Home > Seamless Tube > ASTM A789 / ASTM A790
Inox Steel India supplies ASTM A789 and ASTM A790 Duplex & Super Duplex Tubes in grades S31803, S32205, S32750, and S32760, designed for extreme-strength and high-corrosion environments. With a dual-phase ferritic–austenitic microstructure, these tubes offer 2X the strength of austenitic stainless steels and outstanding resistance to pitting, crevice corrosion, stress corrosion cracking (SCC) and chloride-rich media.
ASTM A789 covers seamless and welded duplex stainless steel tubing, while ASTM A790 covers seamless and welded pipe products in the same metallurgy. Together, they support critical operations in offshore rigs, subsea pipelines, desalination plants, heat exchangers, chemical process equipment, and firewater systems.
✔ Grades Offered
These tubes are processed through cold drawing, solution annealing, water quenching, ferrite control, PMI testing and NDT validation to ensure optimal performance under severe temperature and corrosive conditions.
Our ASTM A789 / A790 tubes are trusted by:
Inox Steel India supplies Duplex & Super Duplex tubing across India, GCC, Europe, Africa, South East Asia & North America — backed by full certification and export-grade protection.
| Parameter | ASTM A789 / ASTM A790 Duplex & Super Duplex Tubes |
|---|---|
| Standards | ASTM A789 – Seamless & Welded Ferritic/Austenitic Stainless Steel Tubing • ASTM A790 – Seamless & Welded Duplex/Super Duplex Stainless Steel Pipe |
| Grades (Duplex) | UNS S31803, UNS S32205 (Duplex 2205) |
| Grades (Super Duplex) | UNS S32750, UNS S32760 (Super Duplex 2507) |
| Material Structure | Ferritic–Austenitic (Dual-phase microstructure) |
| Manufacturing Process | Seamless • Welded • Cold Drawn • Solution Annealed |
| Size Range (OD) | 6 mm to 508 mm |
| Thickness (WT) | 0.5 mm to 30 mm |
| Length Options | 6m • 12m • Custom cut lengths |
| Surface Finishes | Annealed & Pickled (AP) • Mechanical Polish • Bead-removed Welded Finish |
| Corrosion Resistance | Excellent resistance to pitting, SCC, chlorides & seawater environments |
| Mechanical Strength | Very high — Yield: 450–550 MPa (Duplex), 550–650 MPa (Super Duplex) |
| Heat Treatment | Solution Annealed + Water Quench |
| End Finish | Plain Ends • Beveled Ends • Custom Machined Ends |
| Testing (Mandatory) | Hydrostatic • NDT (UT/EC) • Tensile • Hardness • Flattening • Flaring |
| Special Testing | PMI • Ferrite Content Check • Pitting Resistance (PREN) • IGC • Surface Roughness |
| Ferrite Range | 30–70% (as per ASTM requirements) |
| Documentation | MTC EN 10204 3.1 • Chemical & Mechanical Reports • NDT Reports |
| Key Advantages | High chloride resistance • High mechanical strength • Excellent weldability • Long service life |
| Typical Applications | Offshore platforms • Subsea equipment • Heat exchangers • Petrochemicals • Desalination • Chemical processing equipment • Pulp & paper • Firefighting & utility lines in marine environments |
ASTM A789 & A790 tubing is engineered for high-pressure, high-corrosion, and chloride-rich environments. The dual-phase microstructure provides exceptional strength, toughness, pitting resistance, and SCC resistance, making these tubes ideal for offshore, marine, chemical, and thermal applications.
🔹 1. Offshore & Subsea Systems
Designed for continuous exposure to seawater, high chlorides & mechanical stress.
Applications:
Best Grades: S32205 • S32750 • S32760
🔹 2. Desalination & RO Plants
Exceptional pitting resistance (high PREN values) makes these tubes ideal for saline environments.
Used For:
Recommended: Super Duplex 2507 (S32750/S32760)
🔹 3. Heat Exchangers & Condensers
Superior thermal resistance + corrosion protection.
Applications:
Grades: S31803 • S32205 • S32750
🔹 4. Chemical & Petrochemical Plants
Chemical stability ensures long-life performance.
Used In:
🔹 5. Oil & Gas Processing
Handles aggressive, sour, high-pressure media.
Applications:
Grades: S32760 (excellent SCC resistance)
🔹 6. Marine, Shipbuilding & Firefighting Lines
Ideal for harsh, high-humidity marine environments.
Typical Uses:
| Application | Recommended Grade | Why |
|---|---|---|
| Off-shore & subsea | S32750 / S32760 | Highest chloride & pitting resistance |
| Desalination plants | S32750 | Very high PREN value for brine exposure |
| Chemical plants | S32205 | Balanced corrosion + mechanical strength |
| Heat exchangers | S31803 / S32205 | Stable thermal & corrosion resistance |
| Firewater lines | S32205 / S32760 | Stable in seawater + long service life |
| Type | OD Range | WT | Application |
|---|---|---|---|
| Duplex Tubes (A789) | 6–168 mm | 0.5–12 mm | Heat exchangers, chemical service |
| Super Duplex Tubes | 6–90 mm | 0.8–10 mm | Offshore, desalination |
| Pipe (A790) | ½”–20″ | SCH 10 to SCH 160 | Process piping |
(Custom sizes available on request.)
(Varies by grade, OD, WT & finish)
| Grade | Approx. Price (₹/kg) | Notes |
|---|---|---|
| S31803 / S32205 | ₹450 – ₹750 | Duplex grade stainless steel |
| S32750 / S32760 | ₹750 – ₹1,250 | Super Duplex grade stainless steel |
| Heat Exchanger Tubes | +10–20% premium | Additional testing and requirements |
Mandatory Tests (ASTM A789 / A790):
Special Tests (Critical for Duplex):
Documentation Provided:
Inox Steel India is a globally trusted supplier of Duplex 2205 (S31803/S32205) and Super Duplex 2507 (S32750/S32760) tubes that meet the demanding requirements of offshore, desalination, chemical, petrochemical, and marine applications. Our tubes undergo stringent quality control including ferrite testing, PMI, UT/EC, pitting resistance checks, and solution annealing, ensuring stable performance in chloride-rich and high-pressure environments.
✔ What Makes Our Duplex & Super Duplex Tubes Reliable
We ensure consistent, global-standard supply for critical industries.
| Industry | Application |
|---|---|
| Offshore & Subsea | Umbilicals, flowlines, manifolds |
| Desalination & RO | Brine circulation, HP piping |
| Chemical Processing | Acidic & chloride-rich media |
| Heat Exchanger OEMs | Tubes, condensers, heaters |
| Oil & Gas | Injection lines, offshore piping |
| Marine Engineering | Firewater lines, seawater systems |
| Power & Energy | Boiler & turbine auxiliary systems |
Our ASTM A789/A790 tubes provide superior durability in high-chloride, high-temperature & high-pressure conditions.
We supply Duplex & Super Duplex tubes to 50+ countries, ensuring maximum corrosion and impact protection during transit.
Packaging Includes:
Major Export Destinations:
UAE • Saudi Arabia • Oman • Qatar • Kuwait • Bahrain
Singapore • Malaysia • Vietnam • South Korea
Europe (UK, Germany, Italy, Netherlands)
USA • Canada • Mexico
South Africa • Kenya • Nigeria
We assist with:
✔ Grade selection — Duplex 2205 vs Super Duplex 2507
✔ Heat exchanger tubing design
✔ Offshore & desalination project requirements
✔ Material compatibility with chloride environments
✔ Bulk / OEM quantity-based pricing
52-A, Mulji Thackersi Bldg, Islampura Street, Shop No. 10, Near Alankar Cinema, Mumbai – 400 004
steel@inoxsteelindia.in
+91 9930796690
Offshore platforms, desalination plants, heat exchangers, petrochemical units, marine pipelines & chemical processing.
Yes — ferrite content (30–70%) is tested and certified as per ASTM.
Yes — Duplex and especially Super Duplex have excellent seawater corrosion resistance.
Yes — U-bent, straight, and cut-to-length tubes are available.
Inox Steel India supplies ASTM A789/A790 Duplex & Super Duplex tubes in grades S31803, S32205, S32750 and S32760. Ideal for offshore, desalination, chemical, petrochemical and heat exchanger applications. High-strength, chloride-resistant tubes with MTC 3.1.