Not all metal panels are created equally. That’s why educating yourself and understanding the different options available is essential.
The three main components in a metal panel are the substrate, paint system, and gauge. You can “see” the paint and “feel” the difference in weight between various panel gauges.
Since the substrate is hidden under the paint and doesn’t change the look or feel of the panel, it’s an element that often flies under the radar of building owners and specifiers. Yet the panel substrate is the backbone of any metal roofing panel.
The most popular steel substrates are Galvanized and Galvalume. While you may (or may not) have the option to choose which substrate you receive, it’s important to understand the differences.
Galvanized substrates are coated with a zinc alloy. The greater the percentage of zinc in the coating, the greater protection the panels offer against corrosion. G100 and G60 are two commonly used Galvanized substrates.
These designations relate to the total zinc on both sides of the panel surfaces. G100 products contain 1.0 ounces of zinc for every square foot of panel, while G60 substrates contain 0.6 ounces of zinc.
While, at first blush, that difference doesn’t appear significant, nothing could be further from the truth. G100 products contain 66% more protective zinc than a G60 substrate. This difference directly impacts panel longevity.
Consequently, you should expect lower cost and performance from G60 products than from G100 products.
GalvalumeⓇ, invented by Bethlehem Steel in 1972, is a combination of 43.5% zinc, 55% aluminum, and 1.5% silicone. Galvalume is the trademarked name for this family of products, also referred to as Zincalume.
This substrate composition combines zinc's sacrificial properties and aluminum's barrier protection. Consequently, it delivers superior performance in almost all applications.
AZ50 is the industry-standard coating level for painted products using this substrate type, and AZ55 for bare (or unpainted panels.) These designations refer to the amount of zinc-aluminum coating on the panels. AZ50 coatings contain .50 ounces per square foot on both sides of the panel, and AZ 55 contains .55 ounces per square foot. Higher coating levels provide improved performance.
Proper Product Selection
So which is better? That depends on the type of project. For animal confinement projects, we recommend Galvanized panels. Using the highest level of zinc panels possible for animal confinement projects is also essential, so leaning to G100 products is a great move.
This recommendation is based on our 49+ years of experience seeing the adverse reaction between animal waste and Galvalume. With that said, we have some poultry customers using Galvalume and experiencing acceptable results.
The difference appears to lie in the fact that poultry excrements are drier than the more watery excrements of other livestock such as cattle, horses, and swine.
Outside of animal confinement projects, we always recommend Galvalume substrates. We base that decision on over four decades of testing and photos like those below showing that Galvalume simply offers better long-term corrosion resistance than Galvanized products.
We’re proud to provide both Galvanized and Galvalume substrates to offer our customers the greatest flexibility.
Contact us if the manufacturer you’re working with doesn’t offer your desired substrate. We’re happy to help!
Since 1963, McElroy Metal has served the construction industry with quality products and excellent customer service. The family-owned components manufacturer is headquartered in Bossier City, La., and has 14 manufacturing facilities across the United States. Quality, service and performance have been the cornerstone of McElroy Metal’s business philosophy and have contributed to the success of the company through the years. As a preferred service provider, these values will continue to be at the forefront of McElroy Metal’s model along with a strong focus on the customer.