Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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Trivalent Yellow Chromate
I am an engineer in charge of fasteners. I have been having some questions and issue surrounding our finish specifications. Currently we call out "Zinc with Yellow Chromate, Hexavalent Chromium Free"
We have been getting some conflicting responses from our suppliers that say that this is not possible from some and others say that they can dye the chromate but it does not get a dark enough color. Others seem to simply be lying to us and sending us hex and telling us its trivalent.
The reason that we want the yellow color rather than simply calling out a salt spray spec is that our customers use the color as a kind of color coding for grade. We supply hardware stores and auto stores and the customers have come to expect a grade 8 bolt to be yellow and a grade 5 bolt to be zinc colored.
So my question is:
Is a good yellow color attainable with a hexavalent free chromate conversion coating?
Mechanical Design Engineer - Colmar, Pennsylvania, USA
October 11, 2011
December 18, 2011
Yes, possible
But you can add yellow to blue passivation and then turned to yellowish cr 3 passivation without any cr 6
blue passivation contains cr/co, this elements amount is also important for correct yellow passivations
regards
- Istanbul, Turkey
Yes , it is possible
you can get different colours by using dyes
- Istanbul, Turkey
January 8, 2012
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