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"Corrosion problem Nickel plated Phosphor Bronze"


Q. We currently have a corrosion problem on our so-called limit switch contacts. They are a SAE CA510 .010" thick Phosphor Bronze material that we have nickel plated. Our nickel plate call out is BRIGHT (not sure in the industry what this stands for as far as thickness, etc.) nickel and uses the ASTM B322 [affil. link to spec at Techstreet]-85 as far as cleaning the parts beforehand. The contacts sit in a plastic housing and there only contact is with another contact with the same properties. Our question is should we specify a different Nickel finish or possibly there is some other material that could serve our purposes that wouldn't need to be plated and that would run around the same cost (if not cheaper) but have the same material properties as the Phos. Bronze? Possibly, we just need to specify a thicker nickel plate or something of that nature.


Steffen J. Weech
Chamberlain Group, Inc. - Nogales, Arizona USA


A. Traditionally, bright nickel is a sulfate nickel that has brighteners added.

Electroless nickel will cost a bit more, but is more wear resistant and is more corrosion resistant.

If I understand your use, 0.0005" would probably be minimal.0.0010" would be better and very harsh conditions would use 0.0015".

James Watts
- Navarre, Florida

Phosphor bronze components made from strip becomes blackish after nickel & tin plating


Q. We make components from phosphor bronze strips. They are first plated with nickel ( 4- 5 microns) and then tin plated (12 - 15 microns). Recently we are observing very odd phenomenon. 2-3 hours after plating, edges of components appear blackish. Black colour starts increasing as time passes. We are not able to investigate reason for this. If we plate copper in same tin bath, no problem is observed. Kindly guide us in this matter.

Zankar Desai
- Vadodara, Gujarat, India

A. Hi Zankar. Short of doing some photomicrograph investigations of those edges, my guess has to be that your nickel plating has very high tensile stress and is pulling away at the edges, taking the tin plating with it, and exposing the phosphor bronze to corrosion.

Are you doing mandrel bend tests on the strips to see that the nickel adheres without cracking? And can you get micrograph photos done?

Please take a look at thread 49424 which also addresses issues related to plating of phosphor bronze. Good luck.


Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

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