This often happens when the copper reacts with sulfur to form a brown and eventually black surface layer of copper sulfide which, if regularly exposed to slightly acidic water such as urban rainwater, can then oxidize in air to form a patina of green-blue copper carbonate. Binary phase diagramīrass will corrode in the presence of moisture, chlorides, acetates, ammonia, and certain acids. The addition of as little as 1% iron to a brass alloy will result in an alloy with a noticeable magnetic attraction. Combinations of iron, aluminium, silicon, and manganese make brass wear- and tear-resistant. Tin has a similar effect and finds its use especially in seawater applications (naval brasses).
Aluminium also causes a highly beneficial hard layer of aluminium oxide (Al 2O 3) to be formed on the surface that is thin, transparent, and self-healing. Īluminium makes brass stronger and more corrosion-resistant. The general softness of brass means that it can often be machined without the use of cutting fluid, though there are exceptions to this. Brass scrap is melted and recast into billets that are extruded into the desired form and size. Because brass is not ferromagnetic, ferrous scrap can be separated from it by passing the scrap near a powerful magnet. Today, almost 90% of all brass alloys are recycled. By varying the proportions of copper and zinc, the properties of the brass can be changed, allowing hard and soft brasses. The relatively low melting point of brass (900 to 940 ☌ 1,650 to 1,720 ☏, depending on composition) and its flow characteristics make it a relatively easy material to cast. Properties Microstructure of rolled and annealed brass (400× magnification)īrass is more malleable than bronze or zinc. Nor is it suitable for marine uses, because the zinc reacts with minerals in salt water, leaving porous copper behind marine brass, with added tin, avoids this, as does bronze.īrass 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. Brass is not as hard as bronze, and so is not suitable for most weapons and tools. The composition of brass, generally 66% copper and 34% zinc, makes it a favorable substitute for copper in costume jewelry and fashion jewelry, as it exhibits greater resistance to corrosion. It is used extensively for musical instruments such as horns and bells. Brasses with higher copper content are softer and more golden in colour conversely those with less copper and thus more zinc are harder and more silvery in colour.īrass is still commonly used in applications where corrosion resistance and low friction are required, such as locks, hinges, gears, bearings, ammunition casings, zippers, plumbing, hose couplings, valves, and electrical plugs and sockets. It has also been widely used to make sculpture and utensils because of its low melting point, high workability (both with hand tools and with modern turning and milling machines), durability, and electrical and thermal conductivity. Historically, the distinction between the two alloys has been less consistent and clear, and increasingly museums use the more general term " copper alloy." īrass has long been a popular material for its bright gold-like appearance and is still used for drawer pulls and doorknobs. Both bronze and brass may include small proportions of a range of other elements including arsenic (As), lead (Pb), phosphorus (P), aluminium (Al), manganese (Mn), and silicon (Si). In use since prehistoric times, it is a substitutional alloy: atoms of the two constituents may replace each other within the same crystal structure.īrass is similar to bronze, another copper alloy that uses tin instead of zinc. 1500.īrass is an alloy of copper (Cu) and zinc (Zn), in proportions which can be varied to achieve different colours and mechanical, electrical, and chemical properties, but copper typically has the larger proportion. Attributed to Aert van Tricht, Limburg (Netherlands), c. Islamic Golden Age Brass astrolabe Brass lectern with an eagle. For other uses, see Brass (disambiguation).
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