Q345GNH is a high‑performance Chinese weathering steel with excellent atmospheric corrosion resistance, generally better than standard Q345NH and comparable to ASTM A588 / Corten‑A, but inferior to high‑Ni marine‑grade weathering steels.
1. Core alloying & performance basis
Alloy system: Cu + P + Cr + Ni (higher Cr/Ni than Q345NH)
Patina: Forms a dense, protective patina ~2–5× slower corrosion than ordinary carbon steel
Typical use: General outdoor structures, signage, bridges, containers
2. Direct comparison with other weathering steels
A. Domestic Chinese grades
| Grade | Weathering resistance vs Q345GNH | Key difference |
|---|---|---|
| Q345NH | Inferior | Lower Cr/Ni; less stable patina; poorer in industrial/coastal zones |
| Q345GNHL | Similar or slightly better | Optimized for low‑temperature toughness; same corrosion resistance |
| Q355GNH | Slightly better | Higher strength; similar or marginally improved corrosion resistance |
| Q345qENH / Q345qDNHY‑I | Superior | Higher Ni (0.8–1.2%); much better chloride resistance (marine) |
| SPA‑H (Japanese) | Comparable | Similar Cu‑Cr‑Ni system; nearly equivalent atmospheric resistance |
B. International grades
| Grade | Weathering resistance vs Q345GNH | Notes |
|---|---|---|
| ASTM A588 (Corten‑A) | Very close / Equivalent | Same corrosion category; minor compositional differences; patina behavior nearly identical |
| S355J0WP / S355J2WP (EN) | Comparable | European equivalent; similar performance |
| High‑Ni marine grades (e.g., 1Ni‑series) | Significantly superior | Ni ≥ 0.8%; designed for coastal/salty environments; 5–10× better than plain carbon steel |
3. Summary of relative performance
Better than: Q345NH, Q235NH, ordinary carbon steel (Q235, Q345B)
Equal to: ASTM A588, SPA‑H, Q355GNH, Q345GNHL
Worse than: High‑nickel marine weathering steels (Q345qDNHY‑I, 09CuPCrNi‑A with high Ni)
