Corten A is a high-strength, low-alloy (HSLA) weathering steel designed to provide superior resistance to atmospheric corrosion. It conforms primarily to EN 10025-5 S355J0WP and ASTM A242 Type 1 standards.
The steel contains controlled additions of copper, chromium, nickel, and phosphorus, which enable the formation of a dense, adherent oxide layer (patina). This natural patina seals the surface and dramatically slows further corrosion, eliminating the need for painting in many outdoor environments.
Chemical Composition
| Element | % | Contribution |
|---|---|---|
| Carbon (C) | ≤ 0.12 | Strength |
| Copper (Cu) | 0.25 – 0.55 | Corrosion resistance |
| Chromium (Cr) | 0.50 – 1.25 | Oxide layer stability |
| Nickel (Ni) | ≤ 0.65 | Toughness & corrosion resistance |
| Phosphorus (P) | 0.07 – 0.15 | Patina formation |
| Manganese (Mn) | ≤ 1.20 | Strength |
| Silicon (Si) | 0.25 – 0.75 | Strength |
| Iron (Fe) | Balance | Base metal |
Corrosion Mechanism
• Initial exposure forms surface rust
• Alloying elements cause rust to densify and adhere
• Oxygen and moisture penetration slows dramatically
• Corrosion rate decreases exponentially over time
• Final patina color ranges from orange-brown to dark bronze
Atmospheric corrosion resistance: Approximately 4–8 times higher than conventional carbon steel in suitable environments.
Mechanical Properties
| Property | Typical Value |
|---|---|
| Yield Strength | ≥ 355 MPa |
| Tensile Strength | 470 – 630 MPa |
| Elongation | 20 – 25% |
| Hardness | 170 – 200 HB |
| Impact Toughness | Good at low temperatures |
| Density | 7.85 g/cm³ |
| Modulus of Elasticity | ~210 GPa |
Key Characteristics
Exceptional Atmospheric Corrosion Resistance
• Self-healing oxide layer
• No painting required in most outdoor environments
High Structural Strength
• Suitable for load-bearing applications
• Comparable to S355 structural steel
Excellent Weldability & Fabrication
• Weldable with weathering-steel-compatible fillers
• Good formability for bending and rolling
Low Maintenance & Long Service Life
• Reduced repainting and inspection costs
• Ideal for lifecycle-cost-driven projects
Distinct Architectural Appearance
• Natural evolving patina
• Highly valued in contemporary design
Heat Treatment & Metallurgy
• Supplied in hot rolled condition
• Not intended for quenching and tempering
• Controlled rolling optimizes grain structure
• Stable ferritic–pearlitic microstructure
Welding & Fabrication
• Excellent weldability with matching fillers
• Preheating generally not required for thin sections
• Post-weld cleaning ensures uniform patina development
• Machinability similar to structural carbon steel
Available Forms
✔ Hot rolled plates
✔ Sheets & coils
✔ Cold rolled sheets
✔ Structural sections (beams, channels, angles)
✔ Flats, rounds & hollow sections
✔ Decorative panels & CNC-cut components
Standards & Equivalents
| Standard | Grade |
|---|---|
| EN 10025-5 | S355J0WP |
| ASTM | A242 Type 1 |
| ASTM | A588 (similar) |
| JIS | SPA-H |
| DIN | Weathering steel equivalent |
Applications
Architecture: Facades, cladding, louvers, staircases
Infrastructure: Bridges, flyovers, noise barriers
Industrial: Tanks, chimneys, structural frames
Urban Design: Sculptures, planters, outdoor furniture
Marine (Urban): Harborside structures (not submerged)
Corten A vs Mild Steel
| Feature | Corten A | Mild Steel |
|---|---|---|
| Corrosion Resistance | Very high | Low |
| Maintenance | Minimal | High |
| Aesthetic Value | High | Low |
| Lifespan | Long | Short |
| Lifecycle Cost | Lower | Higher |
Advantages
✔ No painting required
✔ Long service life
✔ Reduced maintenance cost
✔ Environmentally sustainable
✔ Strong aesthetic identity
Limitations & Design Notes
⚠ Not suitable for permanently wet or submerged conditions
⚠ Runoff staining during early patina formation
⚠ Proper drainage design required
⚠ Coastal environments may need additional protection
Why Choose Corten A
Corten A combines structural strength, corrosion resistance, sustainability, and architectural beauty. Its self-protecting patina makes it an ideal choice for long-life outdoor structures where low maintenance and strong visual impact are critical.