Electrodeposition and nucleation studies of chromium from an acidic ambient temperature chloroaluminate molten salt

The electrochemical reduction of chromium (II) in acidic AlCl3:EMIC (1-ethyl-3-methylimidazolium chloride) room temperature molten salt results in codeposition of aluminum and chromium. Two reduction peaks are observed in staircase cyclic voltammetry, with the first peak significantly smaller than the second. Constant potential deposition in the region of the first reduction peak results in the formation of of Al-Cr deposits consisting of 40 to 50 a/o Cr present as Cr(O) and Cr(II). Constant potential deposition in the region of second peak results in the formation of aluminum rich Al-Cr deposits. Evaluation of the chronoamperometric transient behavior during electrodeposition shows that the codeposit proceeds via a 3D diffusion controlled progressive nucleation on platinum and tungsten with different kinetic control. Gold, as a substrate, gives a decidedly sharper progressive nucleation mechanism which is under kinetic control.