When it comes to the type of metal siding and roofing to select from, there are two options: 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 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 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 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 metals 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 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 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 metal corrodes in a linear fashion and eventually depletes the zinc coating entirely. Galvalume, on the other hand experiences some corrosion, but on a smaller and less significant scale. Galvalume will not breakdown completely, as galvanized will.
To resist corrosion initiated at panel bends and damage sites, Galvalume coated steel is a better choice of substrate.
Galvalume is a trademark of BIEC International Inc.
Based on 30-year atmospheric corrosion R&D tests, Galvalume is projected to outlast galvanized in various atmospheres by up to nine times. Galvalume sheet has also exhibited excellent corrosion resistance in a variety of accelerated tests and atmospheric exposures and on buildings. It has demonstrated equal or better performance than prepainted G90 galvanized in corrosion at flat areas, paint damaged areas, formed areas and roof drip edges.
Up to 10 Years:
Galvanized initially may be more effective, but does not sustain.
10 to 15 Years:
Galvalume begins to outperform galvanized
Over 15 Years:
Superior performance of Galvalume is increasingly evident.