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topic 5420

Electroless Nickel Flaking. Dissimilar Metals Problem?


(2000)

We have an electroless nickel-plated brass nut that is used on one of our products. This nut threads onto a stainless-steel set-screw. The nut plating is flaking off badly when installed. Does anyone know if this has anything to do with the stainless steel touching it, or is it more likely a poor plating job by our vendor? Thanks in advance for assistance.

Joe LaPlaca
signaling - Rochester, New York


(2000)

Galvanic incompatibility is evidenced by corrosion, not by lack of adhesion. Now, I suppose it's vaguely possible that corrosion can be of an under-cutting nature, such that the plating is not attacked but the substrate surface to which it is attached is attacked. But I've personally never seen it and frankly that doesn't sound like the case.

It sounds like the electroless nickel coating is simply not adhering well to the brass substrate. I hesitate to call it "a poor plating job by the vendor" since I don't know who was responsible for what--but I'd say the plating is not adhering to the substrate, and it should be. The brass nut may well be of "leaded" brass and require a special etching process involving hydrofluoric acid to obtain adhesion.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



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