Bronze

Copper and tin rather than copper and zinc, and the difference shows up as bearing behaviour: bronze runs against steel without galling, which is why bushings are bronze and not brass. Phosphor bronze adds a fraction of a percent of phosphorus and becomes a spring material that resists fatigue better than brass. Bell bronze runs to 20% tin, which makes it hard and brittle and gives it the long ring; the same composition would be useless as a bearing.

Properties

Density

8,800 kg/m³ (8,700–8,900) — 8.80 g/cm³

Melting range

950–1050 °C

Tensile strength

350–700 MPa

Young's modulus

110 GPa

Thermal conductivity

62 W/(m·K)

Thermal expansion

18 µm/(m·K)

Floats in water

No

Magnetic

No

What it is used for

• Plain bearings and bushings
• Ship propellers and marine fittings
• Statues and bells
• Springs and electrical contacts (phosphor bronze)

How it compares

Does it rust?

No. Copper and its alloys cannot rust, since rust is iron oxide. They form a patina instead — copper oxide first, turning to the familiar green carbonate over decades — and that layer is adherent and protective, which is why copper roofs last centuries.

Is it magnetic?

Bronze is not ferromagnetic. It is often assumed to be because it is a metal, but most metals are not — only iron, nickel, cobalt and a few alloys are attracted to an ordinary magnet.