Electrodeposition of Al-Ni intermetallic compounds from aluminum chloride-N-(n-butyl)pyridinium chloride room temperature molten salt

Electrodeposition of aluminum-nickel intermetallic compounds (particularly Ni3Al) has been carried out onto platinum and mild steel cathodes from a 2: 1 (mole ratio) aluminum(III) chloride-N-(n-butyl)pyridinium chloride (BPC) molten bath saturated with nickel(II) chloride at room temperature. A singl e phase of Al-Ni alloy is difficult to obtain by controlled-potential and c ontrolled-current methods; however, it can be obtained by pulse current pla ting. The electrodeposition of nickel from an AlCl3-BPC-NiCl2 (6.14:3.07:0. 09 mole ratio) molten bath occurs via an instantaneous nucleation mechanism in the very initial stage of the crystal growth. The deposition reaction m echanisms of nickel in this molten bath are revealed by electrochemical ana lysis. The experimental Tafel slope of 42 mV dec(-1) and the calculated tra nsfer coefficient (<(<alpha>)over bar>(c))of 1.5 suggest that the rate dete rmining step is a charge transfer reaction of an adsorbed bare monovalent c ation to the metallic state. The effect of the cycle regime on the electrod eposition of Al-Ni alloys has been investigated. The current efficiency for the deposition of alloys is about 99%. (C) 2001 Elsevier Science BN. All r ights reserved.