Is copper magnetic? The magnet test and what it misses
Copper is not magnetic. A magnet will not stick to it, which is the quickest way to tell copper from the steel it is often mixed with. The test is genuinely useful, and it is also wrong more often than people expect.
The magnet test: key facts
| Is copper magnetic | No. Copper is not ferromagnetic, so a hand magnet will not stick to it |
|---|---|
| What a magnet separates | Ferrous metals, meaning iron and steel, from everything else |
| Ferrous, so magnetic | Mild steel, cast iron, most 400 series stainless |
| Non ferrous, so not magnetic | Copper, brass, aluminium, lead, zinc, nickel, 300 series stainless |
| Which is worth more | Non ferrous, usually by a wide margin |
| What a magnet cannot do | Tell you which non ferrous metal you have, or which stainless grade |
Why the test works
Iron's atomic structure lets its magnetic moments line up, which is what ferromagnetism is. Copper's does not. In an industrial plant this is the very first sorting stage: an overband magnet lifts the ferrous fraction out of a mixed stream, and the non ferrous metals that stay behind are then separated by eddy current, which works on electrical conductivity rather than magnetism.
At the kerbside or in a van, the same physics gives you a free sorting tool. Ferrous metal is the cheapest material in the yard by weight. Non ferrous is where the money is. Pulling a magnet over a load before you weigh it in is the single cheapest thing you can do to improve what you are paid, because a mixed load is priced close to the rate for its cheapest component.
The first thing the test gets wrong: plated steel
A copper coloured item that a magnet sticks to is not copper. It is copper plated or copper flashed steel, and there is a great deal of it about: decorative fittings, some cable glands, hardware, kitchenware. The magnet is telling you the truth and the colour is lying.
This cuts the other way too. A non magnetic item is not necessarily copper. Brass, bronze and some aluminium alloys sit in the same colour range once they have oxidised. Weight and sound help: copper is dense and dull when struck, aluminium is noticeably light.
The second thing it gets wrong: stainless steel
Stainless is where a magnet test quietly falls apart. Ferritic and martensitic stainless, including most of the 400 series, are magnetic. Austenitic grades such as 304 and 316 are practically non magnetic, with magnetic permeability close to that of air. So a magnet can sometimes tell you which family a piece of stainless belongs to, and that is all.
Worse, a 304 that was non magnetic when it left the mill can become slightly magnetic once it has been cold worked, which means bent, pressed or machined. A sink bowl or a formed bracket can read differently from the flat sheet it was cut from. And no magnet will ever distinguish 304 from 316, which is the distinction that matters commercially, because 316 contains molybdenum and 304 does not. Yards use a handheld analyser for that, not a magnet.
How to use it properly
- Sort into two piles first. Sticks, and does not stick. That alone separates the cheap from the valuable.
- Then sort the non magnetic pile by appearance and weight. Copper, brass, aluminium and lead all look and feel different once you have handled a few.
- Treat stainless as its own problem. If it looks like stainless, put it aside and let the yard grade it.
- Check anything copper coloured with the magnet again. Plating is the commonest mistake.
Our copper scrap price and scrap metal prices pages carry the current UK rates, and The Waste Stock Calculator on the directory page converts a weight into a figure at today's pricing.
For anything beyond a car boot load, having it picked up usually beats driving it in, and our guide to scrap metal collection covers when a yard will collect and what it changes about the price.
Frequently asked questions
Is copper magnetic?
No. Copper is not ferromagnetic, so a hand magnet will not stick to it. That is why a magnet is the quickest way to separate copper from the steel it is usually mixed with.
Why does a magnet stick to my copper pipe then?
Because it is almost certainly copper plated or copper flashed steel rather than solid copper. The magnet is right and the colour is misleading.
Is stainless steel magnetic?
It depends on the grade. Ferritic and martensitic stainless, including most 400 series, are magnetic. Austenitic grades such as 304 and 316 are practically non magnetic, though a 304 can become slightly magnetic after being bent or pressed.
Can a magnet tell 304 from 316 stainless?
No. Both are austenitic and practically non magnetic. The difference is molybdenum, which 316 contains and 304 does not, and yards identify it with a handheld analyser.
Which is worth more, ferrous or non ferrous?
Non ferrous, usually by a wide margin. That is why sorting with a magnet before you weigh in is worth doing: a mixed load is paid at close to the rate for its cheapest component.