Effects of temperature and water content on physicochemical properties of ionic liquids containing CrCl3·xH2O and choline chloride

The effects of temperature and water addition on some physicochemical properties of liquid mixtures containing chromium chloride (as hexahydrate salt), choline chloride and water in the molar ratio of 1:0.5:x (x = 6, 9, 12, 15 or 18) are systematically investigated. The measurements of density, viscosity, surface tension and conductivity have been performed for the temperatures between 25 and 80 °C. An increase in the water content leads to decreasing density, viscosity and surface tension and to increasing conductivity. The obtained results are interpreted in terms of hole theory; the average hole sizes for the liquid mixtures are calculated. The activation energies for viscous flow and conductivity are stated to decrease with water content. Chromium films can be electrodeposited from the liquid mixtures under consideration. Uniform, grey Cr coatings with a relatively high current efficiency (reaching 60-90%) can be obtained if the water content is close to intermediate values (x = 9-12) and at temperatures of ca. 40-50 °C.