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When a pipeline lives in chlorinated seawater, sour gas, or a scrubber stack, ordinary stainless steels fail on a clock - 316L can pit in 2–5 years. Super Duplex 2507 is the grade engineered to outlast the asset, not just the warranty. It is a 25 % chromium – 4 % molybdenum – 7 % nickel ferritic-austenitic (duplex) stainless steel whose two-phase structure delivers 6Mo-class corrosion resistance at a fraction of the titanium cost, with roughly twice the strength of 316L.

≥ 42

PREN (pitting resistance)

550 MPa

Min. yield strength

800 MPa

Min. tensile strength

< 600°F

Max. service temperature

Element Of Super Duplex 2507 Pipe

2507 is not a single magic element - it is a balanced recipe where each addition earns its place. Read the chemistry as a job description:

Chromium (24–26 %): builds the passive film that shrugs off oxidizing and chloride attack.

Molybdenum (3–5 %): the pitting/crevice killer - the more Mo, the higher the PREN.

Nitrogen (0.24–0.32 %): strengthens the austenite, boosts PREN, and locks the phase balance.

Nickel (6–8 %): supplies ductility and toughness to the austenitic half of the duplex.

Low Carbon (≤0.030 %): starves carbide precipitation, so intergranular corrosion stays away.

Iron (balance) + capped Mn/Si/P/S/Cu: the ferritic backbone plus tight impurity limits.

That balance is why 2507 hits PREN ≥ 42 - the widely accepted threshold (PREN > 40) for resisting seawater pitting - while staying weldable and fabricable.

Element	C	Mn	P	S	Si	Cr	Ni	Mo	N	Cu	Fe
S32750 (2507)	≤0.030	≤1.20	≤0.035	≤0.020	≤0.80	24.0–26.0	6.0–8.0	3.0–5.0	0.24–0.32	≤0.50	Bal.

Excellent Corrosion Resistance Of Super Duplex 2507 Pipe

Corrosion Threat	What 2507 Does About It
Chloride pitting	PREN ≥ 42 keeps the critical pitting temperature at 50–60°C - far above 316L's ~15–20°C.
Crevice corrosion	High Cr/Mo/N resist attack at flange faces, gaskets and under-deposit zones.
Chloride stress corrosion cracking	The ferritic phase is inherently resistant in warm, chloride-bearing service.
Intergranular corrosion	Low carbon minimizes carbide precipitation during heat treatment and welding.
Organic & inorganic acids	Strong against formic/acetic acids and chloride-bearing inorganic acids; resists dilute HCl.
Uniform corrosion	Suitable for ~19,000 ppm seawater chloride without protective coatings.

Strength Of Super Duplex 2507 Pipe

Property	Value (UNS S32750, annealed)
Tensile Strength, min	800 MPa (116 ksi)
Yield Strength, min	550 MPa (80 ksi) - ≈ 3.2× 316L
Elongation, min (2 in.)	15 %
Hardness, max	32 HRC (≈ 310 HBW)
Modulus of Elasticity	27.5 × 10⁶ psi (≈ 190 GPa)
Mean Coeff. Thermal Expansion	7.2 × 10⁻⁶ in/in/°F (low - good dimensional stability)
Thermal Conductivity	98 BTU·in/ft²·h·°F
Density	7.80 g/cm³ (7800 kg/m³)
Max Service Temperature	600°F / 316°C (avoid long exposure above this)

Where 2507 Goes to Work

Offshore & Subsea

Platform topside & seawater piping - cooling, firewater, injection lines (bare, uncoated).

Subsea umbilicals and flowlines, risers and manifolds.

Heat-exchanger and condenser tubes in chloride-laden service.

Desalination & Water

SWRO high-pressure piping and seawater intake/distribution systems.

Chemical, Petrochemical & Energy

Process pressure vessels, piping and reactors; FGD / flue-gas scrubbing equipment.

Pulp & paper digesters and bleach plants.

Spec It Your Way

Product Form	Typical Size Range	Wall / Schedule	Length
Seamless Pipe (A790)	1/2"–24" (≈21–610 mm OD)	SCH 5S–XXS	1–16 m / random
Welded / EFW Pipe (A928, A790)	up to 48"–100" large dia.	SCH 5S–XXS	up to 12 m
Tube (A789)	1/16"–4" OD (≈1.6–102 mm)	0.010"–0.220" wall	cut or coils to ~24,000 m
Subsea Umbilical (A789)	3/8"–1-1/2" OD	0.039"–0.125" wall	coils to 80,000 ft
Fittings (A815) / Flanges (A182 F53)	1/2"–24"	150# / 300#	-

r Duplex 2507 Pipe

Standards & Finishes

Pipe: ASTM A790 (Smls/Welded) · Welded: ASTM A928 Cl.5 · Tube: ASTM A789 · Plate: A240 · Bar: A276 · Flanges: A182 F53 · Fittings: A815.

Dimensions to ASME B36.10 / B36.19; metric sizes available.

Ends: Plain (PE), Beveled (BE), Threaded. Finish: solution-annealed & pickled, bright-annealed, or polished.

Heat treatment: solution annealed and water-quenched (≈1020–1100°C) to lock the ~50/50 phase balance.

Questions Engineers Actually Ask

Can 2507 replace 316L or 2205 directly?

Mechanically yes with re-rated (thinner) walls; corrosion-wise it is a strict upgrade. Re-check the design code and welding procedure - 2507 needs duplex-qualified filler (e.g., ER2594 / E2594) and controlled heat input.

Does it need coating or cathodic protection?

No. Bare 2507 delivers 25+ year life in seawater without coating or CP - a major lifecycle-cost advantage, though crevice designs (flange faces) should still respect the critical crevice temperature.

Is it weldable in the field?

Yes. GTAW/TIG, GMAW/MIG and SAW are all used; no preheat is normally required, with post-weld heat treatment generally unnecessary. Control interpass temperature to preserve the phase balance.

What about NACE / sour service?

Pure seawater does not require NACE MR0175; if injection lines may see produced water / H₂S, qualify per NACE MR0175 / ISO 15156.