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Admiralty brass vs Navel Brass, which one is best for Sea water Application?

For seawater application, especially in critical heat exchanger tubes, Admiralty Brass is generally the superior and more reliable choice. Naval Brass is better suited for shafts, valves, and fasteners.

Here’s a detailed breakdown of why:

Key Differences at a
Glance

Property	Admiralty Brass (UNS C44300)	Naval Brass (UNS C46400)
Primary Composition	71% Cu, 28% Zn, 1% Sn, 0.06% As	60% Cu, 39.2% Zn, 0.8% Sn
Also Known As	Admiralty Metal, C443	Naval Bronze, Tobin Bronze
Key Additive	Arsenic (As) and Tin (Sn)	Tin (Sn)
Best For	Heat Exchanger Tubes, Condenser Tubes	Shafts, Valves, Pump Parts, Fasteners
Major Weakness	Susceptible to dezincification if water conditions are poor/static.	Highly susceptible to dezincification in seawater.
Corrosion Resistance	Good to Excellent (with inhibitors). Better than Naval Brass.	Fair to Poor in seawater. Prone to rapid failure.
Mechanical Strength	Good	Very High (Higher tensile and yield strength)
Cost	Moderate	Moderate

 

Detailed Analysis

. Admiralty Brass (UNS C44300)

• Why it’s good for seawater: The small addition of Tin (Sn) improves its corrosion resistance. The critical addition is Arsenic (As), which acts as a potent inhibitor to dezincification.
• Dezincification: This is a selective leaching process where zinc is corroded out of the brass alloy, leaving behind a porous, weak copper structure. Admiralty Brass’s arsenic content dramatically slows this process down, making it “inhibited.”
• Application: It was the historical standard for seawater heat exchanger and condenser tubes for decades. It performs well in clean, flowing seawater where its protective film remains stable. It also has good biofouling resistance.
• The Caveat: Even with inhibitors, it can still suffer from dezincification in stagnant, polluted, or high-chloride waters. For this reason, it has been largely superseded by more robust alloys like 90/10 Copper-Nickel (C70600) and 70/30 Copper-Nickel (C71500) in modern marine applications.

2. Naval Brass (UNS C46400)

• Why it’s named “Naval”: The name comes from its excellent mechanical properties (high strength, good wear resistance, and excellent hot workability), not its corrosion resistance. It was historically used for marine hardware that required strength.
• Poor Seawater Corrosion Resistance: Despite its name, Naval Brass has very poor resistance to dezincification in seawater. It lacks the arsenic inhibitor found in Admiralty Brass. Using it as a tube in a heat exchanger exposed to seawater would be a recipe for rapid failure.
• Application: Its use is almost exclusively for structural and mechanical components in marine environments, such as:
  • propeller shafts
  • pump parts
  • valve stems and trim
  • nuts, bolts, and other fasteners
  • hardware

Which One is “Best”?

Admiralty brass vs Navel Brass, which one is best for Sea water Application?     For seawater application, especially in critical heat exchanger tubes, Admiralty Brass is generally the superior and more reliable choice. Naval Brass is better suited for shafts, valves, and fasteners. Here’s a detailed breakdown of why: Key Differences at a Glance Property Admiralty Brass (UNS C44300) Naval Brass (UNS C46400) Primary Composition 71% Cu, 28% Zn, 1% Sn, 0.06% As 60% Cu, 39.2% Zn, 0.8% Sn Also Known As Admiralty Metal, C443 Naval Bronze, Tobin Bronze Key Additive Arsenic (As) and Tin (Sn) Tin (Sn) Best For Heat Exchanger Tubes, Condenser Tubes Shafts, Valves, Pump Parts, Fasteners Major Weakness Susceptible to dezincification if water conditions are poor/static. Highly susceptible to dezincification in seawater. Corrosion Resistance Good to Excellent (with inhibitors). Better than Naval Brass. Fair to Poor in seawater. Prone to rapid failure. Mechanical Strength Good Very High (Higher tensile and yield strength) Cost Moderate Moderate   Detailed Analysis 1. Admiralty Brass (UNS C44300) Why it’s good for seawater: The small addition of Tin (Sn) improves its corrosion resistance. The critical addition is Arsenic (As), which acts as a potent inhibitor to dezincification.Dezincification: This is a selective leaching process where zinc is corroded out of the brass alloy, leaving behind a porous, weak copper structure. Admiralty Brass’s arsenic content dramatically slows this process down, making it “inhibited.”Application: It was the historical standard for seawater heat exchanger and condenser tubes for decades. It performs well in clean, flowing seawater where its protective film remains stable. It also has good biofouling resistance.The Caveat: Even with inhibitors, it can still suffer from dezincification in stagnant, polluted, or high-chloride waters. For this reason, it has been largely superseded by more robust alloys like 90/10 Copper-Nickel (C70600) and 70/30 Copper-Nickel (C71500) in modern marine applications. 2. Naval Brass (UNS C46400) Why it’s named “Naval”: The name comes from its excellent mechanical properties (high strength, good wear resistance, and excellent hot workability), not its corrosion resistance. It was historically used for marine hardware that required strength.Poor Seawater Corrosion Resistance: Despite its name, Naval Brass has very poor resistance to dezincification in seawater. It lacks the arsenic inhibitor found in Admiralty Brass. Using it as a tube in a heat exchanger exposed to seawater would be a recipe for rapid failure.Application: Its use is almost exclusively for structural and mechanical components in marine environments, such as:propeller shaftspump partsvalve stems and trimnuts, bolts, and other fastenershardware Which One is “Best”? The answer depends entirely on the application: Your application Recommended Material Reason Heat Exchanger / Condenser Tubes Admiralty Brass (C44300) is acceptable, but 90/10 CuNi (C70600) is vastly superior and the modern standard. Admiralty resists dezincification enough for some applications, but CuNi is more reliable and durable long-term. Naval Brass is a terrible choice here. Pump Shafts, Valve Stems, Fasteners Naval Brass (C46400) is an excellent choice. Its high strength and wear resistance are the priority. Corrosion is managed through proper sizing (allowing for wear down) and maintenance. General Marine Hardware Naval Brass (C46400) is the standard. It offers the best combination of strength, machinability, and adequate corrosion resistance for non-immersion or non-heat-exchange applications. For a seawater application involving heat transfer under flow (like an oil cooler tube), Admiralty Brass is definitively better than Naval Brass. However, for a long-life, reliable system, 90/10 Copper-Nickel is the best common choice. Reserve Naval Brass for strong, corrosion-resistant mechanical parts, but never for heat exchanger tubes carrying seawater.