Duplex & Super Duplex Stainless Steel
High-strength ferritic-austenitic stainless steels for chloride corrosion, seawater, desalination, offshore, pressure equipment and oil & gas service.
Quick Answer: J&A Alloy supplies super stainless steel products including duplex stainless steel, super duplex stainless steel, super austenitic stainless steel and precipitation-hardening stainless steel in plate, sheet, pipe, tube, bar, wire, forging, flange, fitting and fastener forms for seawater, oil & gas, chemical processing, aerospace, high-strength and chloride corrosion applications.
Use this page to compare super stainless steel families, match grades to chloride resistance, seawater performance, strength or precipitation-hardening requirements, and prepare RFQs with the right product form, standard, heat treatment condition and inspection requirements.
Main Super Stainless Steel Families
Super Austenitic Stainless Steel
High-alloy austenitic grades for sulfuric acid, chloride pitting, seawater, FGD scrubber and chemical processing equipment.
PH Stainless Steel
Precipitation-hardening stainless steels for high strength, aerospace components, shafts, fasteners, springs, diaphragms and precision parts.
Popular Super Stainless Steel Products
| Grade | UNS / Common Name | Best For | Common Product Forms |
|---|---|---|---|
| Duplex Stainless Steel 2205 | UNS S32205 / F51 | General chloride service, heat exchangers, pressure vessels and process piping | Plate, pipe, bar, fittings, flange |
| Duplex Stainless Steel 2507 | UNS S32750 | Seawater, desalination, offshore oil & gas and high-chloride service | Plate, pipe, bar, fittings |
| Duplex Stainless Steel F55 | UNS S32760 | Super duplex pressure equipment, valve, pump, fastener and sour service parts | Bar, forging, flange, fittings |
| Austenitic Stainless Steel 904L | UNS N08904 | Sulfuric acid, phosphoric acid, chemical processing and corrosion-resistant equipment | Plate, sheet, pipe, bar |
| Austenitic Stainless Steel 254SMO | UNS S31254 | Seawater, chloride pitting resistance, heat exchangers and FGD scrubber service | Plate, sheet, pipe, fittings |
| Austenitic Stainless Steel 654SMO | UNS S32654 | Very severe chloride corrosion, seawater and high-alloy stainless applications | Plate, sheet, bar, pipe |
| Stainless Steel 17-4PH | UNS S17400 | High-strength shafts, valves, aerospace parts, fasteners and structural components | Bar, plate, forging, wire |
| Stainless Steel 17-7PH | UNS S17700 | Springs, diaphragms, bellows, washers and aerospace precision components | Sheet, strip, wire, bar |
Duplex Stainless Steel 2205 vs 2507 vs F55
| Grade | Relative Strength / Corrosion Resistance | Typical Applications | Selection Notes |
|---|---|---|---|
| 2205 / UNS S32205 | Strong balance of strength and corrosion resistance | Chemical tanks, pressure vessels, heat exchangers and process piping | Cost-effective starting point when 316L is not enough. |
| 2507 / UNS S32750 | Higher chloride pitting and seawater resistance than 2205 | Seawater piping, desalination, offshore platforms and high-chloride equipment | Use when chloride level or seawater exposure is more severe. |
| F55 / UNS S32760 | Super duplex strength with strong pitting and crevice corrosion resistance | Pumps, valves, fasteners, flanges, forged parts and sour service components | Often specified for forged or pressure-containing components. |
904L vs 254SMO vs 654SMO
Super austenitic stainless steels are often selected when a fully austenitic structure, high corrosion resistance and good fabrication performance are required.
| Grade | Best Starting Use | Why | Procurement Notes |
|---|---|---|---|
| 904L / UNS N08904 | Sulfuric acid, phosphoric acid and chemical process equipment | High nickel and molybdenum improve acid corrosion resistance. | Confirm acid concentration, temperature and plate/sheet/pipe standard. |
| 254SMO / UNS S31254 | Seawater, chloride-rich process streams and FGD scrubbers | High molybdenum and nitrogen improve pitting and crevice corrosion resistance. | Confirm chloride level, welding requirement and inspection. |
| 654SMO / UNS S32654 | Very severe chloride corrosion where 254SMO may not be enough | Very high alloy content supports stronger chloride and seawater resistance. | Confirm availability, lead time and whether nickel alloy is a better option. |
PH Stainless Steel Selection Guide
| If your project needs... | Start with... | Why |
|---|---|---|
| General high strength with good corrosion resistance | 17-4PH, 15-5PH | Common precipitation-hardening stainless grades for shafts, valves, aerospace and structural parts. |
| Spring, diaphragm or bellows performance | 17-7PH, 15-7Mo | Semi-austenitic PH grades are widely used where spring properties and fatigue resistance matter. |
| High toughness and aerospace fastener performance | PH13-8Mo, 15-5PH | Good combination of strength, toughness and corrosion resistance for critical parts. |
| Custom high-strength stainless component | Custom 450, 17-4PH | Used where high strength, corrosion resistance and custom processing are required. |
Choose by Application
| Application | Recommended Starting Grades | Selection Notes |
|---|---|---|
| Marine and seawater service | 2507, F55, 254SMO, 654SMO | Review chloride level, temperature, flow, crevice risk and welding requirements. |
| Chemical processing and acid service | 904L, 254SMO, 2205, 2507 | Confirm acid concentration, temperature, oxidizing/reducing conditions and impurities. |
| Oil & gas and sour service | 2507, F55, 2205, 17-4PH | Confirm NACE/MR0175 or project specification, strength level and corrosion environment. |
| Aerospace and precision components | 17-4PH, 15-5PH, 17-7PH, PH13-8Mo | Heat treatment condition, mechanical properties and traceability are critical. |
| Springs, diaphragms and bellows | 17-7PH, 15-7Mo | Specify strip/wire condition, temper, fatigue, flatness and surface finish. |
| FGD scrubbers and chloride process water | 254SMO, 654SMO, 2507 | Consider pitting resistance, crevice corrosion and weld procedure. |
Available Product Forms
| Product Form | Typical Grades | RFQ Information to Confirm |
|---|---|---|
| Plate / Sheet / Strip | 904L, 254SMO, 654SMO, 2205, 2507, 17-7PH | Thickness, width, length, surface, flatness, cutting and tolerance. |
| Pipe / Tube | 2205, 2507, F55, 904L, 254SMO | Seamless/welded type, OD, wall thickness, schedule, length and standard. |
| Bar / Rod | 17-4PH, 15-5PH, PH13-8Mo, 2205, 2507, F55 | Diameter, length, heat treatment condition, tolerance and mechanical properties. |
| Forging / Flange / Fittings | F55, 2507, 2205, 17-4PH, 15-5PH | Drawing, pressure class, forging condition, heat treatment and inspection. |
| Wire / Fasteners / Precision Parts | 17-7PH, 15-7Mo, 17-4PH, 15-5PH | Diameter, temper, tensile strength, spring requirement and surface finish. |
Common Standards and Procurement Notes
| Requirement | What to Specify | Why It Matters |
|---|---|---|
| Standard / specification | ASTM, ASME, EN, NORSOK, NACE, AMS or customer drawing | Super stainless steels are often used in corrosion-critical and strength-critical projects. |
| Heat treatment condition | Solution annealed, age hardened, H900/H1025/H1150 or project condition | PH stainless steel properties depend strongly on heat treatment condition. |
| Corrosion environment | Chloride level, seawater exposure, acid concentration, pH, temperature and crevice risk | Correct alloy selection depends on the actual medium and service temperature. |
| Inspection | EN 10204 3.1 MTC, PMI, UT, tensile, hardness, ferrite, corrosion test or third-party inspection | Traceability and verified properties are important for pressure, offshore and aerospace service. |
PREN / Corrosion Resistance Selection Guide
For chloride service, buyers often compare super stainless steel grades by pitting resistance, seawater exposure and crevice corrosion risk. PREN is a useful first screening value, but final selection should also consider temperature, pH, deposits, welding, pressure and project standards.
| Service Condition | Recommended Starting Grades | Why | Key Checks |
|---|---|---|---|
| General chloride service above 316L capability | Duplex 2205, 904L | Better strength and chloride resistance than common austenitic stainless steels. | Chloride level, temperature, pH and welding procedure. |
| Seawater and desalination service | Super Duplex 2507, F55, 254SMO | Higher pitting and crevice corrosion resistance for chloride-rich environments. | Crevice design, flow rate, stagnant zones and inspection plan. |
| FGD scrubber and chloride process water | 254SMO, 654SMO, 2507 | High molybdenum and nitrogen content improve resistance to localized corrosion. | Chloride concentration, pH, temperature and welding consumables. |
| Very severe chloride corrosion | 654SMO, selected nickel alloys | Very high alloy content may be required where 254SMO or 2507 is not enough. | Compare availability, cost, lead time and whether Hastelloy/Inconel is more suitable. |
| Sour service / offshore components | 2507, F55, 17-4PH where allowed | Super duplex grades combine strength and chloride resistance for many offshore parts. | NACE/MR0175, hardness limits, heat treatment and project approval. |
17-4PH vs 15-5PH vs 17-7PH vs PH13-8Mo
PH stainless steels are selected when high strength, hardness, spring performance or precision mechanical properties are required. The right grade depends on strength level, toughness, corrosion resistance, product form and heat treatment condition.
| Grade | Best Starting Use | Typical Forms | Selection Notes |
|---|---|---|---|
| 17-4PH / UNS S17400 | Shafts, valve parts, pump components, aerospace hardware and high-strength structural parts | Bar, plate, forging, wire | Common and versatile PH stainless grade; specify H900, H1025, H1150 or required condition. |
| 15-5PH / UNS S15500 | Aerospace parts, fasteners, fittings and components needing improved toughness | Bar, forging, plate | Often considered where toughness and transverse properties are important. |
| 17-7PH / UNS S17700 | Springs, diaphragms, bellows, washers, clips and precision strip components | Sheet, strip, wire, bar | Useful for spring properties, fatigue resistance and formed precision parts. |
| 15-7Mo / UNS S15700 | High-strength springs, diaphragms and aerospace strip applications | Sheet, strip, wire | Molybdenum-bearing semi-austenitic PH grade for strength and fatigue-related applications. |
| PH13-8Mo / UNS S13800 | Aerospace fasteners, shafts, landing gear parts and high-toughness components | Bar, forging, plate | Good combination of strength, toughness and stress corrosion resistance in controlled conditions. |
Super Stainless Steel vs Nickel Alloy
Super stainless steels can be a cost-effective upgrade from standard stainless steel, but some environments require nickel alloys such as Inconel, Hastelloy, Incoloy, Monel or commercially pure nickel. Use this comparison as a first selection path before final engineering review.
| Use Super Stainless Steel When... | Consider Nickel Alloy When... |
|---|---|
| The main problem is chloride pitting, seawater or higher strength than 316L. | The service involves severe mixed acids, reducing acids, wet chlorine or very aggressive chemical media. |
| Duplex or super duplex strength and corrosion resistance meet the project specification. | The project requires stronger resistance from Hastelloy C-276, C-22, Inconel 625, Incoloy 825 or Monel 400. |
| The component can be fabricated and welded within duplex/super austenitic stainless guidelines. | The environment includes high-temperature corrosion, caustic alkali, hydrofluoric acid or critical chemical equipment. |
| Cost, availability and mechanical strength make 2205, 2507, F55, 254SMO or 904L practical. | Failure risk, downtime cost or corrosion data justify upgrading to a nickel alloy family. |
Related Material Selection Links
Use these links to compare stainless steel families, nickel alloys and corrosion resistant alloys before sending an RFQ.
Super Stainless Steel FAQ
What is super stainless steel?
Super stainless steel refers to stainless grades with higher alloy content, strength or corrosion resistance than standard stainless steels, including duplex, super duplex, super austenitic and precipitation-hardening stainless steels.
When should I choose 2507 instead of 2205?
Choose 2507 when chloride level, seawater exposure or pitting resistance requirements are more severe than 2205 can handle, subject to project specifications and engineering review.
What is 254SMO used for?
254SMO is commonly used for seawater, chloride-rich process streams, FGD scrubbers, heat exchangers and chemical processing equipment requiring strong pitting resistance.
What is the difference between 17-4PH and 17-7PH?
17-4PH is a common high-strength PH stainless steel for shafts, valves and structural components, while 17-7PH is often selected for springs, diaphragms, bellows and precision strip or wire parts.
What information is needed for a quote?
Please send grade, UNS number, product form, size, quantity, standard, heat treatment condition, inspection requirement, service medium and destination country.
Can J&A Alloy supply custom super stainless steel sizes?
Yes. J&A Alloy can quote standard and custom sizes for plate, sheet, pipe, tube, bar, wire, forging, flange, fitting, fastener and precision processed forms.
Request a Super Stainless Steel Quote
Send us the grade, UNS number, product form, size, quantity, standard, heat treatment condition, inspection requirement, service medium and destination country. If you are comparing grades, include chloride level, temperature, pressure, pH, load and fabrication requirements.
- Material: grade, UNS number or equivalent specification
- Form and size: plate, sheet, pipe, tube, bar, wire, forging, flange, fitting or fastener
- Condition: solution annealed, age hardened, H900/H1025/H1150 or project condition
- Inspection: EN 10204 3.1 MTC, PMI, UT, tensile, hardness, ferrite, third-party inspection