Zinc-plating trivalent and hexavalent difference

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I'm working at a competitive furniture company as Quality Engineer (In-coming).
I want to know the easiest way to differentiate between zinc-plating part trivalent and hexavalent.Other than we do some detail inspection that need certain time to get the result,can it be confirmed visually?If can,please explain to me.
There is a possibility for me to overlook the trivalent and hexavalent condition when it comes to small part like screws,nuts etc.

Zul Hilmi
Engineer - Kuala Lumpur, Malaysia

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As far as I know, you cannot just look at the part and tell the two apart. There may be some sophisticated instrumental method I am not familiar with.

This question has come up before on the board. A sample of the lot of parts needs to be leached to remove the conversion coating, and the leachate tested for hexchrome with a colorimetric test.

Dave Wichern
- The Bronx, New York