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Galvanizing

zinc coating process flux

Galvanizing, industrial process for coating iron or steel with a thin layer of zinc to prevent rusting. It was discovered in 1742 but only named in 1830 after Luigi Galvani (1737–98), who demonstrated that 2 unlike metals in contact produce an electric current, though he did not know why. There are several stages in galvanizing. The metal is thoroughly cleaned with solvents and acid, and a zinc ammonium flux is applied. The article is dipped into a bath of molten zinc kept at about 842°F (450°C), and a coating of layers of iron-zinc alloys or pure zinc forms. Finally, the article may be quenched in cold water to remove the flux and freeze the coating. Small items like nails are galvanized in wire baskets; sheet and wire are treated continuously in an automatic process. The sheet is widely used in building, automobile manufacture, and outdoor structures. In an alternative process, electrogalvanizing, a flow of electricity through a zinc sulfate solution causes a layer of zinc to adhere to steel.

See also: Electroplating.

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