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Duplex vs SS316 for Chloride and Seawater
Updated 2026-10-30 · Supreme Valves India Engineering
Selection rule
CF8M / SS316 remains the default stainless for mild chemicals and low chlorides. Duplex 2205 raises PREN and strength for warm chlorides, brackish water, and duplex pipe classes.
Seawater often competes with NAB C95800 and super duplex — see the linked comparisons before forcing duplex on every seawater line.
Valve types commonly upgraded
Gate and globe for isolation / throttle on chloride process.
Ball valves Class 150–600 where fire-safe hydrocarbon meets chlorides.
Butterfly PN10/PN16 for large-bore water with chlorides.
Check valves on pump discharge in corrosive water.
FAQ
Is duplex always better than 316?
No — only when corrosion data or pipe class requires higher PREN / strength.
Cast or wrought duplex?
Cast A995 4A for bodies; wrought F51 for forged / bar. Confirm grade on the RFQ.