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Hot-Dip Galvanized Steel Sheet: The King of Corrosion Resistance in Construction and Industry
Release time:
2025-12-05
Amid the global wave of carbon neutrality and infrastructure development, hot-dip galvanized steel continues to dominate in 2025 thanks to its long lifespan, 100% recyclability, and unmatched cost-performance ratio. Choosing the right zinc coating thickness means choosing peace of mind for the next 20-50 years.
What is Hot-Dip Galvanized Steel?
It is produced by fully immersing cold- or hot-rolled steel sheets into molten zinc at 450-460°C, forming a uniform and strongly bonded zinc-iron alloy layer. This coating serves as both a physical barrier and sacrificial anode, providing superior electrochemical protection even in harsh environments.
Why Hot-Dip Galvanizing Outperforms Regular Steel
- Thick zinc coating: 40-600g/m² (both sides), up to Z1200
- Self-healing: zinc ions react with air at scratches to form dense zinc carbonate, sealing the wound
- Predictable lifespan: each additional 100g/m² extends service life by 8-12 years in atmospheric conditions
2025 Recommended Zinc Coating Grades
- Indoor dry: Z120-Z180 (15-25 years)
- Urban/suburban: Z275 (25-40 years)
- Coastal/heavy industry: Z350-Z600 (40-70+ years)
Typical Applications
- Roofing & cladding: substrate for color-coated steel, corrugated sheets, light-gauge steel framing
- Steel structure plants: purlins, H-beams
- Infrastructure: highway guardrails, lamp posts, solar mounting systems
- Agricultural facilities: greenhouse frames, grain storage silos
Case 1: Shantou Offshore Solar Project (2023-2025) Z450 galvanized brackets 800m from sea: only slight white rust after 30 months, no red rust. Expected lifespan >50 years. Z275 brackets showed heavy red rust in the same period.
Case 2: Inner Mongolia -40°C Cold Storage Z275 + chromium-free passivation air ducts: zero powdering or peeling after 4 winters.
5 Key Points When Purchasing in 2025
- Request third-party zinc coating weight test reports
- Uniform small spangles indicate advanced cooling technology
- Look for continuous galvanizing line marks (e.g., CGCC standard)
- Require chromium-free or trivalent chromium passivation (REACH compliant)
- Ask for Mill Test Certificate (MTC) showing substrate grade DX51D+Z or S350GD+Z
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