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Trivalent passivation yellow or iridescent



(-----) February 27, 2008

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

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 do think the "thick film" chromates are more yellow than iridescent, while the "thin film" chromates are more iridescent.

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 not dye; rather, it was the characteristic color of toxic, carcinogenic, hexavalent chromium. Trying to make sure that today's greener parts are disguised to look like they are still steeped in toxins may not be a good idea :-)

In the old days, glassware that contained poisons had a skull and crossbones embossed into the glass, and it was rather attractive glasswork. But artistic and decorative as it was, we'd rather not emboss today's milk bottles with that pattern; similarly we'd rather not label today's greener finishes as poison by dyeing them the color of the poison.

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


February 29, 2008

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

James Watts
- Navarre, Florida
^


April 23, 2008

Either reduce temperature to 20 °C or apply lacquer topcoat

JB Priestley
- Blackwood, Wales
^

----
Ed. note: If impersonating a police officer gets you thrown in the pokey, impersonating a screenwriter should get you locked into the theatre for a bad movies festival :-)



November 19, 2010

Thank you very much for your guidance.

Avinash Vidhate
- Nasik, Maharashtra, INDIA
^

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