Hot Dip Galvanized Coil: Superior Corrosion Resistance with ASTM-Compliant Zinc Protection
Hot Dip Galvanized Coil Product Overview
Hot Dip Galvanized Coil is a carbon steel substrate coated with a zinc alloy layer (99.9% pure Zn) through a high-temperature immersion process (445–465°C). This method creates a metallurgical bond between the steel and zinc, delivering 50–100 years of corrosion resistance in moderate environments. Ideal for automotive panels, structural beams, and agricultural equipment, it meets ASTM A653, EN 10346, and JIS G3302 standards. With zinc coatings ranging from 60–275 g/m² (8–80 μm), it outperforms electrogalvanized steel by 3–5x in lifespan while offering self-healing scratch protection.
Key Technical Specifications
1. Dimensional & Coating Properties
- Thickness: 0.12–3.5 mm (±5% tolerance per ASTM A924)
- Width: 600–1,500 mm (custom slitting for automotive stamping)
- Coating Weight:
- Standard (Z12): 120 g/m² (17 μm) for indoor appliances
- Heavy-Duty (Z27): 270 g/m² (38 μm) for coastal infrastructure
- Surface Finish:
- Zero Spangle (Z): Smooth, spangle-free for painting (Ra ≤0.8 μm)
- Minimized Spangle (M): Fine crystalline texture (Ra 1.2–2.5 μm)
- Normal/Large Spangle: Decorative for non-critical applications
2. Chemical Composition
| Grade (EN 10346) | C (%) | Si (%) | Mn (%) | P (%) | S (%) |
|---|---|---|---|---|---|
| DX51D+Z | ≤0.12 | ≤0.50 | ≤0.60 | ≤0.10 | ≤0.045 |
| S350GD+Z | ≤0.20 | ≤0.60 | ≤0.70 | ≤0.10 | ≤0.045 |
| S550GD+Z | ≤0.20 | ≤0.60 | ≤0.70 | ≤0.10 | ≤0.045 |
Key Alloy Benefits:
- Zinc Purity: ≥99.9% for uniform coating adhesion.
- Trace Elements: Controlled Al (0.15–0.22%) to minimize dross.
Mechanical Performance
| Grade | Yield Strength (MPa) | Tensile Strength (MPa) | Elongation (%) |
|---|---|---|---|
| DX51D+Z | 240–380 | 270–500 | ≥22 |
| S250GD+Z | ≥250 | ≥330 | ≥19 |
| S550GD+Z | ≥550 | ≥550 | – |
Functional Metrics:
- Bendability: 0T–2T (180° bend @ 0.8 mm thickness).
- Weldability: 10–15 kA spot welding current (20% lower than bare steel).
- Impact Resistance: 40 J/cm² at -20°C (ISO 148-1).
Corrosion Resistance & Environmental Adaptability
- Salt Spray Performance:
- Z12 (120 g/m²): 1,200 hours to red rust (ASTM B117).
- Z27 (270 g/m²): 2,500+ hours in marine zones (ISO 9227).
- Self-Healing Mechanism: Zinc sacrificially corrodes at 0.05–0.15 mm/year to protect exposed edges.
- Temperature Tolerance:
- Continuous Use: -40°C to 200°C.
- Peak Temp: 315°C (short-term exposure).
Applications by Industry
| Industry | Use Case | Recommended Coating |
|---|---|---|
| Construction | Structural beams, roofing | S350GD+Z (Z27 coating) |
| Automotive | Chassis, exhaust shields | DX54D+Z (Z18 coating) |
| Agriculture | Grain silos, livestock fencing | S220GD+Z (Z20 coating) |
| Energy | Solar mounting systems | S550GD+Z (Z15 coating) |
Production Process
- Material Prep:
- Degreasing (NaOH solution) → Pickling (HCl, 10–15%) → Fluxing (ZnCl₂-NH₄Cl).
- Galvanizing:
- Immersion in molten zinc (445°C) → Air-knife coating control (±3 g/m²).
- Post-Treatment:
- Passivation (Cr-free, hexavalent chromium alternatives) → Oiling (anti-fingerprint).
Global Standard Equivalents
| China (GB) | Europe (EN) | USA (ASTM) | Japan (JIS) |
|---|---|---|---|
| DC51D+Z | DX51D+Z | A653 CS Type B | SGCC |
| S350GD+Z | S350GD+Z | A653 SS345 | SGHC340 |
| S550GD+Z | S550GD+Z | A653 SS550 | SGHC550 |
Sustainability & Certifications
- Recycled Content: 25–35% (ISO 14021 compliant).
- Carbon Footprint: ≤1.3 tons CO₂ per ton of steel.
- Certifications: RoHS, REACH, LEED v4.1.
Packing And Delivery
