Galvanizing, a process by which iron or steel is coated with zinc to protect it from rust and improve its appearance.
In the hot-dip process of galvanizing, the iron or steel materials are first pickled by dipping them in a sulfuric acid solution to remove dirt, grease, and rust. They are then dipped in a bath of molten zinc. A mottled, frosty-appearing layer of zinc adheres to the metal when it is removed from the bath. This process is used with such products as pails, sheet-metal ducting, corrugated metal roofing and siding, and nails.
In the electrolytic process, also called electrogalvanizing, the iron or steel is suspended in a bath of zinc sulfate and sulfuric acid, or zinc cyanide and sodium cyanide. When the current is turned on, a thin but durable coating of zinc is deposited on the metal. This process is used particularly for galvanizing wire and bolts, but may also be used for coating other products.
In sherardizing, small parts are coated with zinc dust in a rotating drum. They are then tumbled for several hours at a high temperature.
The first iron galvanizing process was devised by Henry Crawford of England in 1837. The process derived its name from Luigi Galvani, an Italian scientist, whose experiments in electricity laid the basis for electrogalvanizing.