When it comes to the type of metal siding and roofing to select from, there are two options: Galvanized Steel Coil and Galvalume Steel Coil.

Galvanized Steel Coil is a sheet of steel that has been coated with a thin layer of zinc oxide. The zinc is applied to protect the steel from the elements that can lead to corrosion and rust. This corrosion and rust will eventually weaken the metal and lead to a complete breakdown of the steel. Galvanized Steel Coil may begin to breakdown within 10 to 15 years of element exposure.

This corrosion isn’t immediate with Galvanized Steel Coils. Initially, Galvanized Steel Coil maintains its appearance even better than Galvalume Steel Coil. This initial appearance begins to deteriorate and, it does so fairly quickly. The zinc coating begins to corrode at the cut edge and over time it corrodes completely the entire surface of the steel. This effect continues across the entire span of the metal.

Galvalume Steel Coils are made with steel panels having a coating of corrosion-resistant aluminum-zinc alloy applied by a continuous hot dip process. The nominal composition of the coating is 55% aluminum, 43.5% zinc and 1.5% silicon. Galvalume Steel Coil is the trade name for this patented sheet steel product. The alloy coating of aluminum and zinc combines the best properties of both metals. It has the corrosion resistance and heat reflectivity characteristic of aluminum coatings, with the formability and galvanic protection of cut edges characteristic of zinc coatings.

Galvalume Steel Coil is an excellent product for long-life roofing and siding material. The aluminum additive, along with the zinc, allows small particle areas to form within this coating. Any corrosion that occurs does so within these open particle areas. Galvanized steel coil corrodes in a linear fashion and eventually depletes the zinc coating entirely. Galvalume Steel Coil, on the other hand, experiences some corrosion, but on a smaller and less significant scale. Galvalume Steel Coils will not breakdown completely, while Galvanized Steel Coils will.