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I gone done a foolish thing; I got my set of spherical (⌀ 5 mm) neodymium magnets covered in of (what is presumably iron based) ferromagnetic silt/sand particles.

chain of spherical magnets with black silt/sand at the joints, watch glass with larger particles in background

With some difficulty, I've been able to remove most of the sand sized particles (by grabbing them with some needle-nose pliers). But, the silt sized particles are much harder to remove — as the magnets are very strong, and the particles are very small.

How can I effectively removed these small ferromagnetic particles from the magnets?

Ideally I'd like to keep the silt, but my priority is to clean the magnets.
Obviously I don't want to permanently demagnetise the magnets.

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    $\begingroup$ You can try rolling them in an adhesive or dip them in wax and then break off the wax. Clay might work. $\endgroup$
    – Stevan V. Saban
    Commented Nov 9, 2022 at 4:21
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    $\begingroup$ You might also consider caulking or rubber cement. Any matrix that can trap the particle and be peeled off after curing $\endgroup$
    – Stevan V. Saban
    Commented Nov 9, 2022 at 4:31
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    $\begingroup$ My condolences. You could try putting them into a bucket with a sieve so the magnets can't get away but the sand can, and then blasting it with a pressure washer. I know from experience that shop air won't work. At least, not shop air at at around 150psi. $\endgroup$
    – DKNguyen
    Commented Nov 9, 2022 at 5:31
  • $\begingroup$ Try wiping them off with damp cloth. $\endgroup$
    – Ján Lalinský
    Commented Nov 9, 2022 at 6:24

2 Answers 2

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I have found that using an adhesive can work well to remove small pieces of dust like this. I have used packing tape to pull the particles off of small neodymium magnets.

I found this method on the K&J magnetics FAQ page, link here.

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I have now tried using the suggestions provided (both in the comments and in the other answer), and wish to share my results:

  • The adhesive tape (a cloth tape) that I used was effective at removing the silt. But, I found that this is not a great method, because it is not particularly easy to manoeuvre the magnets over the tape; the magnets kept sticking to the tape

  • Using wax (candle wax) was even more difficult. I found that I need to heat the wax and press each magnet into warmed wax, which was tedious. But again this did work.

After trying both theses methods I thought of another material that I could use:

  • Adhesive tack (blu tack) turned out to be much easier to use as it could be squeezed around the magnets to collect the silt particles.

tape with several blotches of silt, wax with patches of silt, blue tac uniformly darkened with silt, ring of clean spherical magnets, watch glass with larger particles in background

I think the reason that I didn't think of any of theses options before asking this question was because I was overestimating the strength of the force that the magnet was exerting on the ferromagnetic particles, and underestimating the force of adhesives.

Unfortunately, I still haven't found a way to remove the ferromagnetic silt from the tape, wax, or tack. But this isn't all that that important. I am so glad that my magnets are now clean.

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