Speculum metal metal mixtures usually contain two parts copper to one part tin along with a small amount of arsenic, although there are other mixtures containing silver, lead, or zinc. The knowledge of making very hard white high luster metal out of bronze-type high-tin alloys may date back more than 2000 years in China although it could also be an invention of western civilizations. Such metals were used in sculpture and to make more effective mirrors than the more common yellow easily tarnishing bronze mirrors. In that era mirrors of speculum metal, or any precious metal, were rare and only owned by
Copper alloys in aquaculture UR30 and other mesh forms and a range of copper alloys. To date, in over 10 years of aquaculture experience, chain link mesh fabricated by these brass alloys have not suffered from dezincification, stress corrosion cracking, or erosion corrosion. Copper–nickel alloys were developed specifically for seawater applications over five decades ago. Today, these alloys are being investigated for their potential use in aquaculture. Copper–nickel alloys for marine applications are usually 90% copper, 10% nickel, and small amounts of manganese and iron to enhance corrosion resistance. The seawater corrosion resistance of copper–nickel alloys results in a thin, adherent, protective surface film