Concentrated Aqueous Solution of Chromium Dichloride for Chromium Metal Electrodeposition

Abstract

Concentrated electrolytes have been found to play host to stellar phenomena previously unachievable in solutions at diluted or moderate concentrations. In an attempt to explore the possible utility of concentrated electrolytes in electroplating, this study reports the electrodeposition of Cr metal using a concentrated aqueous solution of Cr(II) (4.0 mol kg⁻¹) without additives. Target aqueous CrCl₂ solutions are characterized by UV–visible spectroscopic and ionic conductivity measurements. The influence of concentration, current density, and agitation on Cr metal deposition is discussed on the basis of cyclic voltammetry, galvanostatic electrolysis, X-ray diffraction, and scanning electron microscopy. Here, electrolysis of the concentrated electrolyte at medium current densities (20 mA cm⁻²) under agitation is found to engender dense metallic α-Cr deposits with high adhesivity to the substrate. The results further show that increasing the current density to expedite the deposition process promotes the involvement of an impurity phase and deposition of the δ-Cr phase.