Galvalume vs. Galvanized Steel in Metal Roofing: Key Differences

When selecting materials for metal roofing projects, two popular options are Galvalume (aluminum-zinc coated steel) and Galvanized (zinc-coated steel).

While both provide corrosion resistance, they differ in composition, durability, and ideal applications. Understanding these differences helps contractors and builders make informed decisions for long-lasting roofing solutions.

1. Coating Composition

• Galvalume (55% Aluminum, 43.4% Zinc, 1.6% Silicon):

  • Combines aluminum’s corrosion resistance with zinc’s sacrificial protection.

  • The silicon enhances adhesion to the Steel substrate.

• Galvanized (100% Zinc Coating):

  • Pure zinc layer protects steel through sacrificial corrosion (zinc corrodes first).

2. Corrosion Resistance

• Galvalume:

  • Superior long-term rust protection, especially in harsh coastal or industrial environments.

  • Aluminum forms a protective oxide layer, while zinc provides additional sacrificial protection.

• Galvanized:

  • Effective against rust but may degrade faster in highly corrosive conditions.

  • Zinc coating wears away over time, exposing the steel underneath.

3. Heat Reflectivity & Durability

• Galvalume:

  • Reflects more solar heat, improving energy efficiency.

  • Performs better in high-temperature environments.

• Galvanized:

  • Absorbs more heat, potentially increasing cooling costs.

  • More prone to white rust (zinc oxide) in humid conditions.

4. Cost & Lifespan

• Galvalume:

  • Higher initial cost but offers 2-4 times longer lifespan than Galvanized Steel.

  • Ideal for projects requiring low maintenance and extended durability.

• Galvanized:

  • More budget-friendly upfront but may require earlier replacement in corrosive environments.

5. Best Applications

• Galvalume:

  • Coastal areas, industrial zones, and regions with high humidity or salt exposure.

  • Commercial roofs, agricultural buildings, and premium residential projects.

• Galvanized:

  • Interior applications, dry climates, or short-term roofing solutions.

  • Sheds, garages, and budget-conscious projects.

Conclusion

While galvanized steel is a cost-effective choice for mild conditions, Galvalume excels in longevity and corrosion resistance, making it a preferred option for demanding environments. Builders should assess climate, budget, and project lifespan when selecting the right coating for metal roofing.