Corten B, also known as Weathering Steel Grade B and specified under ASTM A588 Grade B, is a high-strength low-alloy (HSLA) steel engineered to withstand long-term atmospheric exposure without protective coatings.
Through controlled additions of copper, chromium, nickel, and phosphorus, Corten B forms a dense, adherent oxide layer (patina) that significantly slows corrosion. This provides approximately 5–8× higher atmospheric corrosion resistance than conventional carbon steel.
Corten B is optimized for structural strength and durability, making it ideal for bridges, heavy construction, infrastructure, and transportation systems.
Chemical Composition
| Element | Typical Range | Function |
|---|---|---|
| Carbon (C) | ≤ 0.19 | Strength |
| Copper (Cu) | 0.20 – 0.40 | Corrosion resistance |
| Chromium (Cr) | 0.40 – 0.65 | Oxide layer stability |
| Nickel (Ni) | ≤ 0.40 | Toughness |
| Phosphorus (P) | ≤ 0.04 | Patina formation |
| Manganese (Mn) | 0.80 – 1.25 | Strength |
| Silicon (Si) | ≤ 0.40 | Strength |
| Iron (Fe) | Balance | Base metal |
Key Characteristics
Superior Atmospheric Corrosion Resistance
• Natural patina protects against further corrosion
• Suitable for unpainted outdoor exposure
High Structural Strength
• Higher yield and tensile strength than Corten A
• Ideal for bridges and heavy load-bearing structures
Low Maintenance & Long Service Life
• Eliminates repainting cycles
• Reduces total lifecycle cost
Good Weldability & Fabrication
• Weldable using standard low-hydrogen electrodes
• Suitable for cutting, bending, and forming
Industrial-Grade Durability
• Performs well in urban and industrial atmospheres
• Resistant to fatigue and vibration loading
Metallurgical & Heat Treatment Features
• Supplied in hot-rolled condition
• Ferritic–pearlitic microstructure
• Not intended for quenching and tempering
• Strength achieved through alloying and controlled rolling
Welding & Fabrication Guidelines
Welding
• Use weathering-steel-compatible filler metals
• Preheating generally not required for thin sections
• Clean weld zones to ensure uniform patina development
Forming & Machining
• Good cold-forming characteristics
• Machinability similar to structural carbon steel
Available Forms
✔ Hot-rolled plates & sheets
✔ Coils
✔ Structural sections (I, H, channels, angles)
✔ Flats, rounds & bars
✔ Pipes & tubes (seamless & welded)
✔ Prefabricated structural components
Standards & Equivalents
| Standard | Grade |
|---|---|
| ASTM | A588 Grade B |
| EN | S355J2W |
| JIS | SPA-H |
| DIN | Weathering steel equivalent |
Applications
Construction & Infrastructure: Bridges, flyovers, towers, railway wagons
Architectural: Facades, outdoor structures, sculptures, panels
Industrial: Storage tanks, machinery frames, plant structures
Marine & Coastal (Non-Submerged): Harborside structures, coastal installations
Corten B vs Corten A
| Feature | Corten A | Corten B |
|---|---|---|
| Strength | Moderate | Higher |
| Corrosion Resistance | Excellent | Excellent |
| Architectural Finish | Superior | Good |
| Structural Use | Moderate loads | Heavy loads |
| Typical Applications | Facades, art | Bridges, structures |
Advantages
✔ No painting required
✔ High load-bearing capacity
✔ Excellent corrosion resistance
✔ Long service life
✔ Reduced maintenance costs
✔ Environmentally sustainable
Limitations & Design Considerations
⚠ Not suitable for permanent wet or submerged conditions
⚠ Initial rust runoff may stain adjacent materials
⚠ Proper drainage detailing required
⚠ Coastal environments may need additional protection
Why Choose Corten B
Corten B weathering steel combines superior structural strength with long-term corrosion resistance. Its ability to form a protective patina and operate with minimal maintenance makes it the preferred choice for bridges, infrastructure, industrial frameworks, and heavy construction projects designed for decades of service life.