Characterization
of Imidazolium Chloride Ionic Liquids
Plus Trivalent Chromium Chloride for Chromium Electroplating
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Abstract
A series of mixtures consisting of
the ionic liquids (ILs) 1-ethyl-3-methylimidazolium
chloride, 1-butyl-3-methylimidazolium chloride, and 1-hexyl-3-methylimidazolium
chloride ([emim][Cl], [bmim][Cl], and [hmim][Cl], respectively) and
trivalent chromium chloride have been prepared. Physicochemical and
electrochemical properties of these mixtures have been studied and
the potential applications of these mixtures for chromium electroplating,
as an alternative to the conventional hard chromium electroplating
processes using hexavalent chromium baths, have been examined. To
optimize the transport properties of the mixtures, different amounts
of ultrapure water were added to the Cr(III) salt–IL mixtures,
although the ultimate goal is to reduce or eliminate water. As shown
previously for choline chloride/Cr(III) salt mixtures, we found that
the physicochemical and electrochemical properties of the mixtures
are affected by the relative water content. Our preliminary electroplating
results show that these types of Cr(III) salt–IL mixtures could
be promising alternatives to Cr(VI) containing baths for chromium
electroplating applications with the advantage of avoiding the use
of highly toxic hexavalent chromium