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.