Metal finishing Q&As since 1989

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How Do I Remedy Suspected El Ni on El Ni Galling?

I have often used electroless nickel plating on low carbon or case hardened tubular components. I currently have two tubular members which slide over each other. We specified (without much thought) electroless nickel on both members and now experience galling or a like phenomena especially when the parts have no tarnishing or when assembled after a vacuum baking to increase the hardness. I am coming to suspect that I will need to use dissimilar platings or find an conversion coating. The parts are sometimes lubricated and sometimes used without lubrication. They can see high contact pressures which is one reason we opted for the El Ni with baking. Any insight would be helpful. We would like to keep the platings in the same color range. As mentioned they are tubular 10:1 l/d.

Thanking responses in advance...

George Dewey
- Palatine, Illinois, USA
2001

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Hi phosphorus electroless nickel (10% P or higher) against Mid-Phosphorous electroless nickel has worked without galling. A better solution, but more expensive, is to use electroless nickel-PTFE (or CFx EN) for one EN surface. the lubricating particles codeposited with the Electroless nickel provide an anti-galling combination. (PTFE is generic for "Teflon", a trade name of E I Dupont Co) CFx is similar to PTFE but will withstand higher operating temperatures.

Don Baudrand
Consultant - Poulsbo, Washington
(Don is co-author of "Plating on Plastics" [on Amazon or AbeBooks affil links]
           and "Plating ABS Plastics" [on Amazon or eBay or AbeBooks affil links])
2001

EN vs EN has a coefficient of friction of .45, En vs Steel is .38 hard chrome vs hard chrome is .43 hard chrome vs steel .21 is the winner. I do not have any data on EN vs. ENPTFE. My experience with ENPTFE is you have to try it out you can not predict how it will work.It is well worth looking into.

Todd Osmolski
- Charlotte, North Carolina, USA
2001