Electrodeposition of Bright Al Coatings from 1-Butyl-3-Methylimidazolium Chloroaluminate Ionic Liquids with Specific Additives

The electrodeposition of aluminum (Al) on copper (Cu) substrate was investigated in [Bmim]Cl/AlCl 3 (33.3/66.7 mol%) ionic liquid using three pyridine derivatives, nicotinic acid, methyl nicotinate, and 3-methyl pyridine as additives at 303 K, respectively. It was found that bright Al coatings could be electrodeposited with nicotinic acid and methyl nicotinate as additives. SEM and XRD characterizations revealed that the bright coatings were very smooth, composed of nanocrystalline and with a strong (200) preferential orientation. By contrast, a matte and lusterless Al coating was obtained from the ionic liquid with 3-methyl pyridine. Furthermore, the effect of the three additives was investigated by means of cyclic voltammetry, chronopotentiometry and Raman spectroscopy. It was demonstrated that nicotinic acid and methyl nicotinate could absorb on electrode surface more easily and thus served as very effective brighteners producing highly uniform and smooth Al coatings. However, 3-methyl pyridine had no such effect.