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Has anyone else had issues with rare earth magnets de-laminating? By which I mean the silver coating has peeled off from some of mine and the interior is turning into a powder.
I don't know why this is happening. Is it normal? Have they corroded by coming into contact with something? Is there something I can do to prevent it happening in future?

That's very odd, the silver laminate should not cause concern due to the fact it doesn't really do anything, but the interior falling out? I'd get a refund if I were you, magnets should be completely solid, ones that break apart can cause havoc with electronics

A couple of mine have done that, and it might be to do with the glue I use (Zap-a-gap).
I do have quite a few though, and quality checking would have missed this many by now.

Rare earth magnets are actually made from powder. The powder is pressed and then sintered to form a solid. The magnet is very prone to corrosion, so they are coated to stop the actual magnetic part from corroding, coatings are usually things like chrome, nickle, copper and various alloys of those metals.

So if the internals are turning to powder they might not have been sintered properly or maybe the coating has been damaged and caused the internals to start corroding, but glue shouldn't be strong enough to damage the coating by itself.

So it was probably just bad luck.

Thanks AllSeeingSkink, that's exactly what I needed to know. These magnets are quite old now as well. I have a feeling they may have come into contact with another piece of unidentified metal (came out of a kitchen timer I dismantled), maybe that introduced a flaw.

I've used most of my magnets now anyway so I don't feel too bad about discarding the remaining few and buying a new set. I just wanted to make sure it wasn't some habit of mine causing the issue.

I think if the powder wasn't properly pressed, sintered and treated before being coated they can corrode from the inside out. It's not something I've seen personally but if they're old magnets maybe that's what's happening. It shouldn't happen with good quality magnets though, magnets in (for example) motors or hard drives last damned near forever.

If the magnets are chromed, then there are 3 coatings on it (zinc, nickel then chromium ) - more often than not, it's just nickel plating over zinc, and that will peel off from humidity alone. (Dad was an electroplater)


(Nickel plated door handles shouldn't be used on bathroom doors for this reason. The plating flakes off - It can be polished up almost as shiny as chrome, but is nowhere near as durable)

 chromedog wrote:
If the magnets are chromed, then there are 3 coatings on it (zinc, nickel then chromium ) - more often than not, it's just nickel plating over zinc, and that will peel off from humidity alone. (Dad was an electroplater)


(Nickel plated door handles shouldn't be used on bathroom doors for this reason. The plating flakes off - It can be polished up almost as shiny as chrome, but is nowhere near as durable)

I think most of the cheaper magnets from reputable suppliers are actually Nickle - Copper - Nickle coated, though I'm not sure about the really cheap ones from China and whatnot. Chrome ones would be Ni - Cu - Ni - Cr, but those would be the more expensive types.

Though it doesn't really matter from the point of view of this thread as I doubt the OP has the capability to determine which metals were used In the end all we know is the coating is failing; either the coating itself is failing or the magnet is degrading from the inside out and the coating is just peeling off with it.