Summary for chrome passivation Discussion
Chrome passivation is the focus keyphrase here, and the thread asks whether a chrome passivation stage is needed after zinc phosphating on galvanized steel, since some people report finishing problems after the final step. Dannu Malpani describes a five-stage pretreatment sequence: cleaner, rinse, zinc phosphate, rinse, and chrome passivation, and asks about the drawback of the chemical treatment. The answer given by "Luck & Regards" says chrome post dips or final rinses are excellent from a performance standpoint, but they leave hexavalent chromium on the part. The practical concern is therefore not process performance, but the health and environmental issue associated with hexavalent chromium, which is identified as a carcinogenic toxin. The thread does not say that chrome passivation is technically unnecessary after zinc phosphating; rather, it highlights the tradeoff between good performance and the hazard of residual chromium on the finished part.
Q. There are generally 5 stages pre-treatment process for Galvanised steel. (Cleaner, rinse, Zinc phosphate, rinse, Chrome passivation). I came to know that people face some finishing problems after stage 5 i.e., Chrome passivation. What is the drawback of using Chemical treatment i.e., chrome passivation stage?
Dannu Malpani
agra university – Agra, UP, India
2004
A. Hi Dannu. Chrome post dips (final rinses) are excellent from a performance standpoint, but they leave hexavalent chromium (a carcinogenic toxin) on the part.
Luck & Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
Need quick confidential answers? $25
Need project assistance? $100/hr.
2004