Use nickel as a flux ring

Question

I'm designing an outrunner for a specific application. Rather than use steel to hold the magnets in the flux ring, can pure nickel be used? Nickel is a magnetic material, but has decent oxidation resistance, thus my desire to use it.

Answer 1

It's a little tricky to find useful data (in classic internet search fashion these days..), but here's an old book by NBS on nickel and alloys:

Samuel J. Rosenberg, Nickel and Its Alloys

200 (commercially pure) nickel is generally quite corrosion resistant, but notice it has a lower saturation flux density of 0.75T. You will need more of it, compared to an iron pole piece with say 1.5T B_sat.

I can't seem to find anything about permalloy corrosion resistance; I see a few Chinese suppliers who claim "moderately resistant" to moisture, with no data, which isn't very encouraging. I would expect it's at least not terrible, but it might also be that, due to corrosion-induced stress, the magnetic properties might suffer, for example, so no one bothers to specify its corrosion resistance. But it could also be that I'm not finding any actual hits, beneath the spam of papers on nanoparticle and film materials. You may have better luck asking on Chemistry SE.

Nickel plating is a common and effective process, or chrome or even better zinc (galvanizing), for exposure to mildly corrosive environments like weathering, salt/water immersion, etc. Sacrificial anodes or biasing may also be an option in these conditions. The plating thickness of such processes will most likely not significantly affect your magnetic system (they present a thin air gap), but obviously only you will know that for sure.