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Coffee color spots on the zinc plated surface of forged parts




2006

In about 3-4 days coffee spots appear on the zinc plated surface of not machined forged parts . We are zinc plating machined forged parts, and we are using the next;

1. Zinc alkaline plating bath
2. Trivalent chrome conversion coating
3. Top Seal

We are using patent products from DIPSOL

Our problem are coffee spots that appear 3-4 days after zinc plating in some parts, but on not machined surface areas.

In stamping parts or machined bar parts we don't have such a problem

We thank you your kind attention to this matter

ADRIAN MENDOZA MARTINEZ
Electroplating Service - TOLUCA, MEXICO


Most likely your brown (not coffee) spots are caused by little or no zinc in rough areas. The more roughness you have, the less cleaning and metal you get inside the pores. Your chromate only makes it worse. I would say your options would include better cleaning and thicker plating. Saludos y suerte amigo!

Guillermo Marrufo
Monterrey, NL, Mexico
2006




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