Electrodeposition mechanism of aluminium from aluminium chloride-N-(n-butyl)pyridinium chloride room temperature molten salt

Electrodeposition of aluminium has been carried out by controlled-current a nd controlled-potential methods from acidic aluminum(III) chloride-N-(n-but yl)pyridinium chloride (BPC) molten bath at room temperature. The electrode position of aluminium from acidic AlCl3-BPC melt occurs via instantaneous n ucleation mechanism in the very initial stage of the crystal growth. The de position reaction mechanisms of aluminium in the acidic AlCl3-BPC molten ba th are revealed by electrochemical analysis. The experimental Tafel slope o f 20 mV dec(-1) and the calculated transfer coefficient (alpha(c)) of 3 sug gest that the rate determining step is a chemical reaction involving the re lease of the complexing agents via three consecutive single electron transf er steps. The influence of various conditions on electrodeposition and the morphology of the electrodeposited layers have been investigated by X-ray d iffractometry and scanning electron microscopy. On increasing the current d ensity smaller particle size and better adhesiveness of the electrodeposite d layers have been obtained. The cathodic current efficiency for the deposi tion of Aluminium is about 99.8%.