Super duplex & nickel valve alloys

Last updated 12 August 2026

Valves are one of the most demanding applications we supply. A body, stem or trim component has to hold pressure, resist corrosion and erosion, and remain serviceable for the design life of the installation, often in conditions where standard austenitic stainless steels will not survive.

We have supplied duplex, super duplex, nickel and copper alloys to valve manufacturers for decades, as bar and plate, from stock in the UK and USA.

Which alloy is best for seawater and subsea valve components?

Ferralium^® 255-SD50 (UNS S32550) is the reference material for subsea valve stems, choke internals and pressure retaining parts, combining a minimum 0.2 percent proof stress of 586 N/mm2 (annealed bar up to 12 inches) with resistance to chloride pitting and crevice corrosion. It is particularly suited to larger sections, where sigma phase formation is less likely than with other super duplex grades.

Alloy 32760 (F55) and Alloy 32750 (F53) are widely specified for bodies, bonnets and stems, both offering a PREN above 40.

Which alloy for sour service and upstream oil and gas valves?

Alloy 2205 covers general pressure containing parts, moving to super duplex as chloride levels or strength demands increase. For high strength trim, stems and springs in sour conditions, Alloy 718 and Alloy 725 are the standard choices, with Alloy 925 where cost and strength need balancing.

All can be supplied to NACE MR0175 and ISO 15156 subject to the hardness limits the standard sets, so send us the specification with the enquiry.

Which alloy for acid and chemical processing valves?

Alloy 825 and Alloy 625 handle aggressive acid service, including sulphuric and phosphoric duty and chloride bearing process streams. Alloy 2205 and the super duplex grades cover a large part of the middle ground at significantly lower cost.

Which alloy for valve stems where galling is the problem?

Galling is a different failure mode from corrosion and needs a different answer. Fermonic^® 60 (Nitronic^® 60) is specified precisely because it runs against stainless steel without seizing, making it the choice for stems, glands and seat rings in metal-to-metal contact.

Fermonic^® 50 gives strength with better corrosion resistance than standard austenitics. Hiduron^® 130 covers valve spindles and actuator stem nuts where seawater performance, galling resistance and low magnetic permeability are needed together.

What size bar can you supply for one-piece valve bodies?

Send us the size and we will confirm from current stock. Solid bar and plate are held across the range for one-piece bodies, closures and end connections, which shortens lead time against forgings.

Also known as

Ferralium^® 255 is the Langley Alloys trade name for the super duplex stainless steel UNS S32550. Alloy 32760 is equivalent to UNS S32760, also known as Zeron 100^®, a trademark of Rolled Alloys. Alloy 32750 is equivalent to UNS S32750, also known as SAF 2507^®, a trademark of Alleima. Fermonic^® 50 and Fermonic^® 60 are our designations for UNS S20910 and UNS S21800, known elsewhere as Nitronic 50 and Nitronic 60, trademarks of Cleveland-Cliffs (formerly AK Steel). Alloy 625, Alloy 718 and Alloy 725 are equivalent to UNS N06625, N07718 and N07725, sold elsewhere as Inconel^® 625, Inconel 718 and Inconel 725, trademarks of Special Metals. If your drawing calls out a trade name we have not listed, send it to us and we will confirm the matching grade.

Typical valve components

Bodies and bonnets, closures, stems and spindles, balls, gates and wedges, discs, seats and seat rings, glands and gland followers, actuator stem nuts, body bolting, bushings and bearings.

Why valve manufacturers buy from us

Stock across the full grade range, so you can quote and deliver without waiting on a mill run.
Sawing and cut-to-length to reduce machining time.
Technical support on grade selection and international equivalence, including competitor trade names.

We supply bar and plate to valve manufacturers and their machining subcontractors, cut to length where that saves you machining time.

Related sectors: oil and gas, marine and offshore, and chemical processing. Related applications: pumps and fasteners. See also our material calculators for PREN and equivalents lookups.

EN 10204 3.1 certification comes as standard on all material, with 3.2 third party inspection and NACE MR0175 / ISO 15156 compliance available where specified.

Our own machining plant takes material further where it helps, through first and second-stage machining to proof-machined and finished-machined components, at our own Midlands plant.

Member of the British Valve & Actuator Association

Grade comparison

Grade	UNS / designation	PREN	Min 0.2% proof
17-4 PH	UNS S17400, EN 1.4542, AMS 5643	n/a	380 N/mm²
Alloy 2205	UNS S32205, UNS S31803, EN 1.4462	36*	450 N/mm²
Alloy 625	UNS N06625, W.Nr. 2.4856, AMS 5666	n/a	415 N/mm²
Alloy 718	UNS N07718, W.Nr. 2.4668, ASTM B637	n/a	827 N/mm²
Alloy 725	UNS N07725, NACE MR0175 / ISO 15156, ASTM B805	n/a	827 N/mm²
Alloy 825	UNS N08825, W.Nr. 2.4858, NACE MR0175 / ISO 15156	n/a	241 N/mm²
Fermonic^® 50	UNS S20910, ASTM XM-19, 1.3964	34*	380 N/mm²
Fermonic^® 60	UNS S21800, ASTM A276, ASTM A479	21*	379 N/mm²
Hiduron^® 130	Hidurax Special, DIN 2.1504, DTD 900/4805	n/a	630 N/mm²
Ferralium^® 255	UNS S32550, UNS S32520, 1.4507	40*	586 N/mm²
Alloy 32750	UNS S32750, 1.4410, NACE MR0175 / ISO 15156	43*	550 N/mm²
Alloy 32760	UNS S32760, 1.4501, NACE MR0175 / ISO 15156	42*	550 N/mm²

* PREN calculated from each grade's composition (Cr + 3.3x(Mo + 0.5W) + 16xN), and shown as n/a for alloys where PREN does not apply, such as the nickel and copper grades. Every other figure is pulled from the grade's own datasheet-sourced ACF fields; where no sourced value exists, the cell links to the datasheet.

Common questions

What is the difference between F53, F55 and Ferralium^® 255?

All three are super duplex stainless steels with a PREN above 40. F53 is UNS S32750 and F55 is UNS S32760, both 25 percent chromium grades. Ferralium^® 255 is UNS S32550, which carries a higher minimum proof stress and is less prone to sigma phase formation in large sections.

Can you supply material equivalent to Zeron 100?

Yes. Zeron 100 is UNS S32760, which we stock as Alloy 32760. Provided your specification calls out the UNS number rather than the proprietary name alone, the material is directly equivalent and we can supply the documentation to demonstrate it.

Do you supply material to NACE MR0175 and ISO 15156?

Yes, where the grade and delivery condition allow it. The hardness limits set out in the standard usually determine the delivery condition, so tell us the specification when you enquire. We supply the certification alongside the EN 10204 3.1 material certificate.

Which alloy should I use for valve stems?

For seawater and chloride service, super duplex or Ferralium^® 255. For sour service at high strength, Alloy 718 or 725. Where galling against the gland is the recurring failure, Fermonic^® 60.

What is the largest bar diameter you stock?

It varies by grade and changes with stock levels, so send us the size and we will confirm from current stock rather than publish a figure that could be wrong on the day you enquire.

Do you supply finished valve components?

Yes and no. We supply the material as bar, plate and pipe to valve manufacturers and their machining subcontractors, cut to length to save machining time.

Is Alloy 316L suitable for valve components in seawater?

Generally not for long term immersion. Alloy 316L has a PREN of around 25, which suits rural, urban and estuary environments but is limited in exposed coastal settings. Duplex 2205 at a PREN of around 34 handles estuary and offshore duty, and sustained immersion usually calls for a super duplex grade.

How quickly can you supply?

Most of the range is available from stock from the UK or USA. We do not publish a stock list because it changes daily, so contact the sales team with the grade and size for current availability.