Nearly all the steel you use has a protective coating to prevent corrosion. The common term tends to be “galvanized steel,” but it does not accurately describe a coating that has been around since 1972 when it was developed by Bethlehem Steel.
Galvalume® is a tough, durable coating used to protect steel from corrosion. Galvalume may also be found under other licensed trade names and brand names. It provides a number of benefits beyond corrosion-resistance, but before we get to that, let’s take a look at what Galvalume is and when to use it.
A Galvalume Overview
Galvalume is created using a 55% to 45% ratio of aluminum to zinc alloy with a small amount of silicon to ensure durable and even adhesion. The aluminum is what differentiates Galvalume from galvanized steel.
Galvanization only includes the zinc alloy. Steel coated with Galvalume appears similar to galvanized steel but with a smoother appearance. Any visible crystals are smaller and closer together than the process of galvanization.
Galvalume is applied to both sides of cold-rolled steel sheets using a hot-dip process that protects edges as well. Using both zinc and aluminum in the coating takes advantage of the properties of aluminum to add primary protection above and beyond zinc.
Aluminum acts as barrier protection, whereas zinc provides self-healing properties against scratches. The zinc also acts as a sacrificial layer prolonging the life of the steel underneath.
Galvalume and Galvanized Coatings Are Not the Same
Galvanization was developed about 200 years ago. Carbon steel is dipped in molten zinc. A chemical bond is made between the steel and the zinc, creating a crystalline surface.
Due to the chemical bonding, it is more difficult to damage the coating through abrasion. It also continues to protect cut edges. However, as the coating wears down or if it is penetrated sufficiently, corrosion begins to occur which will eventually cover the entire surface. As the corrosion spreads, the steel beneath the bonded layer will shed the galvanized layer.
Galvalume, a mixture of aluminum and zinc, includes all the advantages of galvanization plus increased protection against corrosion. Zinc still bonds with the steel to create a barrier to moisture. Aluminum, which naturally resists corrosion, coats the steel for additional protection. It also increases reflectance.
The aluminum slows the corrosion process as long as the coating is not interrupted by a nick or scratch. Fortunately, aluminum also keeps any corrosion in the damaged area from spreading to the rest of the panel.
The Benefits of Galvalume
The primary benefit of Galvalume is corrosion resistance. The addition of aluminum increases the coating’s corrosion resistance by a factor of two. If the steel panel is in an area where heavy salt-spray and high humidity predominate, Galvalume provides the most robust protection. Marine environments are hard on most materials. Galvanization alone isn’t enough.
- Galvalume does not add significant weight to the steel, retaining the metal’s high strength-to-weight ratio. The coating is every bit as strong and durable as the steel itself. The coating is flexible and will not crack or flake as the sheet metal is bent or formed.
- Steel coated with Galvalume also has superior reflectance in the sunlight. High reflectance reduces heat absorption through the roof panels. With the addition of re-emissive pigments, you will have both energy efficiency and protection from corrosion. With appropriate insulation under the roof, you will reduce cooling costs in the summer and heating costs in the winter. Galvalume also has resistance to high temperatures.
- Besides energy efficiency, Galvalume coated steel costs less than stainless steel and about the same as galvanized steel. Like all steel products, maintenance and repair needs are minimal, providing more cost savings. Unpainted Galvalume can last more than 40 years without appreciable change in appearance. In rural and industrial environments, Galvalume is projected to have a service life of 40 to 60 years.
A galvanized steel roof will start showing its age after 10 to 15 years and has a lifespan of about 15 to 20 years, half that of Galvalume.
- Cut edges in premanufactured panels also have a long-term barrier against rust and corrosion when Galvalume is used as a coating. As long as the coating is not penetrated and the edges remain uncut, the steel will be protected against the elements. Zinc provides galvanic protection for uncut panels.
- Galvalume steel panels can be installed over existing surfaces from asphalt shingles to wood underlayment. It can be used for both structural and architectural roofing needs.
- Steel with Galvalume is a versatile material. It is easily rolled, bent, stamped and fabricated without losing the protection of the coating. There is very little Galvalume won’t survive in terms of formability.
Galvalume also enhances fire resistance.
A Caveat: Where You Should Not Use Galvalume
Galvalume, for all its superior benefits, is sensitive to highly alkaline environments. It should not be used on, in, or around concrete or mortar. Regardless of whether the members are painted or not, Galvalume panels deteriorate quickly in this type of environment.
Galvalume is only protective if the coating remains unbroken. Using Galvalume panels with exposed fastener steel roofing is not recommended. It’s better suited to standing seam metal roof applications with concealed fasteners to avoid exposing a cut edge to the environment.
Galvalume steel provides all the benefits of structural steel while maintaining maximum resistance against corrosion in almost any environment.
Galvalume steel can remain its pristine, sparkly gray or can be painted in any color. Panels can be rolled, stamped and textured to appear like any type of roofing or wall panels you desire.
Galvalume steel is resistant to fire and reflects heat from the sun, saving both insurance and utility costs. Easy to install, Galvalume steel is a versatile material that can be used anywhere stainless steel can be used.
As with all steel products, Galvalume steel requires minimal maintenance. Steel roofs are longer lasting than traditionally shingled roofs, meaning fewer replacements over the life of the structure. Its light weight and high strength make it an ideal material for multi-story construction.
SteelRoofing.com estimates that 40 billion square feet of Galvalume steel has been used in roofing worldwide, an area over 186 times as big as Texas. That's a lot of roofs to protect, and Galvalume is up to the test.