Electrochemical studies of metallic chromium electrodeposition from a Cr(III) bath

In this work we describe the electrochemical behavior of an ionic liquid formed between choline chloride (ChCl) and chromium chloride hexahidrated (CrCl3 center dot 6H(2)O) in the ratio of 2.5:1 containing 20 wt.% of added ultrapure water, using cyclic voltammetry and chronoamperometry. The reduction of Cr(III) occurs in two steps, Cr(III) to Cr(II) and Cr(II) to Cr(0), respectively. The first step is controlled by diffusion. For the first time a thorough study of the nucleation of chromium from Cr(III) ionic liquid solutions is described. Furthermore for less cathodic potentials there is a diffusion control of nuclei growth. For more cathodic potentials the lattice incorporation of adatoms to the growing nuclei is the limiting process. The additive free bright chromium deposit obtained is formed by semi-spherical nuclei. The effect of hydrogen evolution is only observed for E < - 1.90 V. (C) 2013 Elsevier B.V. All rights reserved.