Exceptional Corrosion Resistance and Strength of F53 (UNS S32750) Super Duplex Stainless Steel
F53 (UNS S32750) is a super duplex stainless steel known for its exceptionally high strength, excellent resistance to pitting, crevice, and stress corrosion cracking, and outstanding performance in harsh chloride-containing environments. It is widely used in offshore platforms, chemical processing, desalination, and power generation.
This article will introduce the chemical composition, performance, standards and applications of F53 to help you choose the right material for extreme conditions.
What is F53 Stainless Steel?
F53, also known as Super Duplex 2507 or UNS S32750, is a 50/50 austenite-ferrite microstructure stainless steel designed to handle highly corrosive environments. It combines double the strength of austenitic grades with superior resistance to chloride stress corrosion and localized attack.
F53 is ideal for aggressive applications involving seawater, brine, and sour gas (H₂S), and offers excellent mechanical properties and weldability.
F53 Equivalent Grades
| Standard / System | Equivalent Designation |
| UNS | S32750 |
| ASTM / ASME | ASTM A182 F53 / A479 / A276 / A240 |
| EN / DIN | 1.4410 (X2CrNiMoN25-7-4) |
| AFNOR | Z3CN25-06Az |
| ISO | X2CrNiMoN25-7-4 |
F53 Chemical Composition
| Element | Content (%) |
| Chromium (Cr) | 24.0 – 26.0 |
| Nickel (Ni) | 6.0 – 8.0 |
| Molybdenum (Mo) | 3.0 – 5.0 |
| Nitrogen (N) | 0.24 – 0.35 |
| Carbon (C) | ≤ 0.030 |
| Manganese (Mn) | ≤ 1.2 |
| Silicon (Si) | ≤ 0.80 |
| Phosphorus (P) | ≤ 0.035 |
| Sulfur (S) | ≤ 0.020 |
| Iron (Fe) | Balance |
F53 Mechanical Properties
| Property | Typical Value |
| Tensile Strength | ≥ 795 MPa |
| Yield Strength | ≥ 550 MPa |
| Elongation | ≥ 15% |
| Hardness (HBW) | ≤ 310 |
| Impact Toughness | Excellent down to -50 °C |
F53 Physical Properties
| Property | Value |
| Density | 7.8 g/cm³ |
| Melting Point | ~1350 °C |
| Thermal Conductivity | ~14 W/m·K |
| Electrical Resistivity | ~0.8 µΩ·m |
| Modulus of Elasticity | ~200 GPa |
| PREN (Pitting Index) | >40 |
Applications of F53 Stainless Steel
- Offshore Oil & Gas: Subsea piping, risers, manifolds, seawater injection systems.
- Desalination Plants: High-pressure piping, brine outlets, evaporators.
- Chemical Processing: Acid-handling vessels, heat exchangers, and reactors.
- Pulp & Paper: Bleaching equipment, digester components.
- Power Generation: Condensers, flue gas desulfurization units.
Advantages of F53
- Superior corrosion resistance in seawater, chlorides, and acidic media.
- Double the strength of 300-series stainless steels, reducing wall thickness.
- Excellent stress corrosion cracking resistance in chlorides and sour service.
- High mechanical strength even at elevated temperatures.
- Good weldability when properly controlled.
Limitations of F53
- High cost compared to standard stainless grades.
- Sensitive to heat input during welding; requires controlled interpass temperatures.
- May experience reduced impact toughness in very thick sections without proper heat treatment.
- Not suitable for high-temperature (>300 °C) service due to phase instability.
F53 vs Other Stainless Steels
| Feature | 316L | 2205 (F51) | F53 (2507) |
| PREN | ~25 | ~35 | > 40 |
| Tensile Strength (MPa) | ~530 | ~620 | ~795 |
| Chloride Resistance | Moderate | High | Very High |
| Cost | Low | Medium | High |
| Weldability | Excellent | Good | Good (with control) |
Summary
F53 (UNS S32750) is a super duplex stainless steel built for extreme environments requiring high strength, resistance to pitting and stress corrosion, and long service life in aggressive media. Its performance far exceeds conventional stainless steels and even standard duplex grades like F51.
MT.BOLTS supplies F53 fasteners, bars, flanges, and fittings for use in marine, offshore, and chemical industries. Contact us for a technical consultation or request a quote tailored to your application.
