Stage-by-stage material schedules
Map intake, high-pressure RO, permeate and concentrate as separate corrosion zones.
Industry solution · material selection
Stainless Steel for Desalination
Specify desalination stainless by process stage, chloride level, temperature, oxygen and oxidant exposure, pressure, velocity, crevice geometry and cleaning chemistry. The best stainless steel for desalination changes between intake, pretreatment, reverse osmosis, brine and thermal-evaporation equipment.
RO and thermal duties separated
Chloride, temperature and oxidant mapped
Crevices, welding and cleaning specified
Choose by component duty, not by industry label.
Use 2205 for many defined brackish or moderate seawater duties, 2507 or 6Mo grades for more aggressive high-chloride and oxidizing zones, and 316L only where exposure, temperature and crevice risk remain demonstrably moderate. Confirm every grade against the exact stream and component geometry.
Calling 316L seawater-proof
Permanent or hot seawater can pit and crevice-corrode conventional molybdenum austenitic grades.
Alloy margin versus fabrication control
Super duplex and 6Mo improve corrosion margin but demand qualified supply and welding.
Published data for the first material screen.
Desalination corrosion depends strongly on chloride, temperature, oxidants, oxygen, flow, shutdown and crevice design. The table is a screening map; project corrosion data and component qualification control final selection.
| Grade / designation | Structure | Desalination screening role | Primary benefit | Critical confirmation |
|---|---|---|---|---|
| 316L / 1.4404 / S31603 | Austenitic | Permeate, low-chloride and controlled utility zones | Availability and fabrication | Chloride, temperature, oxidant and crevices |
| 2205 / 1.4462 / S32205 | Duplex | Brackish water and selected seawater systems | Strength and chloride-SCC resistance | PREN, weld phase balance and exposure |
| 2507 / 1.4410 / S32750 | Super duplex | High-pressure seawater and brine systems | High localized-corrosion margin and strength | Welding, heat treatment and corrosion test |
| 254 SMO / 1.4547 / S31254 | 6Mo austenitic | Severe seawater components and heat exchangers | High pitting/crevice resistance | Availability, forming and matching consumables |
Conditions: Values are screening references at the stated product condition. Temperature capability, dimensional tolerances and acceptance properties must be fixed for the ordered product form. Start with the stainless steel grade directory, then request the applicable certificate and datasheet.
Specify the supply route with the grade.
Availability is confirmed at quotation. Every RFQ should identify product form, dimensions, condition, finish, edge, inspection evidence and downstream process.
| Product form | Starting grade | Condition / finish | Critical confirmation |
|---|---|---|---|
| High-pressure RO pipe | 2205 or 2507 by feed chemistry | Seamless/welded pressure pipe | Wall, pressure class, weld seam and corrosion test |
| Pump/valve component | 2507, 6Mo or qualified casting | Wrought/cast component route | Casting quality, crevices, seats and NDE |
| Thermal evaporator sheet/tube | Duplex, super duplex, 6Mo or titanium | Thin sheet and heat-exchanger tube | Temperature, brine concentration and joining |
| Permeate/utility piping | 316L or lean duplex where suitable | Clean pipe and fittings | Residual chloride, disinfection and finish |
A useful quotation is conditional, not generic. The desalination stainless supplier should confirm mill route, minimum order, certificate, tolerances and delivery condition against the finished component.
Compare options on the same service conditions.
Selection separates the primary advantage from the failure mode and fabrication burden. Review related industry solutions when the component crosses multiple service categories.
| Duty | Starting option | Advantage | Limitation | Alternative |
|---|---|---|---|---|
| Pretreated seawater line | 2205 | Strength and chloride-SCC resistance | Crevices and oxidants can exceed its margin | 2507 for more severe conditions |
| High-pressure RO concentrate | 2507 | High localized-corrosion resistance | Fabrication and availability require control | 6Mo for selected component geometry |
| Permeate system | 316L | Available and readily fabricated | Residual disinfectant/chloride must stay controlled | 2205 if chemistry or load is more severe |
| Hot brine evaporator | 6Mo/super duplex after review | High chloride margin | Temperature and concentration can remain extreme | Titanium or nickel alloy by process study |
Application duties, limits and maintenance.
Each card uses the same five-point structure so service, grade, reason, limitation and maintenance can be checked without leaving gaps.
Reverse-osmosis high-pressure train
ServiceFiltered seawater, high pressure, oxygen, oxidant residual and concentrate.
Starting grade2507 for severe high-pressure wetted parts; 2205 where corrosion review supports it.
Why it worksDuplex families combine high strength with chloride-SCC resistance.
LimitsFlanges, gasket faces, dead legs and poor weld heat treatment remain vulnerable.
MaintenanceTrack feed chemistry, oxidant, pressure, leaks, deposits and weld condition.
Thermal desalination evaporator
ServiceHeated and concentrated brine, heat transfer, scale and shutdown exposure.
Starting grade6Mo, super duplex or another process-qualified alloy by temperature and concentration.
Why it worksHighly alloyed stainless provides improved localized-corrosion margin.
LimitsScaling creates under-deposit chemistry and reduces heat transfer.
MaintenanceControl antiscalant, cleaning chemistry, tube condition and stagnant shutdowns.
Permeate and product-water system
ServiceLow-salinity product water, disinfection, storage and distribution.
Starting grade316L or a qualified lean-duplex route for defined product-water chemistry.
Why it worksSmooth stainless surfaces support hygienic and low-maintenance distribution.
LimitsResidual chlorides, disinfectant concentration and poor draining can still attack crevices.
MaintenanceMonitor disinfectant, rinse after cleaning and inspect weld tint and dead legs.
Failure modes to control
PittingChloride and oxidant exceed passive-film stabilityControl: Raise alloy margin and control chemistry/temperature.
Crevice corrosionStagnant seawater concentrates beneath gaskets or depositsControl: Design out tight crevices and select a resistant grade.
Weld-related attackWrong heat input or filler leaves poor duplex phase balanceControl: Qualify welding and verify ferrite/corrosion performance.
Under-deposit corrosionScale or biofouling creates concentrated local chemistryControl: Control pretreatment, cleaning and inspection.
Standards belong in the purchase specification.
Designations from ASTM, EN, UNS, ISO or a manufacturer range are not automatically interchangeable. Match chemistry, properties, product form, condition and test requirements.
| Standard / reference | Role | Procurement caveat |
|---|---|---|
| ASTM A240 / EN 10088 | Stainless plate and sheet requirements | Specify exact grade, condition, dimensions, finish and tests. |
| ASTM A789 / A790 | Duplex tube and pipe requirements | Use the product standard matching tube or pipe and ordered heat treatment. |
| ASME B31.3 | Process piping for desalination systems where adopted | Coordinate materials, fabrication, examination and pressure testing. |
| ASTM G48 | Laboratory pitting/crevice corrosion test methods | Fix method, temperature, acceptance and sampling in the purchase order. |
Source note: Always use the current edition adopted by the project. Standards establish material or design requirements; they do not replace application engineering or finished-product validation.
Stainless Steel for Desalination questions.
What is the best stainless steel for desalination?
2205, 2507 and 6Mo grades are common screening families, but process stage, chloride, temperature, oxidant, pressure and crevices decide.
Can 316L handle seawater?
It can suit limited moderate or intermittent duties, but it should not be assumed suitable for permanent, hot or stagnant seawater.
Why is super duplex used in RO plants?
Its high strength and localized-corrosion resistance support high-pressure, chloride-bearing systems when welding and heat treatment are controlled.
What changes in thermal desalination?
Heating and concentration raise corrosion and scaling severity, so brine chemistry and heat-transfer geometry become central.
Why specify ASTM G48 testing?
It can verify a defined localized-corrosion acceptance for duplex or high-alloy products and welds when the test conditions are stated.
What should a desalination stainless supplier quote?
Include process stage, full water analysis, temperature, pressure, oxidants, grade, form, dimensions, welding, corrosion test and delivery.
Worked specification route for a seawater reverse-osmosis header.
This illustrative engineering workflow shows how a service requirement becomes a material and supply specification. Final recommendations depend on the confirmed design, manufacturing route, inspection plan and finished-product validation.
Define the component duty
A high-pressure header must carry pretreated seawater and concentrate without localized-corrosion failure.
Fix the operating limits
Chlorides, temperature, oxidant residual, pressure, velocity, gasket geometry and cleaning are fixed.
Compare viable material routes
Compare 2205, 2507 and 6Mo using the most severe operating and shutdown conditions.
Write the purchase specification
Order pipe, fittings and flanges with controlled heat treatment, welding, G48 acceptance and PMI.
Verify the acceptance plan
Release after certificates, PMI, weld/NDE review, corrosion tests, pressure test and crevice inspection.
Project validation package: record the approved design, dimensions, process route, inspection method, delivery evidence, verified outcome, limitations and technical sign-off before material approval.
Material references and selection support.
The manufacturer and standards references below support the material information on this page. Suitability depends on the ordered product form, condition and service environment; send your requirements for a source-backed quotation response.
World Stainless, Desalination in Stainless Steel
Official application guidance on aggressive seawater/brine service and stainless use.
Outokumpu, Desalination case study
Process-stage, salt, oxygen and temperature context for duplex selection.
Outokumpu Duplex Grades
2205 and super-duplex properties and desalination application context.
Outokumpu High-performance Austenitic Grades
6Mo and high-alloy stainless application context for severe seawater duties.
Need help checking your operating conditions?
Send the grade, product form, dimensions and service conditions through the quote request.
What to include
Include the applicable standard, quantity and delivery target. We can clarify documentation available for the ordered product.
Related grade-specific pages
Send a desalination systems material brief for engineering review.
Use the site quotation modal and include what is known. Unknown items can be marked for review so grade, product form, processing, evidence and supply route are considered together.
Desalination process and component
Complete feed/brine water analysis
Temperature, pressure and velocity
Oxidant, oxygen and cleaning chemistry
Grade, PREN and product standard
Pipe, tube, plate or fitting dimensions
Welding, PMI, NDE and corrosion tests
Quantity, destination and due date