Trivalent passivation yellow or iridescent

A. Hi Santosh,
More words please. I don't want to misunderstand you and then mislead you.
Luck & Regards,


Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Trivalent chromating is still very highly proprietary technology, with widely differing approaches taken by the various vendors, so it's hard to say anything that is both definitive and generic, Avinash. But I think the "thick film" chromates are more yellow than iridescent, while the "thin film" chromates are more iridescent but are dyed to make them yellowish.

But please view this as an opportunity for leadership! If at all possible, as the expert, please try to sell your customer on moving away from that amber yellow look. The yellow color was never dye; rather, it was the characteristic inherent color of toxic, carcinogenic, hexavalent chromium. Trying to insure that today's greener parts are carefully disguised to look like they are still steeped in toxins may not be the best idea :-)

In the old days, glassware that contained poisons had a skull and crossbones etched into the glass, and it was quite attractive glasswork -- but artistic & decorative as it was, we don't emboss today's milk bottles with that pattern; similarly, perhaps we shouldn't label today's greener finishes as poison by dyeing them to look exactly like the poison.

A. Some people are using dyes after the trivalent to get the "old" yellow color.

A. Either reduce temperature to 20 °C or apply lacquer topcoat.