SPA‑H and SPA‑C are both weathering steels, but SPA‑H has significantly higher and more complete alloying - especially in Cr, Cu, P, and most importantly Ni - which directly gives it better corrosion resistance and patina stability.
1. Key difference in alloy system
SPA‑C:Basic weathering composition: Cu + Cr + PNo nickel (Ni) or only trace Ni.
SPA‑H:High‑performance weathering system: Cu + Cr + P + NiNickel is the biggest differentiator.
2. Typical composition comparison
| Element | SPA‑C (container grade) | SPA‑H (high weather resistance) | Role |
|---|---|---|---|
| Cu | Lower | Higher | Improves adhesion & density of patina |
| Cr | Lower | Higher | Enhances corrosion stability |
| P | Moderate | Higher | Accelerates patina formation |
| Ni | Almost none | Clearly added | Improves toughness & corrosion in harsh environments |
| C | Low | Low | Ensures weldability |
3. Why this difference matters
SPA‑C:Lower alloy = lower cost, good enough for containers & general structures.
SPA‑H:Higher alloy + Ni = much denser, more stable patina →suitable for buildings, bridges, landscapes, long‑life outdoor structures.
