Best Metals for Marine Environments and Saltwater Use

Saltwater can turn a small material-selection error into premature corrosion, recurring maintenance, or component failure. Selecting the best metal for saltwater applications is not always straightforward. Marine engineers and procurement teams must consider how the material will respond to immersion, flowing seawater, salt spray, and mechanical loading. 

Copper-based corrosion-resistant alloys offer several strong options for marine applications, from cooling systems to shipboard hardware.

What Makes a Metal Suitable for Marine Use?

The term “marine grade” is useful shorthand, but it does not identify a single specification. Marine-grade metals must maintain resistance to corrosion under the conditions defined for the project.

Saltwater exposure can cause general surface attack or more localized damage. Crevice corrosion may develop in shielded areas where stagnant saltwater creates different conditions from the surrounding water. Flow velocity is also a factor because fast-moving water can damage protective surface films. Even corrosion-resistant metals must be matched to the water chemistry and operating conditions.

Relative strength is a general comparison. Mechanical properties vary by product form and temper.

Copper-Nickel for Direct Seawater Service

For systems that carry seawater, copper-nickel is often the best metal for saltwater piping and cooling equipment. These alloys form a protective surface film that supports long-term performance. They also resist marine biofouling, although they cannot prevent all organism growth under every condition.

• C70600, or 90-10 copper-nickel: Combines excellent seawater-corrosion resistance with moderate strength and good ductility. Common uses include piping, heat-exchanger tubing, condensers, and desalination equipment.
• C71500, or 70-30 copper-nickel: Contains more nickel and generally provides higher strength. It is associated with demanding heat exchangers, pump parts, and seawater valves. Its lower thermal conductivity and potentially higher cost must be weighed against the added mechanical performance.

Neither alloy is immune to poor operating conditions. Polluted water, excessive flow velocity, or improper commissioning can interfere with protective-film development and reduce service life.

Naval Brass for Hardware and Plate Components

Among brass alloys, naval brass C46400 (listed as Alloy 464) is a strong option for hardware and plate components. This marine-grade brass uses a copper-zinc-tin composition that provides good strength and improved resistance to saltwater attack.

• Corrosion performance: The tin content increases resistance to dezincification compared with similar copper-zinc alloys that lack tin.
• Common applications: This brass alloy is used for fasteners, shipboard hardware, valve components, mounting plates, and selected heat-transfer equipment.
• Available forms: Lewis Brass & Copper supplies C46400 sheet and plate for marine and industrial use.

For hardware and plate applications, naval brass may be the best metal for saltwater environments when copper-nickel is unnecessary or unavailable in the required form.

Commercial Bronze, Muntz Metal, and Copper

Several other copper-based materials can perform well in selected marine environments:

• C22000 commercial bronze (listed as Alloy 220): Technically a high-copper brass containing about 90% copper. It provides good corrosion resistance, moderate strength, and excellent formability. Lewis Brass & Copper offers it as round tubing and sheet or plate.
• C28000 Muntz metal (listed as Alloy 280): Contains about 40% zinc, compared with roughly 10% in C22000. This higher zinc content generally provides greater strength and hardness. Applications include marine hardware, condenser plates, and above-water components. Lewis Brass & Copper supplies sheet or plate and several tubing profiles.
• C51000 phosphor bronze: A true bronze alloy available from Lewis Brass & Copper in coil form. Its fatigue and wear performance can suit fasteners, springs, or flexible components, but it is not a direct replacement for copper-nickel piping.
• Copper: Provides excellent thermal and electrical conductivity for grounding components, bonding systems, and lower-load heat-transfer equipment. Its mechanical strength is lower than that of the copper alloys discussed above.

The selected grade should match the expected saltwater exposure and mechanical load.

Other High-Performance Marine Metals

Some severe-service systems use Grade 2 titanium or nickel-copper Alloy 400 (Monel 400). Titanium provides exceptional resistance to seawater corrosion and is used in piping and heat exchangers, although crevice conditions require careful evaluation. Alloy 400 combines high strength with very low corrosion rates in flowing seawater, which suits pumps, valves, and shafting. Stagnant water can still promote localized attack.

Select the Alloy for the Actual Service Conditions

Selecting saltwater-resistant metals begins with defining the exposure. Material installed near the shoreline does not face the same conditions as tubing that carries seawater continuously. Water chemistry and flow velocity can influence corrosion behavior, while the design load determines the required strength. Compatibility with adjoining components and access for future inspection should also inform the decision. Product form and temper can then be matched to the project specifications.

Lewis Brass & Copper supplies copper-based tubing and pipe as well as rod and bar. Our inventory also includes coil, sheet, plate, and specialty shapes. We can provide material-application assistance based on your stated requirements. If a standard inventory item does not meet the project specifications, we can also help source non-stock alloys through our mill network.

Contact us to discuss the alloy, dimensions, and service conditions for your marine application.