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Zinc/chromate dust

We are purchasing steel bushings that are plated with zinc and have a clear trivalent chromate coating. There is a shiny, powdery residue on the parts and the packaging when we receive the parts. Is this customary for this finish?

Mark Noll
electronic connectors - Myrtle Beach, S.C., U.S.A.
2003

It's not customary, and is probably not proper, although it does happen. I believe that drying out of the chromate because of baking or drying too soon or at too high a temperature is one possibility. Another possibility,since you report that it is shiny, is that it is tiny chips of the zinc plating caused by excessive abrasion. The zinc should not readily chip off, but depending on the shape and surface finish of the parts it certainly can happen if the parts bump each other excessively.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2003

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