Brass

Brass is an alloy composed primarily of copper and zinc, with proportions adjusted to produce a wide range of colours and physical, mechanical, electrical, and acoustic properties. In most formulations, copper is the major component, while zinc is added to modify hardness, strength, and appearance. Brass has been used since prehistoric times and is classed as a substitutional alloy, meaning that atoms of one metal may replace those of the other within a shared crystal structure. It bears close resemblance to bronze, another copper alloy that uses tin rather than zinc. Because historical terminology was often inconsistent, museums and metallurgists increasingly apply the broader category of copper alloys when describing artefacts.
Brass has remained popular for decorative and practical purposes owing to its bright gold-like lustre, durability, corrosion resistance, machinability, and thermal and electrical conductivity. It has long been used in sculpture, utensils, musical instruments, hardware fittings, and engineering components requiring low friction and reliable wear properties.

Composition and Variability

The properties of brass depend strongly on the ratio of copper to zinc. Higher copper content produces softer alloys with a warmer golden appearance, while higher zinc content yields harder, more silvery-coloured materials. Minor additions of other elements can significantly alter brass properties:

• Aluminium increases strength and corrosion resistance, promoting the formation of a thin, protective, self-healing aluminium oxide layer.
• Tin improves resistance to dezincification, making naval brasses suitable for marine environments.
• Iron, silicon, or manganese increase hardness and wear resistance.
• Lead is commonly added (around 2 per cent) to improve machinability, but tends to segregate along grain boundaries, influencing leaching behaviour.

Small amounts of arsenic, phosphorus, and other elements are also used to refine mechanical or anti-corrosion characteristics.
Because brass is non-ferrous, it is easily separated from ferrous scrap using magnets. Nearly 90 per cent of commercial brass is recycled, melted into billets and then extruded or cast into new shapes.

Physical and Mechanical Properties

Brass is valued for its relatively low melting point and excellent flow during casting, making it easy to form complex shapes. The alloy is more malleable than either bronze or zinc, and can often be machined without cutting fluid. Its properties range from soft and ductile to hard and strong, depending on composition.
Despite copper and zinc having widely differing electrical potentials, brass does not suffer internal galvanic corrosion because it contains no internal electrolyte. However, contact with more noble metals such as silver or gold in the presence of moisture may cause the brass to corrode galvanically. Conversely, when brass contacts less noble metals such as zinc or iron, the latter corrode preferentially, protecting the brass.
Exposure to moisture, chlorides, ammonia, acetates, and certain acids can cause surface reactions. Copper within the alloy may react with sulphur to form copper sulphide, which darkens and can later oxidise to a green-blue copper carbonate patina. Depending on conditions, this patina may be protective.

Dezincification-Resistant and Special Brasses

In harsh environments, some brasses undergo selective leaching (dezincification), where zinc is preferentially removed, leaving a porous copper layer. To counteract this, dezincification-resistant (DZR) brasses are used, especially in hot-water or chlorinated systems. These alloys typically include small additions of arsenic and controlled amounts of lead.
Examples include:

• C352 brass containing around 30 per cent zinc, 61–63 per cent copper, 17–28 per cent lead, and trace arsenic.
• Red brasses, a family of alloys with more than 85 per cent copper and less than 15 per cent zinc, often with added tin and lead for improved casting and machining qualities.
• Gunmetal, a red-brass-type alloy with roughly 88 per cent copper, 8–10 per cent tin, and 2–4 per cent zinc.
• Naval brass, containing about 40 per cent zinc and 1 per cent tin, designed for seawater use thanks to its enhanced resistance to zinc depletion.

Regulatory standards increasingly restrict lead content in plumbing and potable-water applications. In California, for instance, maximum allowable lead content for brass components in contact with drinking water has been reduced to 0.25 per cent.

Applications

Brass is widely used for both aesthetic and functional purposes. Common applications include:

• Decorative hardware: drawer pulls, door handles, fittings.
• Engineering components: padlocks, hinges, gears, bearings, hose couplings, valves, zippers, ammunition casings, and plumbing parts.
• Electrical systems: AC power plugs and sockets, connectors, and terminals.
• Jewellery: costume jewellery and fashion accessories, owing to corrosion resistance and gold-like colour.
• Precision settings: environments requiring spark-resistant tools, such as near flammable materials.

Marine use of conventional brass is limited because zinc can react with saltwater minerals, but tin-containing naval brasses and bronzes overcome this limitation.

Use in Musical Instruments

Brass possesses a unique combination of ductility, formability, and acoustic resonance that makes it the preferred material for many wind instruments. It enables long, narrow tubes to be shaped, folded, or coiled without losing structural integrity.
Instruments typically made of brass include:

• trumpet, cornet, flugelhorn
• trombone
• tuba, baritone horn, euphonium
• tenor horn and French horn
• various families such as the saxhorns

Other metal wind instruments, such as student-model flutes, piccolos, and some clarinets, may also be made of brass or cupronickel alloys when traditional dense hardwoods are unavailable. Certain low clarinets, bassoons, and contrabassoons combine wooden body sections with brass or metal tubing for durability and acoustic refinement.
Brass’s acoustic characteristics, coupled with its manufacturability and cost-effectiveness, have ensured its central place in musical instrument production for centuries.