What Are The Common Materials Used in Marine Bearing Oil Coolers?

Material selection for marine bearing oil coolers is governed by three strict marine requirements: seawater corrosion resistance, anti-biofouling performance, galvanic corrosion compatibility, and thermal conductivity. Components are split into heat transfer tubes, tube sheets, water headers, shell bodies, support structures, and sealing gaskets, with dedicated marine-grade materials for each part. Below is a full classification, application scenarios, pros & cons, and matching rules.

CuNi 90/10 (C70600, 90 Copper + 10 Nickel) – Global Standard Marine Tube

- Composition: 90% Cu, 10% Ni, trace iron and manganese

- Advantages:

1. High thermal conductivity, far superior to stainless steel and titanium; stable heat exchange efficiency under long-term operation.

2. Natural anti-fouling property: copper ions inhibit barnacles, algae and marine organisms from adhering to tube inner walls, cutting cleaning frequency.

3. Excellent resistance to pitting and crevice corrosion in normal ocean seawater, brackish coastal water, and estuary water.

4. Balanced cost and performance, easy tube bending for U-tube bundles, good ductility for tube expansion welding.

- Applicable working conditions: Most ocean-going cargo ships, tankers, tugboats, fishing vessels, marine steam/gas turbine bearing coolers; seawater flow velocity 1.0–2.5 m/s.

- Disadvantage: Slightly weaker erosion resistance under high-speed sediment-laden seawater than CuNi 70/30.

CuNi 70/30 (C71500, 70 Copper + 30 Nickel) – Heavy-Duty Harsh Sea Grade

- Composition: 70% Cu, 30% Ni

- Advantages:

1. Higher nickel content delivers stronger resistance to high-velocity seawater erosion, sulfur-containing polluted seawater, and sediment abrasion.

2. Outstanding anti-stress corrosion and cavitation resistance, suitable for offshore platforms, fast vessels, and river-sea dual-purpose ships.

3. Longer service life in tropical, high-salinity sea areas.

- Disadvantage: Higher material cost than 90/10 copper nickel.

Aluminum Brass (CuZn20Al) – Economy Light-Duty Option

- Composition: Copper-zinc base with aluminum anti-corrosion additive

- Advantages: Low raw material cost, good thermal conductivity, easy processing.

- Limitations:

Poor resistance to polluted, sulfur-rich seawater; prone to dezincification corrosion after 3–5 years of continuous navigation.

- Application: Small yachts, inland fishing boats, short-distance coastal vessels with clean seawater intake. Not recommended for ocean-going main engine bearing coolers.

316L / Duplex Stainless Steel (2205) – Rare Auxiliary Special Scenarios

- 316L SS: Resists weak acid corrosion, but poor anti-biofouling performance; severe barnacle accumulation blocks tubes within months. Low thermal conductivity requires larger tube bundles, rarely used for seawater side. Only used for fresh water cooling circuits on closed-loop vessels.

- Duplex 2205: Better seawater corrosion resistance than 316L, high mechanical strength, but expensive, low heat transfer efficiency; limited to chemical tanker closed fresh water cooling systems.

Titanium Grade 2 – Ultra-Corrosive Extreme Working Condition

- Advantages: Fully resistant to high-salinity, chemical-polluted seawater, acid/alkaline sewage on chemical tankers. Zero pitting corrosion.

- Disadvantages: Extremely high material cost, low thermal conductivity (needs extra fin enhancement), difficult tube expansion processing.

- Application: Special chemical carriers, offshore chemical processing platforms with heavily contaminated cooling water.