Main > IONIC LIQUIDS. > Choline.Cl Metal Ionic Liquids > Co.: UK. S. (Brand/Mfg./Patents) > CrCl3.6H2O+Choline.Cl > Uses > ElectroPlating > Description
Last year, Co. s researchers reported that chromium can be efficiently electrodeposited onto stainless steel from a eutectic of choline chloride and hydrated chromium(III) chloride, CrCl3·6H2O, mixed in the molar ratio of 1:2. They also found that the addition of lithium chloride to the mixture results in the deposition of black nanocrystalline chromium films that are corrosion resistant and crack free.
"Hard, wear-resistant, low-friction coatings are required for critical applications in civil and military aerospace, in the automotive and marine industries, and for industrial hydraulics". "For example, hard chromium coatings are essential for hydraulic rams in everything from aircraft landing gear to excavators."
Conventional chromium plating technology suffers from a major disadvantage: It employs hexavalent chromium, Cr(VI), which is highly toxic and carcinogenic. In addition, the reduction of Cr(VI) requires acid media, and the current efficiency of the process is low.
The eutectic mixture of choline chloride and CrCl3·6H2O is significantly less toxic than Cr(VI) salts. Co. is now using the eutectic mixture to develop a chromium electroplating process that has a current efficiency of more than 90%.
"This reduced power consumption reduces the cost and the overall environmental impact of the chromium-plating process". "Hydrogen evolution is negligible, as we do not use aqueous solutions, and it is therefore possible to produce crack-free, highly corrosion resistant deposits. The process should allow thinner deposits to be formed, thus reducing overall material and power consumption even further."
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