With 20 years of commercial and residential roofing throughout Taxas Alpine Sheet Metal Systems are the industry leaders in installing Metal Roofing including Galvanized Steel Roofing. Because the traditional carbon/iron steel alloy is rust prone when exposed to the elements, steels used for the metal roofing industry are coated with a specific thickness of another metal or alloy on both sides of the base carbon/iron steel strip. The process used to accomplish this is called the hotdip process, and involves running the steel through a molten bath of the metal to be applied. The hot-dipped process is basically a cheaper, more efficient alternative to a similar process with which you may be pretty familiar: electroplating.
Steels, then, are classified and named according to the metal that is applied. Galvanized steel is base carbon/iron steel with a metallic coating of zinc. The coating metal offers two kinds of protection: galvanic or barrier. Galvanic protection is a self-sacrificial process by which the metal coating gives itself up, rather than allow the base metal to corrode. Barrier protection is simply that the coating metal keeps the elements from reaching the base metal.
In the metal roofing industry, galvanized steel is used more often than any other metal and, and has a great affinity to hold paint. Because zinc provides galvanic protection, scratches on galvanized steel are somewhat self-protected or “band-aided,” preserving the steel from rust. Therefore, the life-span of galvanized steel depends largely on the thickness of its metallic coating, since the more zinc that is present, the longer the steel is able to remain protected and rust-free. G-90, the
most common zinc thickness used in the metal roofing industry, means that 0.90 ounces of zinc are coated per square foot of steel surface