When choosing between Galvalume (55% Al-Zn alloy-coated steel) and Galvanized (pure zinc-coated steel) for roofing applications, consider their corrosion resistance, lifespan, cost, and aesthetics. Below is a detailed comparison:
1. Composition & Coating
| Property | Galvalume (AZ55) | Galvanized (GI) |
| Coating | 55% Aluminum, 43.4% Zinc, 1.6% Silicon | 99% Zinc |
| Coating Weight | 20–150 g/m² (0.9–6.0 oz/ft²) | 30–275 g/m² (1.0–9.0 oz/ft²) |
| Base Metal | Cold-rolled steel (e.g., DX51D, DX52D) | Cold-rolled steel (e.g., SGCC, SGCH) |
Key Insight:
Galvalume’s aluminum content provides heat reflection and barrier corrosion resistance, while zinc in galvanized steel offers sacrificial protection.
2. Performance Comparison
(a) Corrosion Resistance
Galvalume:
Outperforms galvanized steel in marine and industrial environments (aluminum oxide layer resists salt and chemicals).
Lasts 2–4× longer than galvanized in harsh climates (e.g., 30+ years vs. 15–20 years).
Galvanized:
Better for rural/mild climates; zinc sacrificially corrodes to protect steel.
Prone to white rust in humid conditions if not properly ventilated.
(b) Heat Reflectivity
Galvalume: Reflects 80%+ of solar heat, reducing cooling costs (ideal for hot climates).
Galvanized: Absorbs more heat, increasing attic temperatures.
(c) Durability & Scratch Resistance
Galvalume: Harder coating resists mechanical damage during installation.
Galvanized: Softer zinc scratches more easily but self-heals via galvanic protection.
(d) Appearance and Color
Galvanized: The surface is bright silver. Over time, it will gradually darken due to the corrosion of the zinc layer, and white rust will be generated, which affects the beauty.
Galvalume: The surface is dark silver (similar to aluminum plate). After oxidation, a uniform gray rust is formed, and the appearance is more durable and consistent, which is suitable for buildings with high – aesthetic requirements.
3. Cost & Availability
| Factor | Galvalume | Galvanized |
| Material Cost | 10–20% higher than galvanized(Some mill price same with GI) | Lower upfront cost |
| Maintenance | Minimal; long-term savings | May require repainting/rust treatment |
| Availability | Widely stocked | More common globally |
4. Aesthetics & Finish Options
Galvalume: Bright, spangled appearance (natural metallic look).
Compatible with PVDF/polyester paint for colored roofs (e.g, Puralac finish).
Galvanized: Dull gray matte finish; often painted for aesthetics.
Limited color retention vs. painted Galvalume.
5. Best Applications
| Scenario | Recommended Choice | Reason |
| Dry inland areas, short – term buildings | Galvanized | Low cost, basically meeting the medium – life requirements. |
| Coastal, high – humidity, industrial areas | Galvalume | Stronger corrosion resistance, longer service life, reducing maintenance costs. |
| High – temperature environments (such as solar roofs) | Galvalume | Better heat resistance, not easy to fail due to high temperature. |
| Buildings with high aesthetic requirements | Galvalume | More stable appearance, and the consistency of the gray rust layer is better than that of the white rust. |
| Projects with limited budget | Galvanized | Lower initial cost, suitable for temporary or low – cost buildings. |
6. Installation Tips
Galvalume:
Use aluminum-compatible fasteners (e.g., stainless steel) to prevent bimetallic corrosion.
Avoid cutting/grinding on-site to preserve coating integrity.
Galvanized:
Ensure proper ventilation to prevent condensation-induced white rust.
Touch up scratches with zinc-rich paint.
7. Industry Standards
Galvalume: ASTM A792, EN 10346 (DX51D+AZ150).
Galvanized: ASTM A653 (G90, G60), EN 10346 (Z275).
Conclusion
Galvalume: Offers superior corrosion resistance, heat resistance, and longevity, resulting in lower overall long-term costs. It is suitable for coastal areas, highly polluted environments, high-temperature environments, or buildings requiring high durability and aesthetics.
Galvanized: Offers a high cost-effectiveness and is suitable for dry environments, short-term use, or budget-constrained scenarios. However, it has a shorter lifespan and average corrosion resistance.
03Jan
03Jan
06Jan
12Jan
13Jan
14Jan
Our mission is to be the pioneer of product, cost solution and service concept in steel industry chain.
COPYRIGHT © 2025 | TIANJIN RUNFEI TRADE CO., LTD
