What is the difference between gunmetal and brass?

Brass is mainly copper and zinc. Gunmetal is copper with tin, zinc and often lead, which gives better corrosion resistance and pressure tightness for valves and pumps.

Gunmetal or phosphor bronze for bushes?

Phosphor bronze takes higher loads and wear; LG2 gunmetal is cheaper, machines more easily and suits moderate loads, especially where water is present.

Why is gunmetal used for valves?

It casts free of leaks, resists water and steam corrosion, and machines cleanly for seats and threads.

Gunmetal LG2: composition, properties and uses

LG2 is a leaded gunmetal, a copper alloy with about 5% each of tin, zinc and lead. It casts pressure-tight, resists water and seawater corrosion, machines easily and runs well as a bearing. It is the standard material for valves, pump parts, bushes and plumbing fittings.

Quick facts

Type: Leaded tin bronze (gunmetal), cast
Composition: About 85% copper, 5% tin, 5% zinc, 5% lead
Tensile strength: About 200–270 MPa
Hardness: About 60–70 HB
Machinability: Very good (lead)
Close equivalents: CuSn5Zn5Pb5, CC491K, C83600

Equivalent grades

Standard	Grade
BS 1400	LG2
EN 1982	CuSn5Zn5Pb5-C, CC491K
ASTM / UNS	C83600

Equivalents are close, not identical. Name the grade and standard on the drawing.

Typical chemical composition

Element	%
Copper (Cu)	About 84–86
Tin (Sn)	About 4–6
Zinc (Zn)	About 4–6
Lead (Pb)	About 4–6

Values are typical. The exact limits depend on the standard and supplier; ask for the mill test certificate when it matters.

Typical uses

Valve bodies, discs and seats
Pump casings and impellers
Bushes and bearings at moderate loads
Plumbing and marine fittings
Pressure-tight castings

Good to know

Usually sand cast, centrifugally cast or continuously cast as bar
Lead makes it easy to machine and helps bearing performance
For drinking water, check local rules on lead content

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Questions

What is the difference between gunmetal and brass?: Brass is mainly copper and zinc. Gunmetal is copper with tin, zinc and often lead, which gives better corrosion resistance and pressure tightness for valves and pumps.
Gunmetal or phosphor bronze for bushes?: Phosphor bronze takes higher loads and wear; LG2 gunmetal is cheaper, machines more easily and suits moderate loads, especially where water is present.
Why is gunmetal used for valves?: It casts free of leaks, resists water and steam corrosion, and machines cleanly for seats and threads.

The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 15 October 2026.