Galvanized Iron And Steel

Iron and steel articles sometimes are coated with zinc to prevent them from rusting. In the early 1800's, wrought iron coated with zinc became known as galvanized iron. Later, when steel products also were coated with zinc, the name galvanized iron was still used to describe them. At present, much more steel than iron is coated with zinc.

Steel or iron articles that have been cleaned with acid are galvanized by dipping them in a bath of melted zinc. This process is called hot-dip galvanizing. Manufacturers use it to coat steel sheets, pails, pipes, nails, wire, and other products. When the zinc cools on the product, it leaves small drops of zinc, or crystals, on the surface of the iron or steel. This gives galvanized iron a spotted, or mottled, appearance.

Steel or iron articles also are galvanized by placing them in a solution is which zinc or zinc salts are dissolved. With the aid of electricity, the zinc is plated (transferred) onto the articles. This process is called eletrogalvanizing. Although the use of electricity in galvanizing is a modern development, the first zinc-coating process was named after the Italian scientist Luigi Galvani. Galvani in the late 1700's made some of the pioneering studies of electricity.

Galvanized iron is used mostly to make plain and ridged sheets for the roofs and sides of buildings. It is used widely for buildings in tropical and semitropical countries where the damp air rusts metals and rots wood quickly. Sulfurous compounds destroy the finish of galvanized iron. For this reason, it should not be placed where it will come in contact with smoke containing a large amount of sulfur.