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G60 vs G90 Galvanized Steel: Key Differences Explained

When choosing galvanized steel for construction, roofing, or industrial projects, the terms G60 and G90 often appear in specifications. These designations indicate different zinc coating weights, which directly affect corrosion resistance, durability, and cost-effectiveness. Understanding the key differences between G60 and G90 galvanized steel helps engineers, builders, and buyers select the right material for their applications. At Hengze Steel, we provide both grades to meet diverse project needs.

1. Introduction to G60 and G90 Galvanized Coating Designations
1. Introduction to G60 and G90 Galvanized Coating Designations

2. Zinc Coating Weight and Thickness Comparison
2. Zinc Coating Weight and Thickness Comparison

3. Corrosion Resistance and Service Life
3. Corrosion Resistance and Service Life

4. Cost and Economic Considerations
4. Cost and Economic Considerations

5. Applications: When to Use G60 vs. G90?
5. Applications: When to Use G60 vs. G90?

6. Industry Standards and International Equivalents
6. Industry Standards and International Equivalents

7. How to Select the Right Galvanized Grade
7. How to Select the Right Galvanized Grade

1. Introduction to G60 and G90 Galvanized Coating Designations

G60 and G90 are coating weight designations defined under ASTM A653 – Standard Specification for Steel Sheet, Zinc-Coated (Galvanized) by the Hot-Dip Process. These designations refer specifically to the zinc coating mass applied to both sides of the steel sheet or coil, not the strength of the steel substrate itself.

G60 = 0.60 oz/ft² of zinc coating (total on both sides).
G90 = 0.90 oz/ft² of zinc coating (total on both sides).

At Hengze Steel, we supply both G60 and G90 galvanized steel coils and sheets to meet diverse environmental and project requirements.

2. Zinc Coating Weight and Thickness Comparison

Coating Grade	Coating Weight (total, oz/ft²)	Approx. Mass (g/m², both sides)	Coating Thickness (per side, µm)	Typical Use Case
G60	0.60	~180 g/m²	5–8 µm	Adequate protection in moderate indoor/outdoor environments
G90	0.90	~275 g/m²	18–20 µm	Superior durability for outdoor, coastal, or industrial settings

Key Insight: G90 has approximately 50% more zinc than G60, which translates into significantly better corrosion resistance and longer lifespan in harsh conditions.

3. Corrosion Resistance and Service Life

Stronger Protection: With its thicker zinc coating, G90 offers enhanced resistance to moisture, salt spray, and industrial pollutants compared to G60.
Extended Lifespan: In moderately corrosive environments, G90 galvanized steel can last 30–50% longer than G60 before requiring maintenance.
Reduced Maintenance: G90 requires fewer inspections and recoating over its lifetime, while G60 may show red rust earlier in humid or semi-exposed conditions.

Hengze Steel has supplied G90 galvanized coils to construction and roofing projects in coastal regions, where long-term durability is critical.

4. Cost and Economic Considerations

Material Cost: G90 is more expensive than G60 due to its higher zinc content and longer galvanizing process.
Formability: Thicker zinc coatings may be more prone to flaking or cracking during deep drawing, bending, or stamping. G60 is slightly more formable.
Lifecycle Economics: Although G90 has a higher upfront cost, it lowers overall maintenance and replacement expenses, making it more economical for long-term projects.

5. Applications: When to Use G60 vs. G90?

Environment / Application	Recommended Grade	Why
Indoor or light moisture exposure (HVAC ducts, indoor wall panels, electrical enclosures)	G60	Sufficient corrosion protection at a lower cost
Moderate outdoor exposure (warehouses, roofing underlayment, framing members)	G60 or G90	Choice depends on exposure to rain and humidity
Harsh outdoor / coastal environments (roofing sheets, siding, fencing, marine structures)	G90	Thicker zinc layer offers superior long-term protection
High-visibility, long-life projects (roof panels, wall cladding, structural decking)	G90	Extends service life and preserves appearance

At Hengze Steel, our engineers often recommend G90 galvanized steel for clients in coastal, industrial, or high-humidity markets where durability is essential.

6. Industry Standards and International Equivalents

ASTM A653: Governs G30, G40, G60, G90, up to G360 coating weights for hot-dip galvanized steel sheet and coils.
ASTM A123: Applies to batch hot-dip galvanizing of fabricated steel products (different from continuous sheet galvanizing).
International Equivalents:
- G60 ≈ Z180 (EN 10346 standard, ~180 g/m² total)
- G90 ≈ Z275 (EN 10346 standard, ~275 g/m² total)

Hengze Steel provides galvanized steel coils that comply with ASTM, EN, and JIS standards, ensuring compatibility with global construction and manufacturing requirements.

7. How to Select the Right Galvanized Grade

Assess Exposure: Indoor vs. outdoor, coastal vs. inland.
Consider Service Life: Longer design life favors G90.
Evaluate Processing Needs: For deep drawing or bending, confirm coating adherence.
Budget Constraints: G60 is more economical for non-critical applications.
Check Project Specifications: Building codes often specify a minimum galvanized coating weight (e.g., G90 for roofing and siding).

At Hengze Steel, our technical team helps customers balance performance and cost to select the optimal galvanized grade for each application.

Conclusion

The difference between G60 and G90 galvanized steel lies primarily in zinc coating thickness and corrosion protection. G90, with its ~275 g/m² zinc coating, offers superior durability and longer service life, making it the ideal choice for outdoor, coastal, or industrial applications. G60, at ~180 g/m², provides cost-effective protection for indoor or moderate environments.

For reliable supply, competitive pricing, and expert guidance, Hengze Steel delivers premium galvanized steel coils and sheets tailored to your project requirements.