Galvalume vs. Galvanized Metal Roofing: What's the Difference and Which Should You Choose?
What each coating does, how they compare in corrosion resistance, and when to use each one.
When you're ordering metal roofing panels, you'll probably run into the terms “Galvalume” and “galvanized” at some point — and if nobody takes the time to explain them, they can start to sound interchangeable. They're not.
Both coatings protect the steel underneath from rust and corrosion, but they do it differently, they perform differently over time, and the right choice depends on your application.
Here's what you need to know.
The Coatings, Explained
Galvanized steel is coated with pure zinc. Zinc is a reactive metal — it sacrifices itself to protect the steel underneath, a process called cathodic protection. Galvanized steel has been around for well over a century and has an excellent track record.
Galvalume is a newer formulation. Instead of pure zinc, Galvalume uses an alloy of approximately 55% aluminum, 43.5% zinc, and 1.5% silicon. The aluminum provides a barrier coating — it's very resistant to corrosion on its own — while the zinc continues to provide sacrificial protection where it's needed.
The result is a coating that, in most environments, outperforms straight galvanized steel in long-term corrosion resistance. Galvalume has become the industry standard substrate for painted metal roofing panels, and it's what we use as our default for color panels here. The specific grade we stock is AZ50 Galvalume.
How They Compare in Corrosion Resistance
For most roofing applications — residential homes, commercial buildings, agricultural structures — Galvalume holds up better over time than galvanized steel. The aluminum-dominant coating is particularly good at resisting the oxidation and atmospheric corrosion that New England roofs face: humidity, precipitation, freeze-thaw cycles, and salt air near the coast.
Independent testing over decades has consistently shown Galvalume outperforming galvanized in outdoor exposure, particularly in coastal and industrial environments. If you're looking for long-term performance with minimal maintenance, Galvalume is the stronger choice.
Where Galvanized Has the Edge
Galvalume isn't perfect for every situation. There are a few specific cases where galvanized steel performs better:
Cut edges. When a panel is cut, the Galvalume coating is exposed at the cut edge. The zinc component provides some sacrificial protection there, but it's less robust than an uncut panel. Galvanized steel handles cut edges somewhat better because the pure zinc sacrificial protection works more aggressively. This matters most on applications with a lot of exposed cut edges.
Contact with concrete or treated lumber. Galvalume can react with alkalis like cement and concrete, as well as with the preservatives in pressure-treated lumber. If panels are going to be in direct, prolonged contact with either material — think concrete foundations or PT framing — galvanized is typically the safer choice.
Certain agricultural chemical environments. Some agricultural chemicals, particularly fertilizers and animal waste, can accelerate corrosion of Galvalume more than galvanized. If panels are going inside a livestock barn or a space with heavy chemical exposure, it's worth a conversation with us about which substrate is appropriate.
What We Stock and Offer
At Hometown Metal Roofing, Galvalume is our standard substrate for color panels — it's what you're getting unless you specify otherwise. It performs well in virtually all of our service area's roofing applications and carries the Red Dot Galvalume warranty, which covers all of our profiles made on AZ50 Galvalume.
We also offer G-100 Galvanized for Tuff Rib Ag panels. If your project involves any of the specific situations above — contact with treated lumber, concrete exposure, or certain ag environments — it's worth asking about galvanized when you call in your order.
What About Paint?
It's worth noting that the paint system on top of the substrate matters independently of the coating underneath. Our Tuff Rib Ag and Commercial PBR panels use a WeatherXL paint system. Our standing seam profiles — both the Snap Lock and the Nail Flange — use a Kynar paint system, which is more flexible and suited to the tighter bends in standing seam profiles.
The Red Dot Galvalume warranty applies to the Galvalume substrate on any of our profiles. The paint warranties (WeatherXL and Kynar) cover the paint system on top. Both are in play when you order a color panel from us.
The Practical Recommendation
For the majority of roofing projects in New England — residential, commercial, agricultural — Galvalume on an AZ50 substrate is the right choice. It performs better in atmospheric corrosion, carries strong warranty backing, and is the industry standard for a reason.
If your project involves direct contact with concrete, treated lumber, or heavy agricultural chemical exposure, tell us when you call. We'll point you toward the right option.
Questions about which substrate is right for what you're building? Reach out at [email protected] or stop by our shop in Westfield, MA. We're happy to talk it through.
Andrew Kurtz grew up next to one of Pennsylvania's largest roll-forming operations and spent 25 years in construction. He founded Hometown Metal Roofing after identifying that no one in western New England was locally manufacturing Tuff Rib Ag or PBR panels — leaving contractors to wait 1–3 weeks for out-of-state shipments. Hometown Metal Roofing is a division of Hometown Structures, ranked in the top 4% of licensed contractors in Massachusetts.