Most copper is used for electrical equipment, construction, such as roofing and plumbing, industrial machineries, such as heat exchangers and alloys. The main long established copper alloys are bronze, brass (a copper-zinc alloy), copper-tin-zinc, which was strong enough to make guns and cannons, and was known as gun metal, copper and nichel, known as cupronickel, which was the preferred metal for low-denomination coins.