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Galvalume vs Galvanized: Which One Is Right for You?
When selecting steel coils or panels for metal roofing, wall cladding, and structural applications, buyers often face the question: Should I choose Galvalume or Galvanized steel?
Both are widely used protective coatings, but their chemical composition, durability, corrosion resistance, and lifecycle cost differ significantly. Understanding these differences is crucial for making a cost-effective, long-term decision.
Table of Contents
- What Is Galvanized Steel (G90, Z275)?
- What Is Galvalume (AZ50, AZ150)?
- Coating Composition & Thickness Standards
- Corrosion Resistance & Lifespan
- Performance in Coastal & Industrial Environments
- Formability, Cutting, and Installation
- Appearance, Painting Systems, and Color Retention
- Cost Analysis & Lifecycle Value
- Typical Applications
- Galvalume vs Galvanized Quick Comparison
- FAQs
- Typical Applications
What Is Galvanized Steel (G90, Z275)?
Process: Hot-dip coating with pure zinc (>99%).
Mechanism: Protects steel via sacrificial anode effect, delaying red rust.
Common Grades:
G90 (ASTM A653): 0.90 oz/ft² coating weight (≈20 μm per side).
Z275 (EN 10346): 275 g/m² coating (double-sided).
What Is Galvalume (AZ50, AZ150)?
Composition: ~55% aluminum, 43.5% zinc, 1.5% silicon.
Grades:
Mechanism: Combines zinc’s galvanic protection and aluminum’s barrier resistance, achieving superior corrosion protection.
👉 Industry studies show Galvalume’s service life is 2–4 times longer than Galvanized steel in most environments.
Coating Composition & Thickness Standards
| Standard | Galvanized (Zn) | Galvalume (Al-Zn) |
|---|---|---|
| ASTM | G30, G60, G90 | AZ50, AZ55 |
| EN | Z100–Z350 | AZ70–AZ185 |
| JIS | SGCC, SGCH | SGLCC |
Corrosion Resistance & Lifespan
Galvalume: Typically lasts 40–50 years in normal inland exposure, with warranties up to 45–50 years (AZ55 bare, AZ50 painted).
Galvanized G90: Average service life of 15–20 years, depending on coating thickness and environment.
In salt-laden coastal air: Galvalume outperforms Galvanized significantly, but cut edges must be sealed or overlapped properly.
Performance in Coastal & Industrial Environments
Coastal areas: Use AZ150 Galvalume with PVDF paint system for maximum resistance.
Industrial zones: Acidic gases accelerate zinc corrosion; aluminum-rich coatings resist better.
Recommendation: Avoid bare galvanized sheets near seashores.
Formability, Cutting, and Installation
Minimum bend radius: ~2T (Galvalume requires slightly larger radius than galvanized).
Cut edges: Must be sealed, overlapped, or protected to avoid localized corrosion.
Fasteners: Use corrosion-matched self-drilling screws with EPDM washers.
Appearance, Painting Systems, and Color Retention
Galvanized: Matte gray, uniform surface.
Galvalume: Shiny, spangled metallic look.
Paint Systems: Polyester (PE), Silicone Modified Polyester (SMP), Polyvinylidene Fluoride (PVDF).
Best choice for long-term aesthetics: PVDF-coated Galvalume panels.
Cost Analysis & Lifecycle Value
Initial cost: Galvalume is slightly more expensive.
Lifecycle Cost (LCC): Longer repainting intervals, fewer replacements, better warranties.
ROI: In harsh climates, Galvalume offers lower total cost of ownership.
Typical Applications
Galvanized (G90, Z275): Interior panels, ducting, fencing, temporary structures.
Galvalume (AZ50, AZ150): Metal roofing, wall panels, agricultural buildings, coastal warehouses, industrial plants.
Galvalume vs Galvanized Quick Comparison
| Factor | Galvalume (AZ) | Galvanized (Z) |
|---|---|---|
| Coating | 55% Al-Zn-Si | Pure Zn |
| Corrosion Resistance | 2–4× higher | Lower |
| Warranty | 40–50 years | 15–20 years |
| Cost | Moderate | Lower |
| Best Use | Roofing, coastal, industrial | Inland, low-budget |
FAQs
Yes. AZ50 often outperforms G90 in corrosion resistance, especially for roofing and siding.
AZ150 Galvalume + PVDF paint system.
~20 μm per side.
Yes, factory prepainted Galvalume panels (PPGL) offer excellent durability.
Conclusion & Buyer’s Checklist
✅ For inland, budget-conscious projects → G90 or Z275 galvanized steel.
✅ For long-term durability, coastal, or industrial environments → AZ150 Galvalume with PVDF coating.
✅ Always specify:
Base metal grade (ASTM A792/A653)
Coating weight (AZ50, AZ150, G90, Z275)
Paint system (PVDF/SMP/PE)
Warranty requirements (≥40 years for roofing)
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