On this page 12 sections
Which stainless steel is used in desalination plants?
Short answer
Reverse-osmosis plants usually run product water and low-chloride chemical lines in SS 316L, low-pressure seawater and pre-treatment in duplex 2205 or 6Mo, and high-pressure RO piping in super duplex 2507, which combines PREN above 40 with high strength. Thermal plants rely more on titanium and cupro-nickel tubes.
Key takeaways
In brief
- Product water and low-chloride lines: SS 316L is often adequate for permeate and product water and for chemical dosing lines with low chlorides.
- Pre-treatment and low-pressure seawater: Duplex 2205 or 6Mo are used depending on temperature and chlorination.
- High-pressure RO: Super duplex 2507 dominates RO high-pressure piping because of its strength and PREN above 40.
- Thermal plants: Titanium and cupro-nickel tubes remain standard for brine heaters and condensers.
Product water and low-chloride lines
SS 316L is often adequate for permeate and product water and for chemical dosing lines with low chlorides.
Pre-treatment and low-pressure seawater
Duplex 2205 or 6Mo are used depending on temperature and chlorination.
High-pressure RO
Super duplex 2507 dominates RO high-pressure piping because of its strength and PREN above 40.
Thermal plants
Titanium and cupro-nickel tubes remain standard for brine heaters and condensers.
Why super duplex took over high-pressure RO
High-pressure RO lines carry seawater at roughly 60–80 bar. 2507 has about twice the yield strength of SS 316L, so walls can be thinner for the same rating, which cuts weight, welding time and cost. Its PREN above 40 also gives margin against crevice corrosion at Victaulic-type couplings and flange faces, where earlier SS 316L and SS 904L installations suffered.
Brine and concentrate lines
Brine reject from RO is roughly twice as salty as the feed seawater. Super duplex or 6Mo is normally used where brine stays wet in metal piping, and non-metallic piping is common for low-pressure discharge lines.
Ordering points for desalination projects
Related guides, comparisons and articles
Frequently asked questions
Is SS 904L suitable for RO high-pressure piping?
SS 904L has a PREN of about 34–36, below the level usually required for high-pressure seawater, and lower strength than super duplex. Most new plants use super duplex 2507.
Why not use duplex 2205 for seawater?
With a PREN of about 35, 2205 is good for brackish water and pre-treatment, but it is marginal for warm seawater with crevices. Super duplex is the safer choice for immersed seawater service.
Do you supply desalination projects in the GCC?
Yes. We supply duplex, super duplex, 6Mo and titanium products to desalination projects in the UAE, Saudi Arabia, Oman and Qatar, with EN 10204 3.1 or 3.2 certificates.
Does Bright Tubes supply the materials discussed in this article?
Yes. Super Duplex 2507 Stainless Steel, Duplex 2205 Stainless Steel and related products are supplied from stock or mill-sourced, with EN 10204 certificates.
Can I get technical advice for my application?
Yes. Share your service conditions and specification, and our team can help shortlist suitable grades for your engineer to confirm.