What is brass?
What is brass?
Brass is a metal alloy of copper and zinc; the proportions of which can be varied to create a range of brasses with varying properties. Brass is typically used for decorative purposes due to its resemblance to gold.
Constituents of brass
Copper is brass’ main ingredient (between 55% and 95%), and brass is often classified as a copper alloy. To enhance its machinability, lead is often added to brass in concentrations of around 2%. Aluminium can be added to make brass stronger and increase its resistance to corrosion. It also causes a hard layer of aluminium oxide (Al2O3) to be formed on the surface that is protective, thin, transparent and self-healing. Tin has a similar effect and is used as an alloy especially in seawater applications (naval brasses).
Colours and comparative strength
Its colour varies from a dark red/brown to a light silver/yellow depending on the amount of zinc added; the more zinc, the lighter the colour. The zinc used to make brass is a commercial grade sometimes known as spelter. Copper is softer, and steel stronger than brass.
Manufacturing and machining
The process used to manufacture brass involves combining the raw materials into a molten metal, which then solidifies. Its relatively low melting point (900 to 940 °C, 1652 to 1724 °F, depending on its composition) and flow characteristics, make brass a relatively easy material to cast. By varying the proportions of zinc and copper, the properties of the brass can be changed, allowing different weights, strengths and colours.
Brass is often the chosen metal where it is imperative that sparks are not struck, for example fittings and tools around explosive gases. Its malleability and acoustic properties have resulted in it being a popular choice for musical instruments.
Brass has been known for its bactericidal properties for centuries and this was confirmed in the laboratory in 1983. Copper in brass makes the brass germicidal. Depending upon the concentration and type of pathogens and the medium they are in, brass kills microorganisms within a few minutes to hours of contact. This makes brass ideal for items such as door knobs, where bacteria can spread. Today, almost 90% of all brass alloys are recycled