Aluminium vs Steel
Aluminium and Steel are genuine alternatives to one another — a choice somebody actually makes — and differ on 5 measured properties, density most clearly.
Aluminium vs Steel
These are different kinds of thing (element, alloy). Fewer properties mean the same thing across both, so a like-for-like reading may not be available.
Aluminium
Al
The most abundant metal in the Earth's crust, and until the 1880s more valuable than gold because nobody could extract it cheaply.
Steel
Iron with a controlled, small proportion of carbon — the most-used engineered material in the world.
| Property | Aluminium | Steel |
|---|---|---|
| Atomic number Only one of the two has a figure we can stand behind, so there is nothing to compare. | 13 | Not known |
| Density | 2.7 g/cm³ | 7.75–8.05 g/cm³ higher |
| Electrical conductivity | 37.7 MS/m higher | 6.99 MS/m |
| Melting point | 660.32 °C | 1370–1510 °C higher |
| Mohs hardness Only one of the two has a figure we can stand behind, so there is nothing to compare. | about 2.75 | Not known |
| Molar mass Only one of the two has a figure we can stand behind, so there is nothing to compare. | 26.982 g/mol | Not known |
| Tensile strength | 70–130 MPa | 400–2000 MPa higher |
| Thermal conductivity | 237 W/(m·K) higher | 15–54 W/(m·K) |
Choosing between them
Aluminium is recorded as a substitute for Steel — lighter, more corrosion-resistant.
What it gives up: A third the stiffness for the same section, so an aluminium structure must be deeper or thicker to match a steel one — and it costs several times more per tonne.
In this application, on the evidence cited above.