Iron

Chemically pure iron is barely used — it is soft, and it rusts faster than the steels made from it. Adding 0.2% carbon roughly doubles its strength, which is the entire basis of the steel industry. Its stiffness of 211 GPa is essentially unchanged by alloying, so every steel from a coat hanger to a submarine hull has the same Young's modulus: heat treatment changes strength, never stiffness.

Properties

Density

7,874 kg/m³ — 7.87 g/cm³

Melting point

1,538 °C

Tensile strength

200–350 MPa

Young's modulus

211 GPa

Thermal conductivity

80.4 W/(m·K)

Thermal expansion

11.8 µm/(m·K)

Floats in water

No

Magnetic

Yes

What it is used for

• Feedstock for all steelmaking
• Transformer and motor cores (as electrical iron)
• Magnetic shielding
• Laboratory and reference standards

How it compares

Does it rust?

Yes, and readily. Rust is iron oxide, and it is flaky rather than adherent — it does not seal the surface, so oxygen and water keep reaching fresh metal underneath and the process continues until the section is gone. That non-protective quality is what makes rust different from the oxide layers on other metals.

Is it magnetic?

Iron, nickel and cobalt are the three common ferromagnetic elements, and anything based mostly on them is strongly attracted to a magnet.