Galvannealed (or galvanneal) Steel is acarbon steel sheet coated with zinc on both sides by the continuous hot-dip process. Immediately as the strip exits the coating bath, the molten zinc coating is subjected to an in-line heat treatment that converts the entire coating to a zinc-iron alloy. (The iron diffuses from the steel into the coating.) The galvannealed surface has a non-spangled matte finish, a finish very different than the highly metallic appearance of thegalvanized coating. At times, the galvannealed coating may appear similar to uncoated cold rolled steel. One of the primary attributes of the galvannealed coating is that the surface accepts paint very readily. It can be painted without the application of a pretreatment, although a pretreatment will enhance the performance after painting.

   Galvanized steel is defined as a carbon steel sheet coated with zinc on both sides. Continuous hot dipping, or electro-galvanizing are the two processes used to produce galvanized sheet and coil. Generally speaking, the hot dip process consists of passing the steel through a bath of molten zinc. The electro-galvanizing process consists of the application of zinc by electrolytic disposition. The result is a layer of zinc tightly adhering to the base metal through an iron-zinc bonding layer.The zinc not only serves as a barrier between the steel and the environment, it will sacrifice itself to protect the underlying steel sheet. Sacrificial, or galvanic protection occurs when two dissimilar metals are in contact and coupled with water and oxygen. Zinc corrodes preferentially to the iron in steel. This protection prevents corrosion of the steel at areas not covered with zinc. Thus, the spread of corrosion from cut edges, drill holes, etc. is minimized.