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Trivalent Plating turns pink when insert molded with phenolic plastic

April 12, 2013

Q. Hello all and I hope that you can help me out with my problem.

I am a screw manufacturer who is selling a plated product to a customer. This part has .0002 zinc with a Hi-Corrosion Trivalent chromate finish. When my customer molds this insert into the finished product it has a pink residue on it. (Please see the photo)

I have talked to my local plating houses along with the chemical supplier with no ideas of what is causing this. I did send out the residue to a lab to have it tested and was told that the main chemical in the residue was calcium carbonate.

I have already tried two different chromates from my plater and I am in process of having a third plating lot done at a different plater. My customer has stated that they do not have this issue when they use hexavalent chromate.

I was wonder if anybody has any ideas of what is causing this and a workaround with trivalent chromate.

Thanks for you time.

Ken Janik
- Franklin Park, Illinois

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April 22, 2013

Q. These parts where not dyed. The original finish was .0002 zinc, clear trivalent chromate. The chromate is clear but with a "blue bright" tint.
The pink that you see happened after the parts were molded.

Ken Janik
- Franklin Park, Illinois

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