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topic 11677

Electrical switch black carbon buildup on brass material


I have a electrical switch that is showing signs of black carbon build up. The base material is a C260 brass with NO coating. The switch applies only about 1.5N of force and has had a history of failing. Under a microscope the black carbon builds up under the switch and a open circuit condition happens. Any suggestions on a fix or plating to stop this problem?

John Lewis
GHSP - Grand Haven, Michigan


What is the source of the carbon? I suspect the black crud may, in fact, be copper oxide formed by heat from a hot spark. My suggestion: plate the contacts with ruthenium, or if the contact does not abrade the surfaces (no sliding wear) you might be able to get away with gold or palladium.

Dale Woika
Surface Conversion Sciences - Bellefonte, Pennsylvania, USA

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