Speciation, physical and electrolytic properties of eutectic mixtures based on CrCl₃·6H₂O and urea.
The electrodeposition of chromium is a technologically vital process, which is principally carried out using aqueous chromic acid. In the current study, it is shown that eutectic mixtures of urea and hydrated chromium(III) chloride provide a liquid which reduces the toxicological issues associated with the current aqueous Cr(VI) electroplating solution. Using EXAFS, mass spectrometry and UV-Vis spectroscopy, it is shown that chromium is present predominantly as a cationic species. Conductivities are higher than for most comparable ionic liquids. It is shown that the electrodeposition of chromium is electrochemically reversible, with a current efficiency much higher than in aqueous electrolytes. Surface tension and density measurements indicate that hole theory is a valid model to describe transport properties in these liquids. Bulk Cr deposits are not macrocrystalline but they are generally crack-free. The deposits have a hardness of 600 ± 10 Vickers and, as such, are comparable to deposits from aqueous systems.
Chemistry Department, University of Leicester, Leicester, UK LE1 7RH. Andrew.abbott@le.ac.uk.
Andrew P
AP
Abbott
Azeez A
AA
Al-Barzinjy
Paul D
PD
Abbott
Gero
G
Frisch
Robert C
RC
Harris
Jennifer
J
Hartley
Karl S
KS
Ryder