Galvalume Steel Coil

Galvalume Steel Sheet is carbon steel sheet coated with aluminum-zinc alloy by a continuous hot-dip process. The nominal coating composition is 55% aluminum and 45% zinc. A small but important addition of silicon is included in the coating alloy. It is added not to enhance the corrosion performance, but to provide good coating adhesion to the steel substrate when the product is roll-formed, drawn, or bent during fabrication.

Galvalume steel sheet combines the excellent barrier corrosion protection of aluminum with the galvanic protection of zinc. The result is a coating that lasts a long time, a coating that provides cut-edge protection along sheared edges, and therefore, a coating that offers excellent protection to steel sheet. Although there are a few exceptions, for most applications in most types of environment, Galvalume steel sheet is the preferred product when long-term resistance to atmospheric corrosion is desired. It outlasts a galvanized coating of comparable thickness, and offers cut-edge protection that is not available with aluminum-coated sheet. This cut-edge protection means there is less rust-staining along sheared edges, at scratches, and other imperfections in the coating. Also, since the coating is so resistant to corrosion, it retains a very bright surface appearance when exposed to most atmospheres. These attributes make Galvalume steel sheet the preferred material for roofing.

The superior corrosion resistance of Galvalume steel sheet is achieved by the presence of microscopic zinc-rich and aluminum-rich areas within the coating. The aluminum-rich areas, which corrode very slowly, provide the long-term durability while the zinc-rich areas, which corrode preferentially, provide galvanic protection.