Brass is a metal composed primarily of copper and zinc. Copper is the main component, and brass is usually classified as a copper alloy. The color of brass varies from a dark reddish brown to a light silvery yellow depending on the amount of zinc present; the more zinc, the lighter the color. Brass is stronger and harder than copper, but not as strong or hard as steel. It is easy to form into various shapes, a good conductor of heat, and generally resistant to corrosion from salt water. 

Because of its unique combinations of properties brass is generally considered the best material from which to manufacture many components. For example, good strength and ductility are combined with excellent corrosion resistance and superb machinability. Brasses set the standard by which the machinability of other materials is judged and are also available in a very wide variety of product forms and sizes to allow minimum machining to finished dimensions.

Strength

In the softened or annealed condition, the brasses are ductile and strong but when hardened by cold working processes such as rolling or drawing, their strength increases markedly. Strong, stiff structures can be assembled from extruded-and-drawn sections. Bars and rolled sheet and plate can be fabricated into containers and other items of equipment which work under pressure. The strength of brasses is substantially retained at temperatures up to around 200ºC and reduces by only about 30% at 300ºC, which compares favorably with many alternative materials, and easily exceeds the properties of plastics. The brasses are very suitable for use at cryogenic temperatures since the properties, especially strength and toughness, are retained or slightly improved under these conditions.

For applications demanding higher strengths, the "high strength brasses" are available. These contain additional alloying elements such as manganese, which further improve the properties. Some high strength brasses attain strengths that are comparable with steels.

Machinability

While all brasses are intrinsically easy to machine, the addition of small amounts of lead to brasses further improves this property and the well-known "free cutting brass" (UNS Alloy C36000) is universally accepted as setting the standard by which other materials are judged when machinability is being assessed. Higher machining speeds and lower rates of tool wear mean that overall production costs are minimised, tolerances are held during long production runs and surface finish is excellent

Corrosion Resistance

Brasses have excellent resistance to corrosion that makes them a natural, economic first choice for many applications. Atmospheric exposure of the brasses results in the development of a superficial tarnish film. Outdoor exposure will ultimately result in the formation of a thin protective green "patina" which is frequently seen as a visually attractive feature in buildings, but the brass will remain essentially unaffected for an unlimited period of time, i.e. it will not rust away like iron and steel.

Seawater can be handled successfully providing the correct alloy is chosen, and there is a long history of the use of brass tube and tube fittings, valves, etc. in domestic plumbing, central heating, seawater lines, steam condensers and desalination equipment. High strength brasses containing manganese have particularly excellent resistance to atmospheric corrosion, continual exposure resulting in a gradual darkening of the bronze color.