Galvanized steel

Galvanized steel is ordinary steel with a thin coating of zinc on its surface. Bare steel rusts when air and moisture reach it. The zinc stops that, so galvanized steel is used for car bodies, roofing, appliance cases and the inner frames of electronics.

There are two main ways to add the zinc. In hot-dip galvanizing, a long ribbon of cleaned steel sheet runs through a bath of molten zinc at about 450 °C, and jets of air wipe off the excess so the coating is even. In electrogalvanizing, the sheet passes through a zinc salt solution while an electric current plates zinc onto it, giving a thinner, smoother layer that takes paint well. Either way, the zinc bonds tightly to the steel, in a coating only micrometers thick.

Zinc protects steel in two ways. It's a barrier, and because zinc corrodes more readily than iron, it sacrifices itself: even at a scratch or cut edge, the nearby zinc corrodes instead of the steel. In a TV, galvanized sheet is pressed into the back chassis. The name honors Luigi Galvani, the Italian scientist famous for his experiments with electricity and frog legs.