What Are Duplex and Super Duplex Stainless Steels?
Duplex stainless steels combine austenitic and ferritic properties — offering superior strength, excellent corrosion resistance, and stress corrosion cracking resistance. Super duplex grades take these properties further with higher alloy content for the most demanding environments.
Chemical Composition Comparison
| Element | Duplex 2205 | Super Duplex 2507 |
|---|---|---|
| Chromium | 21 – 23% | 24 – 26% |
| Nickel | 4.5 – 6.5% | 6.0 – 8.0% |
| Molybdenum | 2.5 – 3.5% | 3.0 – 5.0% |
| Nitrogen | 0.14 – 0.20% | 0.24 – 0.32% |
| PREN Value | 34 – 38 | 40 – 48 |
Mechanical Properties
| Property | Duplex 2205 | Super Duplex 2507 |
|---|---|---|
| Yield Strength | ≥ 450 MPa | ≥ 550 MPa |
| Tensile Strength | ≥ 620 MPa | ≥ 795 MPa |
| Elongation | ≥ 25% | ≥ 15% |
Corrosion Resistance
| Environment | Duplex 2205 | Super Duplex 2507 |
|---|---|---|
| Seawater (general) | Good | Excellent |
| Crevice corrosion | Up to ~30°C | Up to ~50°C |
| Stress corrosion cracking | Excellent | Excellent |
When to Use Duplex 2205
- Chemical processing with moderate chloride content
- Oil and gas production flowlines and manifolds
- Desalination plants (non-critical sections)
- Food and beverage processing equipment
When to Use Super Duplex 2507
- Subsea equipment and pipelines in offshore oil & gas
- Seawater cooling systems and heat exchangers
- Hot chloride environments exceeding 30°C
- Flue gas desulfurization (FGD) systems
Cost Consideration
Super duplex is 30-60% more expensive than Duplex 2205 due to higher alloy content. However, thinner sections and longer service life can offset material costs. Consider total lifecycle cost.
Key Takeaway
Choose Duplex 2205 for general chloride environments. Choose Super Duplex 2507 for hot seawater, aggressive chemicals, or critical subsea applications.
Need Steel Products for Your Project?
CoreMetal Steel (Xi’an Coremetal Steel Co., Ltd.) is a professional steel and metal materials supplier based in Xi’an, China. We export to 60+ countries with ISO 9001 certification. Contact us today for competitive pricing and technical support.
Contact: Tracy | Email: tracy@coremetalsteel.com | Phone: +86 18291910632