Virtue out of necessity I think. Usually they are plated with nickel, then copper then nickel I think as otherwise the material corrodes very quickly. Zinc is probably cheaper?

Perhaps a countersunk fixing could cause an unconstrained magnet to split if carelessly fixed.. ..is the housing to provide support..? 'containment'

Edited By DiogenesII on 18/12/2022 08:24:11

Neodymium is too brittle, fragile and chemically 'active' to be used 'naked'. Hence the magnets are encased for mechanical and chemical protection, and the Zn plate is presumably to protect the case material against corrosion. It looks like the case also acts as a 'pot' magnet's peripheral pole piece, as suggested in the post above.

Edited By Kiwi Bloke on 18/12/2022 08:54:03

I think that neodymium nudity is very rare – every one I've ever seen is nickel plated at least. Once I managed to chip the coating off and the magnet quickly corroded.

**LINK** shows a pot magnet that definitely has a surrounding case – however you can clearly see the gap between the "pot" and the centre pole needed to make sure the flux isn't shorted. There is only a very thin line between the outside "pot" and the magnet face in the Eclipse photo though – but I notice that if you look at the screw hole it does look as if there's a plate at the bottom. You must tell us what you find Michael!

Those Neodym magnets can really shatter into quite sharp shards.

I agree with Ady 1 that Neo magnets from a well known web source are both fragile and rust prone once they are cracked. And some of them arrive like that – but they still work for attaching important (but temporary) papers to a tool box lid or the top of a mill column.

I suspect that as the Neo mix is chosen solely for its magnetic properties, it is not easy to form into shape by old-style methods. My guess is that sintering is used, and a quick flash of zinc is a good way to stop the rust while not affecting the dimensions significantly.

I await news from Michael G about what his magnets comprise when they arrive. If they arrive.

Cheers, Tim

I looked up the magnets on the Zoro website. It describes the plating system and the reason why they are plated. Namely to protect against corrosion.

Andrew.

See P93 of the catalogue I linked to in an earlier post, as well as Robert's link.

Bill

Lee Valley have been selling similar arrangements for years and have a somewhat explanation here.

(LV used to have such a nice, simple website with quite a lot of general background info pages – now it seems to have gone over to "Modern Busy" and if the background is still there, I don't have time to find it.)

Edited By Peter Greene 🇨🇦 on 18/12/2022 19:34:27

Yes … it seems the Eclipse one has a countersunk magnet. Don't really know why that's necessary and it makes the magnet a bit "special".

As an aside to all of this , when salvaging speaker magnets I PART THE FRONT AND BACK PLATES, grind any rivet heads Etc off, clean up, wrap the centre core in tape to fill the coil gap and reassemble. This keeps magnetic dust Etc from bridging the gap and weakening the field. BUT if the magnet is large BE VERY CAREFUL ! When placing on an iron or steel table that you have NOT got the tips of your fingers in the gap, it WILL hurt ! Great for mounting lamps Etc Noel.