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Zinc Chromate Corrosion caused by insufficient cure time?

We manufacture Electrical Connectors and are having a corrosion issue with some Copper Terminals that are Zinc Chromate Plated at an outside vendor. We bring them in house and take them right to the assembly line (into plastic housings), within hours of receipt. Within 24 hours we have corrosion on the surface of the Terminals as we moisturize the assembly for customer use. Could we be using these Terminals too quickly before they are cured or are we looking at the wrong thing? These parts are fed via feeder bowls into position for assembly into the plastic housings and our thought was the edges of plating could be disrupted by this action creating thin areas in the plating.

Bob DeRoss
Product Designer - Pinellas Park, Florida
2007

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2007

Bob,

Usually the hexavalent chromate gets its hardness after 48 hrs. I wonder if you are using trivalent or hexavalent. Yo should check with your plating supplier how long time it takes to get a resistant chromate surface. And if the temperatures you use afterwards, in the plastic injection process are adequate for the chromate.

Saludos

Guillermo Castorena
Jobshop - San Luis Potosi, Mexico