Aluminium or stainless steel: which suits your part?
Neither rusts, and both look good without a coating. Aluminium weighs a third as much and costs less; stainless steel is stiffer, harder and tougher. Which difference matters depends on what the part is for. Here we compare our aluminium AlMg3 with stainless steel 1.4301.
Side by side
| Aluminium AlMg3 | Stainless steel 1.4301 | |
|---|---|---|
| Density | 2.67 g/cm³ | 7.9 g/cm³ |
| Tensile strength | 190 to 250 N/mm² | 540 to 700 N/mm² |
| Elastic modulus (stiffness) | 70 GPa | 200 GPa |
| Thermal conductivity | 130 W/(m·K) | 15 W/(m·K) |
| Rusts | no, seawater resistant | no, pits under salt |
| Magnetic | no | not as delivered |
| Thicknesses with us | 1 to 4 mm | 1 to 5 mm |
Weight and stiffness
At the same thickness an aluminium part weighs a third of the stainless one. Under the same load, though, it deflects almost three times as far, because its elastic modulus is only a third as high.
For an aluminium part to be just as stiff, it has to be about 1.4 times as thick: 3 mm aluminium instead of 2 mm stainless. It then still weighs only half as much. Where weight matters, aluminium is almost always the better choice.
Price
At the same thickness, a part in aluminium costs less with us than in stainless steel, at every quantity. That comes from the weight and from aluminium cutting faster. Even one thickness up it usually stays cheaper. Prices for typical parts are on the aluminium and stainless steel pages.
Surface and working it
Stainless steel is hard and barely scratches. Aluminium is soft: scratches and dents happen more easily, but it can be drilled, sawn and bent with ordinary tools. Stainless needs sharp cobalt drills and work-hardens when a blunt drill rubs.
Aluminium conducts heat almost nine times as well. For parts that have to carry heat away, for example on electronics or LEDs, that is an advantage.
Outdoors and near water
Both last outdoors without a coating. AlMg3 is even seawater resistant. Stainless steel 1.4301 pits under salt, so by the sea aluminium or stainless steel 1.4404 is the better choice. More on that in the 1.4301 and 1.4404 comparison.
Important if you combine the two: aluminium bolted directly to stainless steel corrodes at the contact point as soon as it gets wet. A plastic washer in between prevents that.
Our recommendation
It has to be light: robotics, drones, models, anything portable
Front panels and enclosures for electronics
Aluminium. Easy to work, carries heat away and costs less.
House numbers, signs and parts that get handled a lot
Stainless steel. Hard, scratch resistant and still good-looking after years.
Kitchen, food, hygiene
Brackets that carry something, in thin sheet
Stainless steel. Aluminium sags under load over time. If it does not have to be rustproof, S355MC steel costs less.
By the sea, on a boat
Aluminium AlMg3, or stainless steel 1.4404 on request.
You see the price for every material before you order.