The electrodeposition process is strengthened with the intensification of convection of electrolyte in high gravity fields. The results of the chronoamperograms suggest that the deposition process of Al is instantaneous nucleation in both normal and high gravity fields. The density of crystal nucleus increases from 8.02*10⁸ cm^-2 in normal gravity field to 20.34*10⁸ cm^-2 with G=200, which means high gravity field could accelerate nucleation to enhance the electrochemical reaction rate. The influence of high gravity coefficient (G) on surface morphology and crystal structure of the Al coatings was also investigated. SEM results show that high gravity field can refine the grain and avoid dendrite, resulting in good adhesive coatings. XRD analysis reveals that all of the electrodeposits exhibit a preferred (111) crystallographic orientation, enhanced with the increase of G.