A metal roof will be exposed to rain, humidity and harsh weather conditions. Metal manufacturers use different types of rust-blocking coatings to protect against corrosion. These coatings are applied between the steel substrate and the layer of paint. If the paint happens to get scratched, the rust-block coating is exposed and will prevent rust from reaching the steel substrate. There are two common forms of rust-blocking coatings, galvanized and Galvalume®.
Some manufacturers, including what we at DYMI Construction install, offer a rust-blocking coating called Galvalume®, which mixes aluminum and zinc. Aluminum is highly resistant to corrosion. The aluminum will stop any rust that may occur in the zinc, and the steel will remain intact. After this small amount of edge-rust, Galvalume offers up to 4 times the protection of comparable options. Galvalume® is also offered in three common levels of protection: AZ35, AZ50 and AZ55. The higher the number, the thicker the layer of aluminum/zinc that will protect your metal.
Galvanized has long been the industry standard coating for rust prevention. This coating uses rust-inhibiting zinc, which protects the steel core from corrosion at the panels edges and any surface cracks or scratches. The thicker the layer of zinc, the longer you have before it corrodes away and exposes the steel substrate. Galvanized is offered in three levels of protection: G40, G60 and G90. A G40 coating has .40 ounces of zinc per square foot of panel.
So no matter who you choose for your metal roofing project and we do hope you choose DYMI Construction, you don’t have to worry about rust being an issue for your new metal roof.