rust
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Sacrificial metal is used to protect pipes and other exposed metal on oil rigs from corrosion by rust. A more reactive metal than iron, such as zinc or magnesium, is attached in large lumps by conducting wires, at intervals along the pipes. Electrons released during the reaction travel along the conducting wires to the pipes, preventing rust from occurring. It is cheaper to replace the sacrificial metal than it is to replace the pipes.
Reddish-brown oxide of iron formed by the action of moisture and oxygen on the metal. It consists mainly of hydrated iron(III) oxide (Fe2O3.H2O) and iron(III) hydroxide (Fe(OH)3). Rusting is the commonest form of corrosion.
Rust prevention
There are two main approaches to protect against rusting. Barrier methods introduce a barrier between the metal and the air and moisture to minimize the reaction. This is the commonest method of rust prevention and the barrier may consist of a layer of grease, paint, plastic, or an unreactive metal, such as tin, copper, or chromium.In sacrificial protection, the iron is actually covered by a more reactive metal, such a zinc (galvanization), or connected to a more reactive metal, such as magnesium, so that as long as the ‘sacrificial’ metal is present it will corrode first.
rust
In botany, common name for a group of minute parasitic fungi (see fungus) that appear on the leaves of their hosts as orange-red spots, later becoming darker. The commonest is the wheat rust Puccinia graminis, order Uredinales.
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