G90 Galvanized Steel Sheet: Heavy-Duty Corrosion Resistance for Demanding Environments
Product Overview
G90 galvanized steel sheet is a premium hot-dip galvanized (HDG) product offering 275g/m² total zinc coating (0.90 oz/ft² per ASTM A653), delivering 1,500+ hours of salt spray resistance (ISO 9227). Designed for structural and outdoor applications, this material combines extreme durability with cold-forming versatility. Compliant with ASTM A653, EN 10346, and JIS G3302 standards, G90 outperforms standard galvanized grades in coastal, industrial, and high-humidity environments.
Technical Specifications
1. Base Material & Dimensions
- Thickness: 0.12mm (precision electronics) to 6.00mm (structural beams) with ±0.02mm tolerance
- Width: 600–1,500mm (optimized for roll-forming automation)
- Coating Structure:
- Pure Zinc Layer: 80% of total coating (220g/m²)
- Zinc-Iron Alloy Layers: Gamma (Fe₃Zn₁₀), Delta (FeZn₇), Zeta (FeZn₁₃) phases
2. Coating Performance
| Parameter | G90 (ASTM) | Z275 (EN) | Equivalent |
|---|---|---|---|
| Total Zinc Weight | 275g/m² | 275g/m² | 18.5µm/side |
| Salt Spray Resistance | 1,500hrs | 1,200hrs | ISO 9227 |
| Thermal Stability | Stable to 315°C | Loses 5% coating at 400°C |
Mechanical Properties
| Grade | Yield Strength (MPa) | Tensile Strength (MPa) | Elongation (A80%) | Bendability* |
|---|---|---|---|---|
| DX54D+G90 | 120–220 | 260–350 | ≥36% | 0t (180°) |
| S350GD+G90 | ≥350 | ≥420 | ≥16% | 1t (90°) |
| SGCC+G90 | 140–300 | 270–420 | ≥26% | 0.5t (180°) |
*Minimum bend radius relative to thickness
Manufacturing Process
- Hot-Dip Galvanizing:
- Steel cleaning: 3-stage alkaline degreasing (pH 13, 80°C)
- Continuous annealing: 720°C in 15% H₂ + 85% N₂ atmosphere
- Zinc bath immersion: 455°C with 0.15–0.25% aluminum content
- Air-knife precision: Maintains ±3% coating uniformity
- Post-Treatment Options:
- Code Q (Phosphate+Oiling): 1.5–3.0g/m² oil film (Ra 0.8µm)
- Code S (Sealed Chromate): 0.5µm layer with 85% humidity resistance
Environmental Adaptability
| Exposure Scenario | Recommended Solution | Service Life* |
|---|---|---|
| Coastal bridges | G90 + 75µm fluoropolymer | 30+ years |
| Automotive chassis | G90 + e-coating (20µm) | 15–20 years |
| Grain silos | G90 + 50µm epoxy | 25–30 years |
*Based on ISO 12944-5 corrosion category C5-M
Forming & Fabrication Guide
- Stamping Performance:
- Deep drawing limit: LDR 2.1 (1.5mm sheet)
- Progressive die speed: 45 strokes/min (0.8mm material)
- Welding Parameters:
- Spot welding: 7kA current, 0.3s duration (1.2mm sheets)
- Laser welding: 4kW power at 8m/min (N₂ shielding gas)
- Surface Finishes:
- Zero Spangle: Ra 0.4µm (Suitable for Class A automotive paint)
- Tight Spangle: 50–100µm crystals (Architectural exposed surfaces)
Chemical Composition
| Element | DX51D+G90 | S350GD+G90 | SGCC+G90 |
|---|---|---|---|
| Carbon | ≤0.12% | ≤0.20% | ≤0.15% |
| Manganese | ≤0.60% | ≤1.70% | ≤0.60% |
| Phosphorus | ≤0.025% | ≤0.025% | ≤0.030% |
Low carbon content enables superior weldability (Ceq ≤0.35).
Competitive Advantages
- Corrosion Resistance: 2× better than Z275 in cyclic salt fog tests
- Cost Efficiency: 40% cheaper than 316 stainless steel in C4 environments
- Sustainability: 92% recycled steel content, 97% zinc reclamation rate
Industry Applications
- Construction:
- Solar panel mounting systems (2.0mm G90 withstands 2,500Pa wind loads)
- Prefabricated steel buildings (6.0mm columns with 550MPa tensile strength)
- Transportation:
- Truck trailer floors (3.0mm G90 + diamond plate pattern)
- Railway signal cabinets (1.5mm with IP65-rated seams)
- Energy:
- Wind turbine towers (6.0mm G90 + 200µm polyurethane coating)
- Utility transformer housings (2.3mm with RFI shielding)
Quality Assurance
- Third-party verified coating adhesion: ≤3% loss in 10T bend tests
- Surface defects: ≤2 pinholes/m² (Class I per EN 10169)
- Spangle consistency: 85% uniform crystal distribution
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