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Discolorization of tin-plated brass without barrier layer

We recently have an issue with brass terminals plated with tin. The customer does not specify an undercoating. We are now receiving complaints about discoloration and "flaking". We have been producing these parts for a couple of years without issue. New QE at the customer and now there is an issue. The part is processed through an oven (by the customer) at ~300° F for a short period of time. The condition shown in the picture is after the oven treatment.

57350-1 57350-2

Any thoughts on why the discoloration is greater now then before?
Is the picture showing "flaking" really flaking or simply the zinc migration?
Thank you.

Mario Pagliuzza
stamper of questionable part - Addison, Illinois, USA
June 21, 2011

Hi,

The major problem would be the zinc migration, one has to do a copper undercoat before going for Tin plating on Brass substrate, or you may face this problem, also it may contaminate the Tin bath.

Praveen Kumar
plating process supplier
Mumbai, India
June 28, 2011

We are facing the same problem, did you figure out what happened?

Thanks

John Bow
- Florence, South Carolina
February 29, 2012

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