A promising method for electrodeposition of aluminium on stainless steel in ionic liquid

A promising method for aluminium deposition was proposed by using AlCl ₃/[bmim]Cl (1 -butyl-3-methylimidazolium chloride) ionic liquid as electrolyte. By using this novel method, the volatile and flammable organic solvent systems and the high corrosive inorganic molten salts with high temperature can he substituted, and the deposit microstructure can be easily adjusted by changing the current density, temperature and electrolyte composition. The study was performed by means of galvano-static electrolysis and the optimum operating conditions were determined based on the systematic studies of the effects of current density, temperature, molar ratio of AlCl ₃ to [bmim]Cl, stirring speed and deposition time on the quality of deposited coatings. The electrical conductivities of electrolytes were also investigated as a function of temperature (298-358 K) and molar ratio of AlCl₃ to [bmim]Cl (from 0.1:1 to 2.0:1). Dense, bright and adherent aluminium coatings were obtained over a wide range of temperature (298-348 K), current densities (8-44 mA/cm² ) and molar ratio (1.6:1-2.0:1), Results from the analysis of crystal structure show that all of the electrodeposits exhibit a preferred (200) crystallographic orientation. Temperature has significant influence on the crystallographic orientation and there does not appear to be an apparent impact of current density on it. Analyses of the chronoamperogram.s indicate that the deposition process of aluminium on stainless steel was controlled by three-dimension nucleation with diffusion-controlled growth and there is a conversion from progressive nucleation to instantaneous nucleation.