Seawater, desalination, offshore – pipes for chloride media
In short: in seawater and brine, conventional stainless steel is prone to pitting and crevice corrosion. Typical choices for these systems:
- duplex: 1.4462 (S31803 / S32205);
- super duplex: 1.4410 (S32750), 1.4501 (S32760);
- titanium: for the most demanding cases.
Fittings and flanges come from the same material family (ASTM A815 fittings; F51, F53, F55 flanges).
This guide is for buyers at desalination plants, marine and offshore facilities and industrial brine-cooling systems.
Why are chloride media difficult?
- Pitting and crevice corrosion. Chloride ions break through the passive layer of stainless steel locally.
- Stress-corrosion cracking at higher temperatures.
- Temperature and flow. Warm and stagnant seawater is especially aggressive.
The higher chromium, molybdenum and nitrogen content of duplex and super duplex steels gives better resistance. This is expressed by the pitting resistance equivalent number (PREN).
Material overview
| Situation | Typical material |
|---|---|
| Brine cooling, moderate chloride load | 1.4462 (duplex) |
| Seawater, desalination high-pressure lines | 1.4410, 1.4501 (super duplex) |
| Most demanding seawater systems | Titanium Grade 2 |
The designer selects the final material from chloride content, temperature and flow conditions.
The complete package
- Pipes: ASTM A790, EN 10216-5 / EN 10217-7.
- Fittings: ASTM A815.
- Flanges: F51, F53, F55.
- Bolting: duplex or super duplex fasteners.
- Gaskets for the medium.
- Valves with duplex or stainless bodies.
Buyer checklist
- Grade with EN and UNS number.
- Size and rating.
- Fitting and flange material from the same family.
- Bolting material.
- Testing: e.g. corrosion test, ferrite content, if specified.
- Certificate: 3.1 or 3.2.
Common mistakes
- Duplex pipe with 316L fittings or flanges, which creates the weakest point.
- Carbon-steel bolts in a marine environment.
- Test requirements missing from the order.
Frequently asked questions
What is the difference between duplex and super duplex?
Super duplex is more highly alloyed, so it resists more aggressive chloride media. It is typically specified for seawater and desalination.
Do you supply titanium pipe?
Yes, titanium pipes, fittings and flanges.
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Send your material list and medium data. We quote the duplex, super duplex or titanium line in one offer, with matched materials.
Related: Duplex, nickel alloys, titanium · 1.4462 · 1.4410 · Chemical guide
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