Aluminum behaves like a non-magnetic metal in every workshop test: a magnet slides off it, it cannot be picked up, and it will not hold a field. The technical answer is that aluminum is paramagnetic - very slightly attracted - which is a different thing from being non-magnetic, and the difference matters when the question comes from an engineer rather than from the shop floor.
Is aluminum magnetic?
No, not in any practical sense. Aluminum is paramagnetic: it is very weakly attracted to a magnetic field, with a relative permeability of about 1.000022, so the attraction is too small to feel and a magnet will never stick to it. All the common alloys - 1050, 3003, 5052, 6061, 6082 - behave the same way, and cold working does not change it. This is why aluminum is used for enclosures around magnetic sensors, for non-magnetic fixtures, and why an eddy-current separator can sort aluminum from plastic even though the metal is not magnetic: that machine works on electrical conductivity, not on magnetism. If a magnet does stick to an aluminum part, there is steel in it - an insert, a fastener, a plating, or mixed swarf on the surface.
Paramagnetic, diamagnetic, ferromagnetic
- Ferromagnetic - strongly attracted, and able to stay magnetised. Iron, steel, nickel, cobalt, and the ferritic stainless grades 430 and 430F. This is what people mean by "magnetic".
- Paramagnetic - weakly attracted, cannot stay magnetised. Aluminum, titanium, and annealed austenitic stainless such as 304.
- Diamagnetic - weakly repelled. Copper, brass, bronze, silver, lead, and water.
- Why the labels matter - a part that must not disturb a magnetic field needs either a diamagnetic or a paramagnetic material. Both aluminum and copper qualify, which is why sensor and instrument housings come in both.
Magnetic response of the metals we would quote
| Material | Type | Relative permeability | Magnet sticks? |
|---|---|---|---|
| Aluminum 1050 / 3003 | Paramagnetic | ≈ 1.00002 | No |
| Aluminum 5052 / 6061 / 6082 | Paramagnetic | ≈ 1.00002 | No |
| Copper C11000 | Diamagnetic | ≈ 0.999994 | No |
| Brass / bronze | Diamagnetic | ≈ 0.99999 | No |
| 304 stainless, annealed | Paramagnetic | ≈ 1.002–1.02 | Very weak or none |
| 304 stainless, heavily cold formed | Paramagnetic + strain martensite | Rises locally with cold work | Weak, sometimes noticeable |
| 430 / 430F stainless | Ferromagnetic | ≈ 500–1,700 | Yes, strongly |
| Pure iron / DT4E | Ferromagnetic | Several thousand | Yes, strongly |
Values are the normal published ranges, shown to give the orders of magnitude. The gap between aluminum at 1.00002 and 430F at several hundred is the whole answer to the question.
Does anodising or coating change it?
No. Anodising converts the surface of the aluminum itself into an oxide layer, and that oxide is not magnetic either, so an anodised part behaves exactly like the bare one. The same is true of powder coating and painting: the film that is added is a polymer or a ceramic, neither of which becomes ferromagnetic. What does change the test result is anything steel in the assembly - a steel insert, a stainless fastener of the 430 family, a plated screw, or steel swarf pressed into the surface by a brush that was used on carbon steel.
Why this is useful rather than academic
- Sensor and instrument housings - a non-magnetic housing does not bend the field around the sensing element, so the reading stays honest. This is the reason copper and aluminum appear on the same bill of materials as 430F and pure iron parts.
- Eddy-current sorting - the same conductivity that makes aluminum useful in a motor also makes it easy to separate in a recycling line, even though the metal is not magnetic.
- Assembly checks - a magnet is the fastest incoming check on a mixed box: it finds steel inserts and mislabelled fittings in a second.
- Fastening and fixtures - aluminum work does not need de-magnetised fixtures, but swarf control matters more, because steel contamination is what turns a non-magnetic part into one that fails the test.
Key point
Aluminum is paramagnetic and effectively non-magnetic; a magnet will not stick, and no finish changes that. If a customer reports that an aluminum part is magnetic, look for a steel insert or contamination before looking at the material certificate.
Frequently asked questions
Is 6061 aluminum magnetic?
No. 6061 is paramagnetic like the other common alloys, with a relative permeability barely above 1, so a magnet does not stick to it.
Why does a magnet stick to my aluminum part?
Because there is iron in it somewhere: a steel insert, a plated or stainless fastener of a ferritic grade, or steel swarf embedded in the surface from a shared brush or machine.
Is anodised aluminum magnetic?
No. Anodising grows an oxide layer from the aluminum itself, and that oxide is non-magnetic, so the part behaves the same as bare aluminum.
Can you sort aluminum with a magnet?
No. Aluminum cannot be separated with a magnet; eddy-current separators sort it by electrical conductivity, which is why they work on aluminum and copper alike.