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"Chromekill 6A"


We are intersted in hearing from anyone that has used a probuct called Chromekill 6A to treat our waste waterat PH 12 ( to change hexavilent to trivalent chrome ). The trivalent chrome is percipitated out. The waste water appears to be clear but remains green in colour. Is this the result of still holding trivalent chrome in solution?

Dave Stratton
- Tasmania, Australia


The only material that will reduce chrome at that high a pH, that I know of, is sodium hydrosulfite, also called sodium dithonite. And, you will likely have to reduce the pH to some where in the 9.5 - 10.5 range to get good coagulation of the Cr(OH)3 precipitate.

dave wichern
Dave Wichern
Consultant - The Bronx, New York


We have used chromekill 6a in our electro cleaner on of our our plating lines with much success. We use tri-chrome to plate,but when we have rejects,we run them back through the line and blow the chrome off in the electro cleaner wich forms hex-chrome,so we throw approximately 10 # of chromekill into the cleaner and it turns the hex into tri. As for your color change I'm not absolutely sure.....but....I do know in our electro cleaner when it has to much hex chrome in it,it turns a yellowish color,after adding the chromekill it goes back to the original brownish color. Hope this helps ya out a bit!


Brian C. Gaylets
- Scranton, Pennsylvania, U.S.A.


Firstly, if memory serves me correct, Chromekill is an Enthone product. Its chemical composition is/was a blend of reducing sugars and sodium hydrosulfite(the formula may have been changed in recent years to make it less "dangerous"). It is normally used in plating lines to reduce hexavalent chromium in cleaners and in post chrome plating rinses. This product and sodium hydrosulfite, are listed as explosive materials by the U.S. DOT and OSHA and consequently has fallen out of use by many who could find non hazardous replacements.

However, as Dave points out, the only material for your circumstance would be sodium hydrosulfite. This generic product would be much less costly for your application than a proprietary (I I sell the later!)

Gene Packman
process supplier - Great Neck, New York

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