There are two types of substrates:
Galvalume® and Galvanized are two popular substrates utilized in the metal roofing and siding industry. Galvanized substrates feature a zinc coating applied to the raw steel while Galvalume substrates feature an alloy of zinc plus aluminum.
Performance testing shows Galvalume offers improved long-term performance and is backed with a 25-year Steel Mill Warranty. Galvanized substrates do not have a Steel Mill warranty. However, galvanized substrates are still popular for many applications, such as animal confinement, and can offer good performance if the grade matches the performance characteristics and long-term customer expectations. Galvanized grades depend on the amount of zinc in the alloy. The simple fact is that the more zinc, the better the performance. For example, a G100 substrate has 66% more Zinc than a G60 substrate and will provide a longer-term resistance to corrosion.
McElroy Max-Rib provides an option of Galvalume® or Galvanized substrates and three different coatings to match your project and long-term performance expectations.
Three types of coatings are available - best, better and good. Kynar 500® (PVDF) coatings are the "best" for long life, color retention and chalk resistance. Silicone Modified Polyester is the "better" coating and performs well in general use. Polyester is the "good" coating and performs well in shade and shelter or basic applications.
McElroy warm-rolls all Max-Rib Silicone Modified Polyester panels. Thermoforming prevents tension-bend cracking, providing corrosion protection for increased longevity, visual appeal, and value.
Know Your Warranty Terms
Often warranties are designed to protect the manufacturer. In fact, warranties are written with acceptable levels of failure. When reviewing and comparing warranties, you should know the following terms.
Fading occurs when the environment attacks the pigment portion of the paint system. When testing for fade, all chalk and other surface impurities are removed using cheese cloth and detergent prior to testing. The test is then conducted in the area that was cleaned, often resulting in a “claim denied”.
Performance Fact: Kynar 500 (PVDF)coatings offer the best protection against fade.
Chalking occurs when environmental conditions cause degradation of the resin. As the resin degrades, it takes on a whitish appearance called chalk. Again, levels of failure are built into the warranty.
Performance Fact: Kynar 500 (PVDF)coatings offer the best protection against chalk.
Film integrity is the ability of the coating to stay adhered to the metal substrate. Film integrity has little to do with fade and chalk ratings. Therefore, a bright red wall/roof can be a muted pink (or even white) with the film still intact. Film integrity is being used in the metal panel industry to extend the length of warranties.
Performance Fact: Kynar 500 (PVDF) coatings offer the best film integrity.
Galvalume® carries a warranty from the steel mills. Galvanized does not. Galvalume® warranty protects against perforation (rust-through) of the substrate. Surface rust, as shown in the photo, is not covered by the Galvalume® warranty.
Performance Fact: Galvalume substrates or high zinc content (G100 or greater) galvanized substrates offer the best protection against corrosion.
Red Rust Warranty:
Most "red rust warranties" protect against the accumulation of rust on the panel's flat areas - away from cut edges, where rust is most likely to occur.
Performance Fact: Proper building design and installation practices will lessen the risk of edge rust.