1. Regional Standardization & Naming Conventions
SPA-H: Complies with Japanese Industrial Standards (JIS G 3125)-the primary weathering steel grade in Japan and widely used in Asian markets (China, South Korea).
Corten A/Corten B (ASTM A242/A588): Complies with American Society for Testing and Materials (ASTM) standards-Corten A is for general structural use, Corten B/A588 have higher strength; dominant in North America, Europe, and global projects.
Q355NH/Q235NH: Complies with Chinese National Standards (GB/T 4171)-Q355NH is the high-strength variant (equivalent to A588/SPA-H), Q235NH is the low-strength variant; the main weathering steel grades in China's domestic market.
S355J2W/S235J2W: Complies with European Standards (EN 10025-5)-Europe's primary weathering steel grades, with S355J2W matching the strength of SPA-H/A588.
2. Chemical Composition: Minor Variations in Alloy Ranges
Copper (Cu): SPA-H specifies 0.20–0.50% Cu (same as Corten A/A588), while Q355NH allows a slightly wider range (0.20–0.60%) and S355J2W requires a minimum of 0.25%.
Chromium (Cr): SPA-H has a Cr range of 0.30–1.25%, which is broader than Corten A (0.40–1.00%) and aligns with Q355NH (0.30–1.20%).
Phosphorus (P): SPA-H allows 0.07–0.15% P (a key element for uniform patina), which is similar to Corten A (0.06–0.15%) but higher than Q355NH's upper limit of 0.12%.
Nickel (Ni): SPA-H includes a small Ni range (0.20–0.50%) for enhanced coastal corrosion resistance, while Corten A has no mandatory Ni requirement (only optional trace amounts).
3. Mechanical Properties: Strength & Ductility
Yield Strength: SPA-H has a minimum yield strength of 345 MPa (50 ksi), matching A588 (345 MPa) and Q355NH (355 MPa), and significantly higher than Corten A (248 MPa) and S235J2W (235 MPa).
Tensile Strength: SPA-H ranges from 480–620 MPa, comparable to A588 (485–655 MPa) and Q355NH (470–630 MPa).
Ductility: SPA-H has an elongation at break of ≥20%, similar to other high-strength weathering steels, ensuring good formability for bending/curving applications (e.g., facades, sculptures).
4. Application Focus & Market Adoption
SPA-H: Dominant in Japanese and Asian construction/industrial projects-used for architectural facades, sculptures, signage, bridge railings, and outdoor industrial equipment in East Asia's urban/coastal environments.
Corten A/A588: Preferred in North America, Europe, and global international projects-the "Corten" brand is widely recognized for architectural applications (e.g., iconic buildings, public art).
Q355NH/Q235NH: The de facto choice for China's domestic market-used in all local weathering steel applications, from municipal street furniture to large-scale bridge structures.
S355J2W/S235J2W: The primary grade for European construction and infrastructure projects, with strict compliance to EU environmental and structural standards.
5. Patina Formation & Environmental Adaptability
SPA-H: Forms a dense, uniform reddish-brown patina in 6–12 months (similar to A588/Q355NH), with good resistance to mild coastal salt spray (≤5 km from the ocean) thanks to its Ni content.
Corten A: Patina forms slightly slower (8–12 months) in dry environments, with excellent performance in urban/industrial pollution.
Q355NH: Patina formation speed aligns with SPA-H, optimized for China's diverse climatic conditions (high humidity in the south, dryness in the north).
