Is aluminium magnetic? How to tell aluminium from steel, and what it is worth
Aluminium is not magnetic. A magnet will not stick to it, which is the quickest way to pick it out of a pile of steel, and the sorting is worth doing: aluminium is paid at several times the rate for steel at a UK scrap yard.
Aluminium and magnets: key facts
| Is aluminium magnetic | No. A hand magnet will not stick to pure aluminium or to any common aluminium alloy |
|---|---|
| Why not | Aluminium is paramagnetic: it responds to a magnetic field so weakly that you cannot feel it |
| What a magnet does do to it | Sets up eddy currents. A magnet dropped down an aluminium tube falls slowly, and recycling plants use the same effect to sort it |
| Weight | About 2.7 grams per cubic centimetre, roughly a third of steel |
| When a magnet does stick | There is steel in it: screws, rivets, a steel core in overhead cable, or the item is plated steel |
| Why it matters | Clean aluminium is worth several times more than steel by weight, and a mixed load is paid at the cheaper rate |
Why a magnet will not stick to aluminium
Ferromagnetism, the kind of magnetism you can feel, needs a metal whose atoms line up their magnetic moments together. Iron, nickel and cobalt do that. Aluminium does not. It is paramagnetic, meaning it is drawn to a magnet so faintly that no hand magnet and no scale in a scrap yard will register it. For every practical purpose, aluminium is not magnetic, and neither is any of the alloys you are likely to meet, from drinks cans to window frames to engine parts.
Aluminium does react to a moving magnet in a different way. Because it conducts electricity well, a changing magnetic field sets up circulating currents inside it, called eddy currents, and those currents push back against the magnet. Drop a strong magnet down a length of aluminium tube and it drifts down slowly instead of falling. Recycling plants rely on exactly this: after an overband magnet has lifted the steel out of a shredded stream, an eddy current separator throws the aluminium off the end of a conveyor while glass, plastic and stone fall straight down.
Telling aluminium from the metals it gets confused with
Steel. The magnet settles it. Steel sticks, aluminium does not. Painted or galvanised steel can look like aluminium once it has weathered, so test rather than trust the colour.
Stainless steel. The common 300 series grades are not magnetic either, so the magnet test alone cannot tell polished aluminium from polished stainless. Weight can: a stainless item is close to three times as heavy as the same item in aluminium. A scratch helps too. Aluminium scratches easily with a key or a knife point and leaves a soft, bright grey line; stainless resists. Our guide to whether stainless steel is magnetic covers the grades that do and do not stick.
Zinc die castings. Door handles, carburettor bodies, toys and trim are often zinc alloy, which is not magnetic and takes a silvery finish. Zinc is heavy, about seven grams per cubic centimetre, so a zinc casting feels more like steel in the hand than aluminium. It is also brittle and snaps rather than bending.
Magnesium. Rarer, lighter still, and found in some wheels, casings and older vehicle parts. It is not magnetic. A yard identifies it with a handheld analyser or a spark test, so if a very light casting is not obviously aluminium, let them grade it.
Copper and brass. Also non magnetic, but the colour gives them away. Where aluminium and copper meet is in cable: aluminium conductor is common in overhead and some underground power cable, and the steel reinforced kind will grab a magnet because of its steel core, not its aluminium.
Where aluminium turns up
Drinks cans, foil and food trays. Window and door frames, curtain walling and conservatory sections, usually extruded and often with steel fixings, rubber seals and glass still attached. Car and van parts: wheels, cylinder heads, gearbox casings, radiators and heat exchangers. Ladders, scaffold boards and signage. Litho printing plates. Electrical cable and busbar. Each of these is a recognised scrap grade with its own price, and the clean, sorted grades pay best. Our guide to aluminium grades for scrap explains what the yard means by extrusion, cast, wheels, cans and irony aluminium.
What aluminium is worth
Aluminium is one of the most valuable common scrap metals after copper and brass, and the gap to steel is wide. This month's figures are on our aluminium scrap price page, with the scrap metal prices page carrying the other metals. Two rules decide what you are actually paid. Clean aluminium, free of steel, plastic and rubber, earns the full grade price; aluminium with steel still attached is bought as irony aluminium at a fraction of it. And a mixed load is priced close to its cheapest component, so a few minutes with a magnet and a screwdriver before you weigh in is the best paid work you will do that day.
- Pull the magnet over everything. Anything that sticks goes in the steel pile.
- Take the steel out of the aluminium. Screws, hinges, brackets and the steel core of cable. If it cannot come out, it goes in as irony aluminium.
- Keep the grades apart. Cans, extrusions, cast, wheels and cable are paid at different rates. Mixing them earns the lowest.
- Weigh the doubtful ones. Light and non magnetic is aluminium or magnesium. Heavy and non magnetic is stainless or zinc.
For more than a car boot load, having it collected usually beats driving it in. Our guide to scrap metal collection explains who collects and what it changes about the price, and the directory below lists the yards and collectors in your postcode area.
Frequently asked questions
Is aluminium magnetic?
No. Aluminium is paramagnetic, which means it is attracted to a magnet so weakly that you cannot feel it. A hand magnet will not stick to aluminium or to any common aluminium alloy.
Why does a magnet stick to my aluminium window frame?
It is sticking to steel, not aluminium: fixing screws, a steel reinforcing bar inside the section, or steel hinges and brackets. Take the steel out and the aluminium will not hold a magnet.
How can I tell aluminium from stainless steel?
Weight and a scratch. Stainless is nearly three times as heavy as aluminium for the same size, and aluminium scratches easily with a key while stainless resists. Common stainless grades are not magnetic either, so the magnet alone does not settle it.
Why does a magnet fall slowly through an aluminium tube?
Because the moving magnet induces eddy currents in the aluminium, and those currents create their own magnetic field that pushes back. Recycling plants use the same effect, in eddy current separators, to flick aluminium out of a mixed stream.
Is aluminium worth more than steel as scrap?
Yes, by a wide margin per kilogram. That is why sorting aluminium out of steel with a magnet before you weigh in is worth doing: a mixed load is paid at close to the rate for its cheapest part.