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Yellow Zinc/Silver Zinc?

Hi,
I am wondering if somebody can tell me the difference between Silver zinc vs. Yellow zinc?

Steve Fisher
fastener company - Leola, Pennsylvania, USA
December 29, 2008

Hi, Steve. Many fasteners are zinc plated because it is inexpensive, corrosion resistant, and generally a good finish for the purpose. The zinc deters red rust, i.e., rusting of the steel fastener. But the zinc itself can corrode with an unsightly "white rust" and a chromate conversion coating stops that. The chromate can be clear (silver), blue, yellow, olive drab, or black.

In the old days of hexavalent chromates, a yellow color indicated a rather heavy and protective coating whereas the clear was much thinner and offered less protection. These days though, where most chromates are RoHS compliant trivalents, the color is not really an indication of protective value -- it's just aesthetics.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
December 29, 2008

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