Gunmetal

Alloys of copper with tin, zinc and lead have been used for at least 2000 years due to their ease of casting and good strength and corrosion resistance. Early uses were for brooches, mirror cases, church doors, fonts and statues. The use for cannons in Mediaeval times led to the term 'gun metal' being adopted; this use is now obsolete with the manufacture of steel ordnance.

Today, in the UK, the term 'gunmetal' is applied to a family of copper-based casting alloys containing between 2-11% tin and 1-10% zinc. Modified forms may contain, in addition, such elements as lead (up to 7%) and nickel (up to 6%) when the alloys are classified as 'leaded gunmetal' and 'nickel gunmetal'.

Gunmetals are noted for the manufacture of intricate castings required to be pressure tight such as valves, pipe fittings and pumps.

They are also frequently used for bearings where loads and speeds are moderate.

Gunmetals are the first choice for modern statues; recent examples being:

• Bobby Moore (outside Wembley Stadium)
• Nelson Mandela (in Parliament Square)
• 'The Meeting Place' (in St. Pancras International Station, London).

Publications

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Pub 42 Copper and Copper Alloy Castings
Discusses the various applications of all copper casting alloys commonly available in Europe with recommendations as to the choice of alloy. Casting processes are described and product design considerations which apply to castings are considered. 1991. 62pp.

Pub 44 Machining Brass, Copper and Copper Alloys
Detailed advice on machining techniques. Guide to choice of speeds and feeds. Comprehensive list of British and European alloys with details of machinability. Advice on the selection of cutting fluids. 1992. 84pp.

Pub 45 Copper Alloy Bearings
Covers the British and European alloys which are suitable for bearing applications, giving advice on their selection and use. 1992. 44pp.

Pub 97 Design for Production
Describes the production processes used to produce components from coppers and copper alloys listing the advantages of each. An invaluable reference book for design engineers. 1994. 90pp.

Pub 106 Corrosion Resistance of Copper and Copper Alloys
This large table gives information on the suitability of copper and copper alloys with many different chemicals. Data is given for copper, brass, copper-nickel, aluminium bronze and gunmetals at three temperatures: 20^oC, 60^oC and 100^oC . The table shows when specific materials can and cannot be used with the chemicals giving an indication of corrosion resistance. 5pp.

Other Reference Material

Gunmetal Castings
by Frank and D A Hudson Macdonald Technical, 1967.