Desalination
Nickel Alloys for Hot Seawater, Brine and Evaporator Duty
Industry Overview
Cold seawater is a materials problem most alloys can solve. Hot, deaerated, concentrated brine is not. Above roughly 60°C and at 70,000 ppm TDS and higher, the crevice-corrosion and chloride-SCC margins of duplex and super duplex narrow quickly, and thermal MED/MSF evaporators introduce condensing vapour plus CO₂ and H₂S. TOKO ALLOY supplies Monel 400, Inconel 625 and Incoloy 825 for the parts of a desalination plant that sit in that window — evaporator tubing, brine heaters, vapour-side components and high-pressure membrane feed where duplex is marginal.
Key Challenges
Hot Concentrated Brine
Brine discharge runs at 70,000+ ppm TDS and the absence of oxygen removes the protective oxide that would otherwise regenerate. This is the condition where duplex grades lose their margin and a nickel alloy becomes the engineering answer rather than a premium option.
Thermal MED / MSF Evaporator Tubing
Evaporator bundles see hot brine on one side and condensing vapour on the other, with CO₂ and non-condensable gases in the vapour. Monel 400 has been the reference material here for over a century; Inconel 625 and Incoloy 825 cover the higher-temperature and higher-chloride ends.
High-Pressure SWRO Feed at 55–82 bar
Membrane feed trains need high strength and chloride resistance together. Where the water is aggressive enough that duplex 2507 is at its limit, Inconel 625 pipe provides PREN > 45 at 414 MPa minimum yield.
Chlorination and Antiscalant Dosing
Chlorine, hypochlorite and acid dosing lines are small bore but the most aggressively attacked in the plant — oxidising chloride at high concentration. Hastelloy C-276 and C-22 are the alloys that survive wet chlorine without pitting.
TOKO ALLOY Solutions
Monel 400 Evaporator Tubing (N04400)
ASTM B163 tube and B165 pipe. The classic MED/MSF evaporator material: 67% Ni / 23% Cu, strong from cryogenic to 480°C, and resistant to seawater and brine at the velocities evaporator bundles actually run.
Inconel 625 for High-Chloride Brine Service (N06625)
ASTM B444 pipe and B704/B705 tube with PREN > 45 for brine heaters, high-pressure feed and vapour-side components where duplex 2507 does not leave enough margin. Niobium-stabilised, so the heat-affected zone keeps its corrosion resistance after welding.
Incoloy 825 for Acid-Dosed and Sour Brine (N08825)
ASTM B423 pipe for lines carrying acidified or H₂S-bearing brine, where the copper addition resists both the sulfuric acid from dosing and the reducing conditions from deaeration.
C-276 / C-22 for Chlorination and Dosing Lines
ASTM B622/B619 small-bore pipe and B626 tube for hypochlorite generation, chlorine dosing and antiscalant injection — the oxidising, high-chloride duty where standard grades pit through at the weld.
Recommended Materials Desalination
View detailed chemical composition, mechanical properties, and corrosion resistance data for each recommended grade:
Related Products
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