Admiralty brass and aluminium brass are two of the most widely used copper alloys for condenser and heat-exchanger tubes. They look alike, they are both brass, and they are often listed side by side in the same specification. Yet they behave differently in service, and choosing the wrong one can shorten tube life considerably. This guide explains how the two alloys differ and how to match each one to your cooling-water conditions.
What Is Admiralty Brass?
Admiralty brass is a copper-zinc alloy containing roughly 70 percent copper, 29 percent zinc and about 1 percent tin. The tin improves corrosion resistance compared with plain brass. A small addition of an inhibitor such as arsenic, antimony or phosphorus is normally made to reduce dezincification, a form of corrosion in which zinc is selectively leached out and leaves a weak, porous copper structure. These inhibited versions are listed in standards under designations such as C44300, C44400 and C44500.
Admiralty brass has been used for condensers for well over a century. It performs well in fresh, clean and mildly brackish cooling water at moderate velocities. You can read more about this alloy on our admiralty brass tubes page.
What Is Aluminium Brass?
Aluminium brass contains roughly 76 percent copper, 22 percent zinc and about 2 percent aluminium, again with a small arsenic addition to guard against dezincification (designation C68700). The aluminium helps the alloy form a thin, tenacious protective film on the tube surface. That film is what gives aluminium brass its better resistance to erosion-corrosion, particularly in seawater and in water carrying sand or suspended solids at higher velocities.
Because of this, aluminium brass is a staple for seawater-cooled condensers, desalination plant heat exchangers and ship’s cooling systems. See our aluminium brass tubes page for the sizes we manufacture.
Side-by-Side Comparison
- Composition: admiralty brass is copper, zinc and tin; aluminium brass is copper, zinc and aluminium.
- Seawater and brackish water: aluminium brass generally performs better and tolerates higher flow velocities.
- Fresh and clean cooling water: admiralty brass is a proven and economical choice.
- Erosion-corrosion resistance: aluminium brass is stronger in this respect.
- Sensitivity to polluted water: both alloys can suffer in water containing sulphides or ammonia, so water quality must be assessed.
- Cost: prices follow metal costs and size; the better fit usually matters more than the small price difference.
Water Quality Decides the Choice
The single most important input is the cooling water itself. Ask these questions before selecting an alloy:
- Is the water fresh, brackish or full seawater?
- What flow velocity will the tubes see?
- Does the water carry sand, silt or other suspended solids?
- Is there any risk of sulphide or ammonia contamination, for example in polluted harbours or estuaries?
- How long must the tubes last, and how easy is retubing?
If the water is heavily polluted, or the velocity is high and the service critical, you may need to step up to cupro nickel. Our article 90/10 vs 70/30 cupro nickel explains when that upgrade is worthwhile, and our material selection guide compares copper, cupro nickel and brass.
Standards and Documentation
Both alloys are covered by ASTM B111, which sets chemical composition, mechanical properties, dimensions and test requirements for copper and copper-alloy condenser and heat-exchanger tube. Read our buyer’s guide to ASTM B111 for a plain-language walkthrough. Whatever alloy you buy, insist on a mill test certificate so that composition and heat number can be verified against your order.
Installation Tips That Protect Tube Life
- Keep tube-side velocity within the supplier’s recommended range to avoid erosion at tube inlets.
- Use correctly sized tube-sheet holes and expansion to avoid leaks and crevice corrosion.
- Flush and pre-film new tubes with clean water where recommended, so the protective film forms evenly.
- Avoid long idle periods with stagnant, untreated water inside the tubes.
Common Mistakes When Specifying Brass Tubes
Three errors appear again and again in enquiries. First, buyers list “brass tube” without naming the alloy, which leaves the supplier to guess. Second, the water analysis is never shared, so the alloy is chosen on price alone. Third, the velocity and operating temperature are left out, even though both strongly influence erosion and corrosion rates. Giving your supplier complete operating data takes only a few minutes and can add years to the life of a tube bundle.
Frequently Asked Questions
Which is better in seawater, aluminium brass or admiralty brass?
Aluminium brass is generally preferred for seawater and higher velocities because of its better resistance to erosion-corrosion.
Can admiralty brass be used in desalination plants?
It can be used in some brackish or less demanding stages, but aluminium brass or cupro nickel is more common for seawater service. See our guide to alloy selection for desalination plants.
What does dezincification mean?
It is the selective loss of zinc from brass, leaving a weak copper-rich structure. Small inhibitor additions such as arsenic help prevent it.
Talk to Our Technical Team
Jaydeep Tubes manufactures both alloys at our Umbergaon plant and supplies customers across India and the Gulf. Share your water analysis, tube size and quantity and we will recommend the most suitable grade. Contact us for a quotation.