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True definition of "Bronze" chromate color for zinc plating

May 1, 2009

Hi! I work for a distributor for hardware and we occasionally outsource plating operations when instructed by a design or engineering standard.

One drawing in particular states that a specific screw should be plated per 1.9.2.3 of MIL-STD-271 (ASTM B633, Ty II, Class 3) except .0003 thick and chromate treatment to be bronze or olive drab in color.

We historically apply the olive drab chromate, but recently received a lot back with what we would call yellow chromate. A similar specification for cadmium states the chromate can range in color from bronze to brown, including yellow, olive drab and forest green. I find no reference to actual colors and definitive color ranges in the Zinc specification.

Is yellow chromate the same as bronze chromate and the terminology simply semantics? Any input is greatly appreciated. I am currently trying to disposition this lot for acceptance or rejection.

Thanks so much!

Loretta Young \O/

Loretta Young
Plating shop customer - Palestine, Texas, USA