Galvanized vs Galvalume®
Options to consider for the Best Metal for Siding & Roofing
Here’s something you may not have known: Metal Roofing and Siding actually has two different types of material that can be used. Those options are Galvanized and Galvalume.
Galvanized metal 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 could lead to corrosion and rust. If corrosion or rust take place, it will eventually weaken the metal, and the elements that create the steel will eventually be broken down. Galvanized metal may begin to breakdown within 10 to 15 years of element exposure.
This corrosion isn’t immediate with galvanized metal. Initially, galvanized metal maintains its appearance even better than Galvalume metal. This initial appearance begins to deteriorate, and it does so fairly quickly. The zinc coating begins to corrode at any exposed cut edge, and over time it completely corrodes the surface of the steel.
Galvalume metals are made with steel panels having a coating of corrosion-resistant, aluminum-zinc alloy, which is applied by a continuous hot dip process. This is done to protect it from oxidation. The composition of the corrosion-resistant coating is 55% aluminum, 43.5% zinc and 1.5% silicon. Galvalume 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 is a product engineered specifically to be a long term roofing and siding material. The aluminum additive, along with the zinc, allows small particle areas to form within the coating. Any corrosion that occurs does so within these open particle areas. While Galvanized metal corrodes in a linear fashion and eventually depletes the zinc coating, Galvalume, on the other hand experiences some corrosion, but on a less significant level. Galvalume will not breakdown completely, as opposed to galvanized metal.
In conclusion, Galvalume® is more corrosion-resistant than galvanized steel, but because aluminum provides barrier protection instead of galvanic protection, scratches and cut edges are less protected. Galvalume is offered in both bare and pre-coated versions. Most Galvalume®– like galvanized steel – is coated.