Coatings on Permanent Magnets

Not familiar with those terms. OK black epoxy I know. Ask a magnet maker.

Find them on Search GlobalSpec.

My experience is with sintered Neodymium and with bonded neodymium magnets. I have found that for sintered Neo magnets, NiCuNi is good for approx. 40 hrs in a standard salt fog test, while NiCuNi + epoxy will go 200+ hours. For bonded Neo, epoxy alone is adequate and if it is done well it will go 200+ hours but may be slightly less. I don't think NiCuNi is possible for bonded magnets, and I have not tried epoxy alone for sintered magnets. One other option which works quite well for bonded magnets is parylene coating.

I have not tested any other type of magnet other than ceramic which requires no coating for corrosion protection. They do not corrode.

I've bought some of these Neodymium-Iron-Boron magnets to play around with. The cheaper ones are Nickel plated and the plating eventually comes off. I suspect a tiny hole in the plating lets moisture in and the magnet material corrodes causing the plating to unbond.

I've also bought some gold plated ones, and I haven't seen any of them lose their plating.

I would be interested in knowing a good procedure for resealing the Nickel plated ones.