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Zinced + Blue Passivated

Hello,

Someone please teach to solve my question. Actually I was confusing about treatment "zinced + blue passivated" and treatment "trivalent blue". Both of them are similar, same effect or totally different? Please help, and thank you.

Gary Chang
Metal industries employee - Balakong, Selangor, Malaysia
June 10, 2011

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Hi, Gary.

Steel components cannot be directly chromate conversion coated ("passivated"). When you hear about it, someone is implying or inferring that the parts were plated with zinc, zinc alloy, or cadmium plated first. Thus "zinc'd + blue passivated" means zinc plated followed by chromate conversion coating, with the chromate being a light pastel blue.

Most, but not all, blue chromate conversion coatings are "trivalent" in recent years to conform with RoHS standards for freedom from hexavalent chromium. But it should always be clearly specified. Slang may be necessary for brevity in some mileaus, but it is context dependent; the minute you take it out of the context in which it was understood, and ask what it means outside of that context as an independent entity, there are 101 opportunities for misunderstandings and mistakes :-)

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
June 10, 2011