When ferrous metal (metal containing iron) is exposed to air, it readily oxidizes, or rusts, weakening the metal and making it unsuitable for use as a building material. On the other hand, zinc is very resilient to rust and can be used to protect other metals from the harmful effects of air.
Galvanized metal is metal that has been applied with molten zinc. The zinc chemically bonds with the iron or steel, giving it a thin, permanent layer of zinc.
Zinc is typically applied through a process called hot-dip galvanization, in which the original metal is placed into a pool of molten zinc.
Invention of Galvanization
Hot-dip galvanization was invented by French astronomer Paul Jacques Malouin in 1742.
Because zinc does not rust easily, it acts as a rust-preventing barrier for the iron or steel it surrounds, allowing galvanized metal to be used in a variety of places that would not be suitable for non-galvanized metal.
Normal paints will not adhere to galvanized metal, so a special primer needs to be applied before painting.