Re: chemical needed to remove contaminate ions from chrome plating bath?

Hi Dan,

I can't think of a specific chemical for your purpose, but possibly a complexing agent (EDTA or similar) might help.

The desirable properties of this complexing agent would be:

1) Formation constant for Cu⁺, Cu²⁺, Fe²⁺ and Fe³⁺ ions is much larger than the formation constant for Cr⁶⁺

2) The Fe/Cu complex is insoluble in water (so can be filtered out)

Having a larger formation constant for Fe/Cu than Cr, indicates that the complexing agent will attach itself to the Fe/Cu ion in preference to the Cr ion.

I didn't manage to find a specific chemical with these properties, but if you have the time and patience to sift through tables of data at a local university library, and find formation constants, you might find a chemical that is of use to you.

If you need more explanation of anything, feel free to email me.

Jonathan Feldman
University of Technology, Sydney
dr_chemistry@mad.scientist.com