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Chromate Conversion Coating



Greetings P2Techies:
 
I would appreciate pollution prevention ideas for hexavalent chromium conversion coating. 
 
Are there any possible substitutes (trivalent chromium is not a possible substitute) or methods to reduce losses (no-rinse coating processes?).  I have never seen chromium recovered from the dilute rinsewaters of chromate conversion coating and reused in the process, but I have seen literature references.  Is this alternative practical and realistic?  If so, what is the best technology?
 
Also, Does the chromium rinsed from the coated metal contain significant quantities of trivalent chromium as well as hexavalent chromium?  In other words, during the conversion coating process does the hexavalent chromium at the surface of the coated metal get converted to trivalent chromium to any appreciable extent?
 
Thanks,
 
Rob Michalowicz
Chem Process & Environment Inc.
rob.michalowicz@sympatico.ca