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Trivalent passivation yellow or iridescent

Q. How to make difference between trivalent yellow and iridescent yellow passivation parts?

Santosh Houde
- Pune, Maharashtra
July 28, 2023

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

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

⇩ Related postings, oldest first ⇩

Q. I am doing trivalent yellow passivation over zinc plating in acid zinc plant, but the colour I am getting iridescent colour.
Customer is demanding yellow color. Is it possible to have yellow coloured trivalent passivation?

Avinash Vidhate
owner - Nashik, Maharashtra, India
February 27, 2008

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.

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

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

James Watts
- Navarre, Florida

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

JB Priestley
- Blackwood, Wales
April 23, 2008

thumbs up sign Thank you very much for your guidance.

Avinash Vidhate
- Nasik, Maharashtra, India
November 19, 2010

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