Galvalume vs Galvanized

The difference between Galvalume, and Galvanized Steel

The difference between Galvalume, and Galvanized Steel

If you start looking into metal roofing, it won’t be long before you hear the term GALVALUME®.  So what is that , and how does it work?

What is Galvalume Steel

Galvalume was developed in 1972.  Essentially it is a 55% aluminum to 45% zinc alloy coated sheet steel.  This blend is what makes it different than Galvanized Steel  which is covered with a zinc-only coating. According to BIEC, the licensor, 120 million tons have been produced since 1972, and Steelroofing.com estimates 40 billion square feet of Galvalume steel has been used in roofing worldwide. With GALVALUME, the aluminum and zinc act together to resist corrosion and provide barrier protection on the roofing surface. Zinc alone would allow more rust to occur, while Aluminum alone does not stand up as well to hail and other damaging forces.

What is Galvanized Steel

Galvanized Sheet is carbon steel sheet coated with zinc on two sides by a continuous hot-dip process. This method tightly adheres the coating to the steel with an iron-zinc alloy bonding layer formed by a diffusion process while the heated steel strip is in contact with the molten zinc. One of the drawbacks of Galvanized is that if the Zinc coating is scratched off the steel, the Steel is left unprotected, and is subject to failure.

Galvalume vs. GalvanizedGalvalume vs Galvanized

While both products were developed to essentially sacrifice themselves to protect the steel sheeting they coat, the exposure comparison photo shows that Galvalume® performs (up to nine times) better in fighting corrosion as compared to Galvanized coating. While Galvalume® can initially show signs of corrosion faster than Galvanized, it has a sacrificial property that will prevent the corrosion from growing whereas once corrosion has started on a Galvanized panel, it can continue to corrode until panel integrity is lost. According to a study released by the Metal Construction and Zinc Aluminum Coaters associations, the longevity of a low-slope unpainted Galvalume® standing-seam roof is 60 years Additionally, primer and paint adhere better to Galvalume®-coated panels and they carry a 20-year limited warranty while galvanized panels do not, making them a smarter long-term investment for all building applications.

Conclusion

Another great feature of Galvalume Steel is that as the material is cut, the Zinc and Aluminum combine to prevent corrosion at any exposed edges. Galvalume Steel can be expected to provide at least TWICE the service life of traditional zinc-coatings of similar coating thickness under the same exposure conditions. This has been proven by actual exposure tests using flat coupon samples, conducted over 36 years in the U.S.A. and 15 years in Canada. These tests show that Galvalume has at least TWICE the service life versus Galvanized.

All of the Steel products that we use here at Classic Metals, are manufactured using Galvalume Steel. Feel free to contact us if you have any questions or comments.