Two grades are often specified in duplex stainless steel engineering specifications for pressure vessels or piping systems, chemical processing equipment and seawater systems: 2205, the workhorse, and 2507, a super-duplex, with a higher alloy content. The choice between the two comes down to balancing rust resistance with mechanical strength, cost and weldability — as well as ensuring that the grade is suitable for your service environment.
In this guide we at Jay Steel Corporation, a leading super duplex sheets exporter in India help you understand all you need to know about UNS S32750 and UNS S32760 grades so that you can choose the right material for your project.
What are these grades?
- 2205 Duplex — also known as UNS S32205 and S31803. This is the most commonly used duplex, with roughly twice the strength as 300-series austenitic. It also offers significantly better resistance to stress corrosion cracking and chloride pitting compared with 304/316. Rolled Alloys
- 2507 – (Super Duplex, UNS 32750) — Higher Cr, Mo, and N levels than 2205, providing markedly improved resistance to localized corrosive corrosion, and higher strength. Often specified when severe chloride exposure, or high pressure/temperature, are involved. Sandmeyer Steel Company+1
- UNS-S32760 — an enhanced super-duplex that is sometimes used for extreme conditions. It contains additional alloying components (e.g. W, Cu) which increase the resistance to pitting. Smith Metal+1
The key metric for assessing resistance is the pitting resistance:
The Pitting Resistance Equivalent number (PREN), is a quick and easy way to compare the resistance to pitting in chloride environments: the higher PREN, then the better performance you can expect to achieve. In industry literature, typical PREN values are:
- 2205: PREN35 — suitable for chloride-containing areas, splash zones, and desalination feed component. Steel Pipes Factory
- 2507: PREN40-42 – Significantly better corrosion resistance in localized areas; used for seawater and offshore umbilical, as well as aggressive chemical applications. Fushun Special Steel+1
- S32760 PREN is higher than 2507 depending upon the exact chemical composition — used when operators require maximum safety against pitting. Neon Nickel+1
If you are using warm chloride solutions or produced water in your process, or if you anticipate long-term service near seawater, S32760 (or 2507 for the most severe exposures) will reduce the risk of crevice and pinhole formation compared to 2205.
- Strength and mechanical performance:
The Duplex microstructure provides higher yield strength than austenitics. The yield of 2205 is roughly double that of 316L. 2507 increases the allowable stress, allowing lighter and thinner sections to be used for the same load. This is a great benefit for applications where weight-sensitive materials are required (e.g. subsea hardware or risers). Super duplex (2507) can be a cost-effective choice for designs that require higher pressure ratings but do not need to increase wall thickness. Rolled Alloys+1
- Fabrication and welding:
Welders have a good understanding of the behavior and welding consumables, (ER2209 and E2209), and are familiar with post-welding practices. Weldability of 2507 is good, but it’s more sensitive. Controlling heat input, the interpass temperature and matching your filler metals to prevent phase balance shifts are key. Discuss procedures with your material supplier for thin gauge sheet work or complex fabrications. Jay Steel Corporation provides certified plate and guidance). Rolled Alloys+1
- Cost and availability
The 2205 alloy is less expensive than the 2507 and has a wider range of stock. The higher Ni/Mo/W contents and stricter production control of super-duplex (UNS 32750 and UNS S32760 in particular) alloys command a premium price. When life-cycle costs and maintenance risks are taken into account, however, the premium price for 2507 may be justified, especially in environments with high levels of aggression where failure or downtime is costly. Jay Steel Corporation is a super-duplex sheets exporter to India and can provide competitive quotes for material forms such as 2205, 2507, and S32760 (sheets. plates. pipes. flanges).
What grade is appropriate for what project?
- Select 2205 for: moderate chlorine exposure, chemical service in general, and when availability/cost are the primary concern (e.g. process tanks, exchangers under brackish conditions, most onshore chemical plants). Rolled Alloys
- Use 2507 (UNS 32750) for: high chloride brines in subsea or offshore hardware applications, thin-wall designs, or when you require higher strength and temperature at elevated temperatures. Sand Meyer Steel Company+1
- UNS S32760 is the right choice when: you are working in an environment that is extremely aggressive (highly acidic chlorine streams, heavy salt brines or long-term immersion in seawater) and want to get the best corrosion resistance possible. Quest4Alloys+1
Specification tips
- It is better to specify PREN requirements (e.g. “PREN >=40”) than just a company name. This will make supplier comparisons more objective. Wikipedia
- In the procurement documents, specify welding filler (if needed) and PWHT. Rolled Alloys
- Ask for mill certifications, heat trace on critical alloys, and traceability when ordering super duplex sheets. Their higher alloying demands stringent quality assurance. Sand Meyer Steel Company
There is no “better” grade, only the grade that’s right for you. 2205 offers a proven and cost-effective solution for chloride-containing applications. 2507, (UNS 32750) provides enhanced corrosion and strength for offshore, seawater and highly corrosive processes. UNS 32760 meets the highest demands. Super duplex (2507, S32760) will maximize service life and minimize pitting in chloride-rich environments. If you are sourcing materials, make sure to work with a supplier who has experience.
Contact Jay Steel Corporation for reliable supplies and expert advice when selecting UNS 32750, UNS 32660, or 2205 in sheet, pipe, or plate form. They are also a trusted super duplex sheets exporter in India. They can match the grade, finish and certificate to your project requirements and provide competitive quotes.
