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topic 0385

Filtering of spent chrome stripping bath

A discussion started in 1996 and continuing through 1996.
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We have a small tank plating system for the gold plating of chrome plated objects. We first remove the chrome with NaOH, activate with HCl acid and plate with cyanide gold. Is there a way to filter out the chrome stripping bath so that it would not have to be totally replaced? Someone told us to use some sort of rosin bag but we have not heard of that.

Any ideas?

Rob Henry - tech manager
Gold Touch, Inc.
supporting advertiser  
Cleveland, Ohio

gold touch


There are two generally accepted ways to strip chrome, Rob, depending on circumstance and substrate: a dip in HCl, or electrolytically in a caustic tank. I have seen these electrolytic tanks still functional even when lemon yellow from hex chrome, so maybe you don't have to dump it quite yet.

Hexavalent chrome is anionic (CrO4-2) rather than cationic like most other metals so it is theoretically possible to remove the chrome with a simple anion exchange resin. But whether you will have attack, or gumming up of the resin, or chemical imbalances, and so on in the real world is something you will either have to test or rely on the experience of the vendor. Good luck.

Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

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