Brass

Brass is an alloy of copper and zinc, in proportions which can be varied to achieve varying mechanical, electrical, and chemical properties. It is a substitutional alloy: atoms of the two constituents may replace each other within the same crystal structure.

Brass is similar to bronze, another alloy containing copper that uses tin instead of zinc. Both bronze and brass also may include small proportions of a range of other elements including arsenic, lead, phosphorus, aluminum, manganese, and silicon. Historically, the distinction between the two alloys has been less consistent and clear, and modern practice in museums and archaeology increasingly avoids both terms for historical objects in favor of the more general "copper alloy".

Brass has long been a popular material for decoration due to its bright, gold-like appearance; being used for drawer pulls and doorknobs. It has also been widely used to make utensils due to properties such as having a low melting point, high workability (both with hand tools and with modern turning and milling machines), durability, and electrical and thermal conductivity.

Brass is still commonly used in applications where corrosion resistance and low friction are required, such as locks, hinges, gears, bearings, ammunitioncasings, zippers, plumbing, hose couplings, valves, and electrical plugs and sockets. It is used extensively for musical instruments such as horns and bells, and also used as a substitute for copper in making costume jewelry, fashion jewelry, and other imitation jewelry. The composition of brass, generally 66% copper and 34% zinc, makes it a favorable substitute for copper based jewelry, as it exhibits greater resistance to corrosion. Brass is not suitable for such items as boat propellers because the zinc reacts with minerals in salt water, leaving porous copper behind. The tin in bronze will not react with these minerals.

Brass is often used in situations in which it is important that sparks not be struck, such as in fittings and tools used near flammable or explosive materials.