Metal (or their alloys) with relatively low melting points. Such metals include zinc, cadmium, tin, antimony (here counted as a metal), lead, and bismuth, some of which are quite toxic. In Britain, the fine art trade uses the term "white metal" in auction catalogues to describe foreign silver items which do not carry British Assay Office marks, but which are nonetheless understood to be silver and are priced accordingly. A heavy metal is any relatively dense metal or metalloid. More specific definitions have been proposed, but none have obtained widespread acceptance. Some heavy metals have niche uses, or are notably toxic;
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