Plain steel is coated with a layer of hot-dipped commercially pure zinc to provide corrosion protection. Zinc is considered a sacrificial element and works well as a metallic coating. When the metal is cut or damaged, the zinc coating will protect that area from corrosion. Galvanized steel is warranted against corrosion for up to 20 years and offers excellent barrier protection. The Metal Roofing Alliance recommends the use of only G-90 for roofing applications.
Galvalume steel combines the metallic coatings of both aluminum and zinc.
This combination joins the healing properties of zinc with the superior barrier protection of aluminum. Galvalume steel offers superior weathering properties and is used in various application weights, the most common being AZ-55. Aluminum Aluminum is an affordable and extremely lightweight roofing material. Aluminum has a high coefficient of expansion, causing some thermal movement. In addition, this material has excellent corrosion resistance and is ideal for coastal environments.