Ionic Liquid Plating


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 Q. Can ionic liquid plating be used as a replacement for conventional plating? How do the cost, environmental advantages/disadvantages, efficiency stack up with classic hard chrome plating? Are there any commercial sources using this technology? T.L.


A. For those of you not familiar with this newer plating technique, I briefly discussed it in my October 2008 column. Here are some excerpts from that column:

“An ionic liquid is made up of only cations and anions. For you non-chemists out there, a cation is a positively charge special, for example, Cu+2 and an anion is a negatively charged ion, for example SO4-2. In the case of ionic liquids, the cations are usually organic and the anions inorganic.
Again, looking at our example ions, typically we write the formula for copper sulfate as CuSO4. CuSO4 is a molecule but under the right conditions we can get the molecule to break apart into ions:

CuSO4 —> Cu+2 + SO4-2

If CuSO4 exists essentially in the form to the right of the arrow you would have an ionic liquid. In the case of CuSO4, a very high temperature would be required. This is considered a molten salt. With ionic liquids, room temperature is adequate. For example, tetraethylammonium nitrate is made up essentially of 100% ions. 


Many of these materials are sensitive to water, and their properties will change if they are diluted with water.


What about the use of these materials in plating? Like many things in the development stage, they are extremely promising. They essentially replace water and increase the chemical reactivity, which can lead to more efficient metal finishing processes. Since they are electrically conductive and non-inflammable, they are good replacement for many of the classic hydrocarbon based solvents.”


Here’s a recent paper that discusses the use of these materials in plating: short.pfonline.com/ionics.


I have no information regarding the pros and cons of this technology versus conventional chromium plating, nor do I have information about the commercial use of these materials.


I’m hoping that our readers will have some information on this and will share it with us.