Comparisons · Aluminium and other materials
Aluminium vs steel: which is better?
Weight, strength, stiffness, corrosion and recycling of aluminium and steel, side by side.
In a nutshell
- Aluminium weighs 66% less than steel: 2.70 against 7.85 g/cm³.
- Steel is stronger: 420 against 240 MPa tensile strength.
- Steel is 3 times stiffer (modulus of 205 against 69 GPa): an aluminium profile needs more section to deflect the same amount.
- Aluminium does not rust like steel: it forms an oxide layer that protects it, whereas steel needs paint or galvanising.
| Property | Aluminium 6063-T6 | SAE 1020 carbon steel |
|---|---|---|
| Density | 2.70 g/cm³ | 7.85 g/cm³ |
| Tensile strength | 240 MPa | 420 MPa |
| Modulus of elasticity (stiffness) | 69 GPa | 205 GPa |
| Thermal conductivity | 200 W/m·K | 52 W/m·K |
| Thermal expansion | 23.4 µm/m·°C | 11.7 µm/m·°C |
| Melting point | 615–655 °C | ≈ 1,500 °C |
| Corrosion | Very good: it forms a protective oxide layer; with anodising or paint, excellent. | Low: it rusts and needs paint or galvanising. |
| Machinability | Good | Good |
| Recycling | It can be recycled endlessly using about 5% of the energy needed to produce it. | Recyclable. |
Typical values at room temperature: Aluminium 6063-T6 and SAE 1020 carbon steel. Stiffness compares the modulus of elasticity.
- When aluminium is the better choiceWhen weight, corrosion or finish matter: light structures, windows and doors, transport, visible parts and anything that moves or is assembled by hand.
- When steel is the better choiceWhen you need the highest strength or stiffness in a small section.
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Frequently asked questions
How much does aluminium weigh compared with steel?
Aluminium weighs 66% less than steel: 2.70 against 7.85 g/cm³.
Which is stronger, aluminium or steel?
Steel is stronger: 420 against 240 MPa tensile strength. Steel is 3 times stiffer (modulus of 205 against 69 GPa): an aluminium profile needs more section to deflect the same amount.