Goudsmit Magnetics says a magnet mainly attracts materials containing iron, nickel or cobalt, such as steel and cast iron. K&J Magnetics says aluminum and copper aren’t ferromagnetic, so magnets won’t stick to them, and Goudsmit adds brass, bronze, gold, silver, lead, zinc, tin and titanium. Stainless steel depends on the grade.
Metals a magnet sticks to, and metals it won’t
| Metal | Does a magnet stick? | Who says so |
|---|---|---|
| Iron | Yes | K&J and Goudsmit |
| Steel and cast iron | Yes | K&J: “Steel is ferromagnetic because it is an alloy of iron and other metals”; Goudsmit |
| Nickel and cobalt | Yes | K&J and Goudsmit |
| Stainless steel | Ferritic and martensitic grades, yes; austenitic grades such as 304 and 316, usually not | SSINA and Goudsmit |
| Aluminum | No | K&J and Goudsmit |
| Copper | No | K&J and Goudsmit |
| Brass and bronze | No | Goudsmit |
| Gold and silver | No | Goudsmit |
| Lead, zinc, tin and titanium | No | Goudsmit |
Goudsmit says the metals marked no may respond very weakly to a magnetic field, but not in a way you’d notice with a standard magnet. It also lists “certain magnetic alloys” among what a magnet attracts, without naming them.
Why some metals hold a magnet and others don’t
K&J says magnets strongly attract ferromagnetic materials, and that iron, nickel and cobalt are the most commonly available ones. Its plain-English definition of ferromagnetic is “Stuff that magnets stick to”, with refrigerator doors among its examples. Goudsmit puts it another way: “metal” is not the same as “magnetic”.
Aluminum and copper still react to a magnet that moves. K&J says a changing magnetic field induces eddy currents in them. Its video of the classic demonstration drops a magnet down a copper or aluminum tube, and it says eddy current separators use the effect to separate aluminum cans from trash. Goudsmit says the same: a magnet doesn’t hold these metals, but a changing field can make them move.
A few materials push back. K&J calls them diamagnetic and names bismuth and pyrolytic carbon, plus water, only slightly. It says even the strongest of these repel with a very small force.
Stainless steel depends on the grade
SSINA says ferritic, martensitic and duplex stainless grades are magnetic, and austenitic grades such as 304 and 316 are not when annealed. K&J’s FAQ says stainless can vary much more wildly than plain steel, and some grades aren’t ferromagnetic at all. For the grade-by-grade detail and the fridge question, see do magnets stick to stainless steel.
Using a magnet to sort metal
Goudsmit says a magnet test is useful as a first indication but isn’t always enough to tell exactly what a metal is. We’d treat it that way: if a magnet won’t stick, we wouldn’t assume we knew which metal we had.
Handling strong magnets safely
- Pinching: K&J says fingers can be pinched between two neodymium magnets, and with larger magnets the injury can be severe.
- Shattering: it says they can chip, crack or shatter if they slam together, and that eye protection should be worn.
- Implants: it says the strong fields near a neodymium magnet can affect pacemakers, ICDs and other implanted medical devices. Its FAQ says to ask a physician or the device’s maker about a safe distance.
- Nickel allergy: it says people with a nickel allergy should avoid handling nickel-plated magnets directly.
- Cards: its FAQ says strong magnets can damage credit cards, magnetic ID cards and other magnetic media.
K&J Magnetics, which sells neodymium magnets, says they are not toys and that if several are swallowed they can attach to one another through the intestine walls. The CPSC says that if you suspect magnets have been swallowed, seek immediate medical attention. We’d keep small strong magnets away from children. The CPSC lists abdominal pain, nausea, vomiting and diarrhea as symptoms to watch for.
Magnet won’t stick to your stainless fridge?
Magnets on stainless steel