HOME FAQs BOOKS JOBS: Help Wanted Suggestions you are here: Hotline/Forum => Letter 20093

Hexavalent Chromium Level in Passivation after Bleaching

+++

Dear All,

Just looking for confirmation, if I have a zinc alloy casting which is colour passivated yellow, which is then bleach sealed is the level of hexavalent chromium still the same after the bleaching process. I am trying to estimate the amount of hexavalent chromium on our parts.

Regards,

Chettan Karsan
- Newmarket, England

November 14, 2009

i don't really know much about the passivation process but I do know hexavalent chrome turns to triavalent at 500 degrees.

doug samson
- greenwood, South Carolina

November 14, 2009

Hi. I can't comment on Doug's response, but back to the original question, no, the level of hexavalent chromium is not the same after bleaching.

The bleaching process is not chlorine bleach, it's just hot water that leaches out a good portion of the chromate. The fainter color of the parts is because there is less yellow hexavalent chromate on them after it's been leached out.

Note, though, that bleached/leached chromate will probably not pass RoHS requirements, which are for very little hex chrome.

Regards,

Ted Mooney, P.E.
finishing.com
Brick, New Jersey

ANSWER or FOLLOW UP POST an unrelated QUESTION HOT Topics

Disclaimer: It is not possible to diagnose a finishing problem or the hazards of an operation via these pages. All information
presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The
internet is largely anonymous; some names may be fictitious and some recommendations may be deliberately harmful.

If you are seeking a product or service related to metal finishing, please check these Directories: