EN 10253-2 Type B buttweld pipe fittings for seawater reverse osmosis (SWRO), multi-stage flash (MSF), and multi-effect distillation (MED) desalination plants. Warm Gulf seawater and brine concentrate are among the most aggressive natural chloride environments — material selection must account for temperature, chloride concentration, and crevice geometry, not just PRE number alone.
| System Area | Grade | W.Nr. | PRE | Note |
|---|---|---|---|---|
| Seawater intake (ambient, <25°C) | Duplex 2205 | 1.4462 | ≥35 | Minimum at cool seawater |
| Seawater intake (Gulf / warm, 25–35°C) | Super Duplex 2507 | 1.4410 | ≥40 | Duplex marginal at Gulf temperatures |
| Hypochlorite dosing lines (pre-treatment) | 254 SMO / Inconel 625 | 1.4547 / 2.4856 | ≥43–51 | Hypochlorite highly aggressive at temperature |
| HP seawater feed to SWRO membranes | Super Duplex 2507 | 1.4410 | ≥40 | High pressure + high chloride |
| Brine concentrate discharge | Super Duplex 2507 / 254 SMO | 1.4410 / 1.4547 | ≥40–43 | Brine = ~2× seawater chloride concentration |
| MSF brine heater tubes / header | 254 SMO | 1.4547 | ≥43 | Hot concentrated brine above 250°C limit for duplex |
| Chemical dosing (antiscalant, acid) | 316L | 1.4404 | ~24 | Closed dosing system, low chloride |
| Product water (permeate) distribution | 316L | 1.4404 | ~24 | Very low chloride treated water |
The workhorse for warm Gulf seawater: intake, HP feed, firewater. 250°C temperature ceiling — not suitable for MSF brine heater service. NACE MR0175 qualified.
Full grade page →Hot brine, MSF brine heaters, hypochlorite service above 30°C, and locations where temperature exceeds the duplex 250°C ceiling. Fully austenitic — no intermetallic restriction.
Full grade page →Highest-risk seawater locations: pump suction headers at high temperature, concentrated hypochlorite dosing, crevice-critical connections where PRE ≥43 is still marginal.
Full grade page →Product water (permeate), chemical dosing closed systems, clean utility, instrument air. Not suitable for direct seawater or brine contact.
Full grade page →A PRE number alone does not predict pitting performance. Crevice geometry, stagnant conditions, biofilm, and temperature all interact. Gulf seawater at 35°C with even modest crevices at gasketed joints demands PRE ≥40 minimum (Super Duplex 2507). At 40°C with crevice risk, 254 SMO (PRE ≥43) or Inconel 625 (PRE ~51) is required. Duplex 2205 (PRE ≥35) is appropriate for cold-seawater intakes only — never specify it for warm Gulf open-seawater service without corrosion engineering review.
EN 10204 3.1 standard. EN 10204 3.2 (TÜV / Bureau Veritas) on request. NACE MR0175 documentation for sour service areas. PED 2014/68/EU. Exporting to Saudi Arabia, UAE, Oman, Qatar, and Kuwait — shipping documentation for Gulf projects available.
