Magnet Maintenance

While storing, keep them attached, N-S-N-S-... and short the ends. Or put a shorting iron ipece like this (fig 14 and the para above it)

The like expectancy depends on the material properties, usage, temperature etc.

These anyway can be re-magnetised easily.

Our material handling systems (or even as simple as the dial gauge stands) are with permanent magnet bases but now even after some 20-25 years the strength has not gone down at least effectively (not measured with gauss meter but are still effectively doing there function)

You should really not ask such controversial questions.

I'll start the ball rolling by saying that they will get weaker, no matter how you store them. But not quickly. How would you know, anyway?

Don't expose them to an electromagnetic field and withdraw them from the field or the will be "degaussed". Check out how to gauss a magnet.

Naturally occurring magnets are called lodestone.

Just stick them somewhere and don't worry about them.

Cheers!

The iron piece bridging across the magnet's pole, as Guest describes, is traditionally called a "keeper" because it preserves the strength of the magnet.

You do not have to worry,magnet will not loose power over time. just do not expose to high temperature. If you keep them together stuck after while (longer time period) magnet's will be harder to separate.

If they're NeFeB magnets, they have probably been "knocked down" to a stable level, and same for Samarium Cobalt magnets. NeFeB magnets will rust and stick together, and they're indeed harder to separate then than before, which is why most I have purchased are nickel-plated.

P. S. Don't you think it's a little rude to call people who may be kind enough to respond to your post, "Phorum Phreaks?"

Bill,

Thanks for the response about magnets.

I suppose some people feel threatened about other peoples humor. I apologize if I've offended you personally.....

As for me, I'm definitely a 'phorum phreak' (thats 'forum freak' for all the spelling police out there) as I'm a member of 10 different forums so far. Maybe I should have changed it to Phorum Phinatics? Or....Phorum Phrends? On the ATCA (Antique Telephone Collectors Association) forum, all 800 +/- members have picked up the phorum phreak phrase and use it regularly. All in jest.

Ron (Old Telephone Nut)

Actually, there was no offense taken, and I posted without putting a 'smiley face' next to my post script, but that's 'cause I was suffering from a "senior moment" at the time.

By the way, Oregon is probably a good place for magnets to rust together -- even AlNiCo's.

I bought a couple of NeFeB donut magnets several years ago, and I stuck them on the refrigerator with about 1 1/2" wood between each of the magnets and the refrigerator. My son and daughter came for Thanksgiving dinner 3-4 years ago, and Matt asked, "Why do you have so much wood between the magnets and the frige?" I said, "So I can get them loose -- watch this!," as I pulled one away while catching the wood with my free hand. Before I knew it, the refrigerator door flew open and caught the end of my finger between two of the awfullest magnets I have ever owned and pinched off a chunk of the fingerprint on my right middle finger! It took Matt and me about fifteen minutes to separate the magnets with a vise and a couple of pieces of wood, and when we did, the missing flesh fell to the floor. Unnoticed by me, he left it behind in a small plastic bag, stuck to the frige with a note that read, "When smart people do stupid things . . ."

Bill (Just plain ol' nut)

look up coercivity and remanence

http://hyperphysics.phy-astr.gsu.edu/hbase/solids/magperm.html

Magnets are best stored so that the magnetic circuit is "closed". For example, a "U" shaped magnet will last the best if it has a steel bar placed across the ends of the "U". By the same token, if your magnets are stuck together, they will tend to keep each other magnetized, but they might also benefit if they are stuck to a piece of steel as well.

They should las a lifetime if they aren't heated, banged around, or stored so their magnetic fields oppose each other.

Depending on the material and geometry of your magnets, they will typically loose less than 5-10% of their full saturated field strength over life and normal use [applying and removing, +/- 40°F fluctuations and no exposure to alternating (degaussing) or opposing fields equal or greater than their magnetic field srtength]. You can even minimize this loss by following some of the good storage suggestions in this thread.

There's been lots of good information here. Thank you all. Now I'm worried about them rusting because the application I'm using them in requires them to be outdoors in rainy weather. Would it hurt them if I painted them with some sort of rust proof paint?

Thanks, Ron

Paint won't hurt them at all. I suggest Rustoleum.

Rustoleum works great on the outer surfaces, but in order to reduce the gap between the magnetic face and the metal plate, you might want to use some thin oil. That is if you don't mind dusty oily stains on your stuff .

Yahlasit

Do you mean to not paint the contact surface? How much magnetic loss would occur if I do paint it? Thanks, Ron

Almost unnoticable change in magnetic strength due to paint.

The only thing you really need to worry about is the temperature. You do not want to have the temperature > 0.4 * (Currie Temperature for the magnet).

All other storage issues are within the noise, unless you are holding them in a strong magnetic field.

If you are using Nb based magnets then store them N-S-N-S in a stack.

Huh? What the heck is Currie Temp? Noise? What noise? Please tell me what Currie temp. is in Fahrenheit....Thanks, Ron

Curie temperature is the point at which crystalline grains of the material are free to move about, and it is also the point at which they can be subjected to a high magnetic field and be cause to align themselves with it, to put it in simple terms.

I think 'Guest' used "noise" as a general term to indicate that not much will affect magnetic strength, but I could be wrong. Acoustic noise won't hurt magnets before it kills any human in the neighborhood.