Copper-Nickel Alloy Tubing for Marine & Ship-building Works

● GB/T26291             MIL-T-16420K(SH)                  ASTM B167/167M

● DIN86019              EN/BS2871                         EEMUA144/234

Copper-nickel alloys (primarily 90-10 Cu-Ni and 70-30 Cu-Ni) are essential materials in marine engineering and shipbuilding due to their unique combination of corrosion resistance, anti-fouling properties, and mechanical durability in seawater environments. Below are the key reasons for their widespread use:

Problem with Other Metals:

● Carbon steel rusts rapidly in seawater, requiring expensive coatings and cathodic protection.

● Stainless steel (316L, duplex) can suffer from pitting and crevice corrosion in chloride-rich seawater.

● Aluminum is prone to galvanic corrosion when coupled with other metals.

Why Cu-Ni Excels:

✔ Forms a protective oxide layer that resists saltwater corrosion, erosion, and cavitation damage.

✔ Highly resistant to biofouling (discussed next).

✔ Performs well in both flowing and stagnant seawater (unlike stainless steel, which needs oxygen to maintain its passive layer).

Problem with Biofouling in Marine Environments:

● Marine organisms (barnacles, algae, mussels) attach to ship hulls and pipes, causing:

● Increased drag → Higher fuel consumption (up to 40% more!)

● Blocked cooling systems → Overheating & maintenance costs

● Microbial-induced corrosion (MIC) → Premature failures

Why Cu-Ni is the Best Choice:

✔ Copper ions (Cu²⁺) leach slowly from the alloy, killing marine organisms and preventing attachment.

✔ Eliminates the need for toxic antifouling paints (which are being banned due to environmental regulations).

✔ Self-healing surface—even if scratched, the oxide layer reforms, maintaining protection.

→ Ships using Cu-Ni hulls or piping report up to 30% less fuel consumption due to reduced drag!

Problem in Marine Systems:

● High-velocity seawater (e.g., in pumps, propellers, condensers) causes erosion-corrosion in carbon steel and even stainless steel.

● Cavitation (bubble implosion) damages metal surfaces over time.

Why Cu-Ni Performs Better:

✔ High toughness and work-hardening ability resist wear in turbulent flow.

✔ 70-30 Cu-Ni is especially durable in seawater piping, propeller shafts, and heat exchangers.

Problem with Mixed-Metal Systems:

Stainless steel + aluminum or carbon steel + bronze can create galvanic corrosion in seawater.

Why Cu-Ni is Safe:

✔ Moderate electrochemical potential—can be safely used with stainless steel, bronze, and titanium without severe galvanic corrosion.

✔ Used in condenser tubes, seawater piping, and heat exchangers without isolation flanges.

Problem with Traditional Materials:

● Carbon steel pipes in seawater last 5-10 years before replacement.

● Stainless steel (316L) may last 15-20 years but requires frequent cleaning to prevent bio-fouling.

Why Cu-Ni is Cost-Effective Long-Term:

✔ 50+ year lifespan in seawater with minimal maintenance.

✔ No need for:

● Cathodic protection (unlike carbon steel)

● Chlorination/biocides (unlike stainless steel)

● Anti-fouling coatings (unlike aluminum/steel hulls)

→ Despite higher upfront cost, Cu-Ni reduces life-cycle costs by 50%+ compared to carbon steel.

Stricter environmental laws banning toxic anti-fouling paints (e.g., TBT-based coatings).

Fuel efficiency regulations pushing for bio-fouling-resistant hulls.

Growth in offshore wind & desalination, where Cu-Ni is used in critical seawater systems.

Conclusion

Copper-nickel alloys are indispensable in marine and shipbuilding because they:

✅ Resist seawater corrosion & bio-fouling naturally.

✅ Reduce fuel costs by keeping hulls/pipes clean.

✅ Last 50+ years with minimal maintenance.

✅ Are environmentally friendly (no toxic coatings needed).

While stainless steel and carbon steel still have their uses, Cu-Ni is the best choice for seawater applications where longevity and efficiency matter most.