C68700 – Aluminum brass – CuZn22AL2
Strong corrosion resistance makes this alloy excellent for use with high cooling water velocities.
C68700 aluminum brass is a copper-zinc alloy enhanced with aluminum and a corrosion inhibitor to deliver exceptional resistance to high-velocity seawater and brackish water. Known for its strength and durability, this alloy is engineered to withstand impingement attack and erosion-corrosion in aggressive cooling environments.
Inhibited aluminum brass tubes (C68700) are widely used in condenser systems, especially in marine, power generation, and desalination settings, where water velocity and salt content challenge the long-term performance of standard copper alloys.
Applications
C68700 aluminum brass tubes are commonly used in:
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Condenser tubes for high-velocity cooling water
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Seawater cooling systems in marine and offshore applications
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Power station condensers (marine and land-based)
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Desalination plants and saltwater treatment facilities
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Heat exchangers exposed to turbulent or contaminated water
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Industrial cooling systems with brackish or saline water circulation
Key benefits
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Exceptional resistance to impingement and erosion: handles high-velocity water without thinning or surface degradation.
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Superior corrosion resistance in salt and brackish water: aluminum content and inhibitors protect against pitting, dezincification, and scaling.
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Reliable performance in marine and industrial settings: maintains mechanical integrity even under fluctuating thermal loads and flow conditions.
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High thermal conductivity for effective heat transfer: ensures energy-efficient operation in demanding cooling applications.
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Extended service life: reduces maintenance costs and unplanned downtime in critical systems.
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Compliance with international standards: manufactured to meet ASTM B111 and other global specifications.
Technical specifications
SB 111, SB 395
Properties and metrics
Properties *
Metric
English
Density
8.33 g/cc
0.301 lb/in³
Tensile strength
345 MPa
50 ksi
Yield strength
125MPa
18 ksi
CTE, linear
18.5 10-6/°C @ 20 – 300°C
10.3 10-6/°F @ 70 – 570°F
Specific heat capacity
0.09 cal/g-°C @ 20ºC
0.09 BTU/lb-°F @ 70ºF
Thermal conductivity
100.4 W/m-K @ 20°C
58 BTU/ft2/ft/h/°F @ 70°F
Melting point
932 ~ 971°C
1710 ~ 1780°F
* The information provided on this page includes typical values which are only for general reference and information. These values are not intended for exact specification, design or engineering purposes.
Frequently asked questions about aluminum brass
What is aluminum brass used for?
Aluminum brass tubes are used in condensers and heat exchangers cooled by seawater or brackish water, mainly in power stations, desalination plants, ships, offshore platforms and refineries. The alloy resists impingement and erosion-corrosion at higher water velocities than admiralty brass.
What does aluminum do in aluminum brass?
The 1.8–2.5% aluminum forms a thin, self-healing aluminum oxide film on the tube surface. The film protects the alloy from impingement attack and erosion-corrosion in fast-flowing seawater. The arsenic addition (0.02–0.06%) inhibits dezincification.
What is the difference between aluminum brass and admiralty brass?
Aluminum brass (C68700) contains aluminum and handles faster, more turbulent seawater. Admiralty brass (C44300) contains about 1% tin and suits cleaner or freshwater cooling at lower velocities. For seawater condensers, aluminum brass is usually the better specification.
What water velocity can aluminum brass tubes handle?
A commonly used design limit for aluminum brass condenser tubes is about 2.4 m/s (8 ft/s), compared with about 1.8 m/s for admiralty brass. Where velocities are higher, 90-10 or 70-30 copper-nickel is normally specified.
Is aluminum brass the same as aluminum bronze?
No. Aluminum brass is a copper-zinc alloy with about 2% aluminum, used mainly for condenser tubes. Aluminum bronze is a copper-aluminum alloy with roughly 5–12% aluminum and little or no zinc, used for high-strength castings, bearings and marine hardware.
Which ASTM and ASME specifications cover C68700 tubes?
Seamless C68700 condenser and heat exchanger tubes are covered by ASTM B111 / ASME SB111. U-bend tubes are covered by ASTM B395 / ASME SB395. Tubes are typically supplied in the O61 annealed temper.
When should I choose copper-nickel instead of aluminum brass?
Choose 90-10 (C70600) or 70-30 (C71500) copper-nickel when cooling water velocities exceed the aluminum brass limit, when the water carries entrained sand, or when a longer service life justifies the higher cost. Aluminum brass is also unsuitable where ammonia is present, because brasses are prone to stress corrosion cracking in ammonia.
Does Admiralty Industries supply C68700 aluminum brass tubes?
Yes. Admiralty Industries supplies C68700 aluminum brass condenser and heat exchanger tubes to ASTM B111 / ASME SB111, including U-bends to B395. Contact us with your size, quantity and specification for a quote.
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