Product Specification

ASTM A790 UNS S32750 / 2507 Duplex Stainless Steel Pipe for Water Desalination

ASTM A790 2507 duplex stainless steel pipe is a super duplex pipe product specified for seamless and straight-seam welded ferritic/austenitic stainless steel pipe used in corrosive service, especially where chloride-induced pitting, crevice corrosion, and stress corrosion cracking are design concerns. For seawater desalination, UNS S32750 is one of the most proven material choices for high-pressure piping, reverse osmosis skids, seawater transfer lines, and heat-exchanger service because it combines a high PREN level, minimum 0.2% proof strength of 550 MPa, and strong resistance in aggressive chloride-bearing media.

Specifications

Main Features

1. High localized corrosion resistance in chloride media
   SAF 2507 has a nominal chemistry of about 25% Cr, 4% Mo, and 0.3% N, and Alleima reports a minimum PRE value of 42.5 for seamless tubes, placing it firmly in the super duplex class for severe seawater duty.
2. High strength for pressure-bearing desalination lines
   In the solution-annealed condition, tube and pipe up to 20 mm wall thickness have minimum yield strength 550 MPa, minimum 1.0% proof strength 640 MPa, tensile strength 800-1000 MPa, and minimum elongation 25%.
3. Strong resistance to chloride stress corrosion cracking
   ASTM A790 itself emphasizes corrosive service with particular attention to SCC, while duplex/super duplex grades are widely selected where austenitic grades are vulnerable in chloride-rich systems.
4. Suitable for seawater reverse osmosis systems
   ISSF’s desalination guidance notes that super duplex stainless steel is used in high-pressure piping on the seawater reverse osmosis side because it resists the severe corrosivity of seawater together with the required operating pressure. Alleima also lists desalination plants, pressure vessels for RO units, seawater transport pipe, and heat exchanger tubing among typical SAF 2507 applications.
5. Good fabrication and weldability when properly controlled
   IMOA’s fabrication guidance notes duplex grades require controlled fabrication practice, especially heat input and post-fabrication metallurgical balance, which is critical for maintaining corrosion performance in desalination assemblies.

Our Advantages

1) Concern: “Will the pipe resist pitting and crevice corrosion in warm seawater and brine?”

Yes. The key engineering basis is the super duplex chemistry itself. SAF 2507 has a minimum PRE value of 42.5 for seamless tubes, and duplex guidance from the Nickel Institute identifies super duplex grades with PRE around 40 or higher as commonly selected for seawater-exposed and other severe chloride applications.

2) Concern: “Will it handle RO system pressure without forcing excessive wall thickness?”

Yes. UNS S32750 offers minimum 550 MPa yield strength and 800-1000 MPa tensile strength in tube/pipe form, which gives designers much more mechanical margin than standard austenitic stainless steels and often supports lighter, more compact pressure piping designs.

3) Concern: “Is 2507 actually used in desalination service, or only described that way in theory?”

It is used in real desalination duty. ISSF states super duplex stainless is used in SWRO high-pressure piping, and Alleima explicitly lists reverse osmosis pressure vessels, seawater transport tube/pipe, and desalination plant service for SAF 2507.

Execution Standards

Application Field

Seawater reverse osmosis high-pressure piping spool
A typical single-product application is the high-pressure piping spool between the RO high-pressure pump discharge and the membrane pressure-vessel header, where the pipe must withstand chloride-rich seawater, elevated pressure, and long-term corrosion-fatigue risk. ISSF and Alleima both identify this type of SWRO duty as a core use case for super duplex stainless steel.

Chemical Composition

The table below gives representative chemistry for five commonly referenced duplex and super duplex grades used for comparison in procurement and engineering selection. Values are nominal or standard-grade ranges from the cited grade datasheets.

Mechanical Properties

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A: Generally speaking,it is 10-15 days if the goods are in stock,or it is 30-40 days if the goods are not in stock,

it is according to quantity.

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A: Yes, we could offer the sample for free charge but need pay the cost of freight.

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A: Payment<=2000USD, 100% in advance. Payment>=2000USD, 30% T/T in advance ,balance before shippment.

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