Galvanizing

galvanizing, process of coating a metal, usually iron or steel, with a protective covering of zinc. Galvanized iron is prepared either by dipping iron, from which rust has been removed by the action of sulfuric acid, into molten zinc so that a thin layer of the zinc remains on the surface of the iron upon removal or by a method of electroplating. Iron is also coated with zinc by a method in which the iron is first covered with the zinc dust and then baked; an alloy is formed at the surface, the resulting product being known as sherardized iron. Sheets of pure iron, copper iron, and various steels, as well as wire and netting, are often galvanized, since the zinc coating resists oxidation and the action of moisture very successfully. When the coating is broken or pierced some protection is still afforded, since the zinc reacts with the corroding agent first.

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galvanizing

Protection of iron or steel against exposure to the atmosphere and consequent rusting by application of a zinc coating. Properly applied, galvanizing may protect from atmospheric corrosion for 15–30 years or more. If the coating is damaged, the iron or steel continues to be protected by sacrificial corrosion, a phenomenon in which atmospheric oxidation spares the iron and affects the zinc (as long as it lasts). See also terneplate.

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Galvanizing

The generic term for any of several techniques for applying thin coatings of zinc to iron or steel stock or finished products to protect the ferrous base metal from corrosion; more specifically, the hot dipping that is widely practiced with mild steel sheet and corrugated sheets. During dipping, molten zinc reacts with the steel to form a brittle zinc-iron alloy. For marine use, magnesium is added.

An electrolytic process (also called cold galvanizing or electrogalvanizing) is also used for wire, as well as for applications requiring deep drawing. An alloy layer does not form, hence the smooth electroplated coating does not flake in the drawing die. See Metal coatings