Choosing seawater heat exchanger materials by alloy name alone is risky. Raw seawater contains chlorides, oxygen, organisms and solids; warm harbor water, chlorination and stagnant shutdowns can increase corrosion. The right choice must protect every wetted part while meeting heat duty, pressure-drop, cleaning and service-life requirements.
This guide compares common seawater heat exchanger tube materials. For other duties, see our heat exchanger material selection guide.
Which Heat Exchanger Parts Are Exposed to Seawater?
In a shell and tube heat exchanger, seawater is often considered for the tube side for easier inspection and cleaning. A resistant alloy may also be limited mainly to the smaller seawater circuit. This is not a fixed rule; pressure, fouling and flow can change the shell-side vs tube-side allocation.
Seawater may contact tubes, tubesheets, tube joints, channels, bonnets, covers, nozzles, gaskets and fasteners. These parts must form a compatible system. Resistant tubes joined to an unsuitable tubesheet do not create a seawater-resistant exchanger.
A marine box cooler has different exposure: closed-loop coolant flows inside the bundle while seawater contacts the outside tube surface in the sea chest.
Titanium vs Copper-Nickel vs Duplex Stainless Steel
| Material | Common Selection Direction | Main Caution |
|---|---|---|
| Titanium Grade 2 | Severe or chlorinated seawater and long-life projects | Higher cost; fabrication, joints and galvanic compatibility need review |
| 90/10 Cu-Ni, C70600 | Flowing natural seawater and marine cooling | Protective-film formation matters; high local velocity, sulfides and polluted water increase risk |
| 70/30 Cu-Ni, C71500 | Duties needing greater strength and erosion margin | Higher cost; not automatically better for every system |
| Duplex 2205 | Selected chloride services requiring more strength than 316L | Not universally suitable for raw seawater; temperature, crevices and weld quality matter |
| Super Duplex 2507 | Aggressive chloride or offshore service | Welding, heat treatment, inspection and cathodic-protection interaction are critical |
| 316L Stainless Steel | Controlled, lower-chloride or indirect cooling | Pitting and crevice-corrosion risk in raw seawater, especially when warm, stagnant or chlorinated |
These are screening directions, not final approvals. A titanium heat exchanger for seawater may provide high corrosion resistance, while a copper nickel heat exchanger can offer better lifecycle value in suitable marine water. Duplex stainless steel in seawater must be checked against the actual environment and fabrication route.
A naval engineering review identifies corrosion and fouling as the main disadvantages of seawater cooling and concludes that selection depends on the environment and application. Therefore, “best material” without project data is not an engineering answer.
Which Seawater Conditions Change Material Performance?
Material review should cover:
- Water source and chemistry: open sea, harbor or brackish water; salinity, chloride, pH, sulfides, ammonia and solids.
- Operating envelope: normal and maximum temperature, flow, velocity, pressure and allowable pressure drop.
- Treatment and operation: chlorination, other biocides, continuous or intermittent service, stagnation, flushing and layup.
- Fouling and maintenance: organisms, sediment, cleaning chemicals and mechanical access.
- System details: all wetted materials, coatings, cathodic protection, design life, codes and failure history.
Higher velocity is not always better. Low flow may encourage deposits, while excessive local turbulence can damage protective films on some copper alloys. An expensive alloy also cannot correct incompatible joints, severe crevices or unsuitable cleaning chemicals.
Send Your Seawater Heat Exchanger Requirements to JED
JED manufactures custom marine heat exchangers, shell and tube units and box coolers from approved drawings or confirmed project data. We source specified materials and fabricate components to agreed construction, connection, inspection and testing requirements. Availability and manufacturing scope are confirmed before quotation.
Send your water analysis, operating data, drawing, required cooling duty and any existing-unit or failure information for review.
Frequently Asked Questions About Seawater Heat Exchanger Materials
Can only the seawater-side tube bundle be replaced?
Possibly. The existing shell, tubesheet interface, sealing surfaces, dimensions and pressure condition must first be checked. The replacement should also address the original cause of corrosion or leakage.
Can the material be changed without changing the existing connections?
Sometimes. Tube size, wall thickness, tubesheet, joint design, thermal expansion, galvanic compatibility, performance and applicable codes must be reviewed before retaining the same interfaces.
What material documents can buyers request?
Depending on the agreed scope, buyers may request material certificates, heat-number traceability, dimensional records, pressure or leakage test reports, and specified VT, UT, PT or third-party inspection documents.
What if the original material grade is unknown?
Start with the nameplate, drawings, maintenance records and photographs. PMI or laboratory testing may be required where the grade affects safety or corrosion resistance. Appearance alone is not reliable.
