C44300 is the UNS designation of the arsenical admiralty brass that heat exchanger designers specify when tubes have to survive cooling water that is fresh, brackish or salty. The alloy is a single-phase copper-zinc alpha brass containing about 71 % copper, 1 % tin and a deliberate addition of 0.02 - 0.06 % arsenic, and it is produced as seamless tubing to ASTM B111/B111M for condensers, evaporators and similar heat transfer equipment. This guide describes the composition, equivalent specifications, physical and mechanical properties, supply sizes and corrosion behaviour of C44300 tubes for heat exchange systems.
Why Admiralty Brass Is Used in Heat Exchangers
Three properties make C44300 a default tube material for water-cooled exchangers. The first is thermal conductivity, which is an order of magnitude higher than stainless steel, so tube wall resistance contributes little to overall heat transfer. The second is the tin addition, which strengthens the alloy modestly and improves resistance to flowing water, while the arsenic addition suppresses the selective loss of zinc known as dezincification. The third is fabrication economics: seamless tube of high quality is produced by cold drawing and re-drawing, giving tight wall tolerance, good concentricity and a surface that stays clean in service. Admiralty brass has been used in condensers for more than a century, and its behaviour in cooling water circuits is well documented.
Equivalent Specifications and Designations
| Category | ASTM / UNS | Other systems |
|---|---|---|
| Admiralty brass (arsenical) | C44300 | EN CW706R, CuZn28Sn1As |
| DIN | 2.0470 | CuZn28Sn1As |
| BS | CZ111 | Admiralty brass tube grades |
| JIS | C4430 | JIS H3100 / H3300 series |
| ISO | CuZn28Sn1 | Wrought copper alloy |
| GB (China) | HSn70-1 | Equivalent wrought composition |
| IS (India) | CuZn29Sn1As | IS 1545 piping grades |
Seamless tube is ordered to ASTM B111/B111M or to the identical ASME SB111 specification, which fixes the composition, the temper, the dimensional tolerances and the mechanical test requirements. Water-side tube selection for a specific exchanger also refers to TEMA practice and to the fouling and velocity limits of the cooling circuit.
Chemical Composition of C44300 Tube
| Element | Range, % by weight | Nominal |
|---|---|---|
| Copper (Cu) | 70.0 - 73.0 | 71.0 |
| Tin (Sn) | 0.8 - 1.2 | 1.0 |
| Arsenic (As) | 0.02 - 0.06 | 0.04 |
| Lead (Pb) | 0.07 max | - |
| Iron (Fe) | 0.06 max | - |
| Zinc (Zn) | Remainder | 28.0 |
The narrow arsenic window is the feature that distinguishes an inhibited admiralty brass from a plain 70/30 type composition. Arsenic is added at parts-per-hundred level and acts as a cathodic inhibitor that prevents the preferential dissolution of zinc; removing it turns the alloy back into a material that is vulnerable to plug-type dezincification in poorly aerated water.
Physical and Thermal Properties
| Property | Value |
|---|---|
| Density | 8.53 g/cm³ (0.308 lb/in³) |
| Melting range, solidus to liquidus | 899 - 938 °C (1650 - 1720 °F) |
| Specific gravity | 8.53 |
| Thermal conductivity at 20 °C | about 111 W/(m·K), equal to 64 Btu·ft/(hr·ft²·°F) |
| Electrical conductivity at 20 °C | 25 % IACS |
| Electrical resistivity at 20 °C | 41.5 ohm·circular mil/ft |
| Coefficient of thermal expansion | 20.2 µm/(m·°C), 11.2 µin/(in·°F), 20 - 300 °C |
| Modulus of elasticity in tension | 110 GPa (16000 ksi) |
| Modulus of rigidity | 41 GPa (6000 ksi) |
| Specific heat capacity | 377 J/(kg·K), 0.09 Btu/(lb·°F) |
Note on units: the low thermal resistance of this alloy is often mis-stated because the British thermal unit figure is quoted against the wrong length unit. The correct statement is 64 Btu·ft/(hr·ft²·°F), which converts to about 111 W/(m·K).
Mechanical Properties and Temper Selection
| Condition | Tensile strength | Remarks |
|---|---|---|
| Annealed, O61 | 310 MPa (45 ksi) minimum, typical | Fully softened for rolling into U-bends and expanding into tube sheets |
| Light drawn, H55 | 345 - 450 MPa typical | Higher strength at some loss of elongation |
| Drawn, H80 | 390 MPa minimum, typical | For straight lengths where stiffness and erosion resistance matter |
Elongation is temper dependent: annealed tube retains most of its ductility, while cold-drawn tempers trade elongation for tensile strength. For U-bend exchangers the tube is normally supplied in the annealed or lightly drawn condition so that bending does not crack the outer fibre, and the bend radius is standardised to the pitch of the tube sheet.
Supply Sizes and Other Forms
| Form | Range |
|---|---|
| Seamless tube, outside diameter | 6 - 159 mm |
| Seamless tube, wall thickness | 0.5 - 5 mm |
| Straight length | 1 - 6 m |
| Coiled length | up to 50 m |
| Hollow rod | bore from 20 mm, outside diameter to 100 mm |
| Round rod | 6 - 130 mm |
| Hexagon | 5 - 60 mm |
| Square | 4 - 60 mm |
| Flat bar | 5 mm minimum thickness, maximum width 120 mm |
| Billet | up to 200 mm |
Tubes are delivered in straight lengths for shell-and-tube bundles and in coils for feedwater heaters, aftercoolers and refrigeration circuits. Condenser tube plate material and ferrules are supplied as plate and bar from the same alloy family so that the whole water-side assembly has matching electrochemical behaviour.
Corrosion Behaviour in Cooling Water Service
C44300 performs well in fresh, brackish and salt water, and its arsenic content protects it against dezincification in stagnant or low-oxygen conditions. It is not immune to every mechanism: impingement attack and erosion-corrosion occur if water velocity is excessive or if the flow contains entrained sand, and sulphide-polluted water can accelerate attack on the protective film. In practical exchanger design the water velocity, the cleanliness of the tubes and the frequency of cleaning are therefore specified together with the tube alloy, not separately. Where cooling water is heavily polluted or contains ammonia, an alloy with higher copper-nickel content is usually selected instead.
Frequently Asked Questions
Q: What does the 44300 designation mean?
C44300 is the UNS number for wrought arsenical admiralty brass, a 71 % copper, 28 % zinc, 1 % tin alloy with 0.02 - 0.06 % arsenic added as a dezincification inhibitor.
Q: Which standard governs seamless C44300 heat exchanger tube?
ASTM B111/B111M in the United States and the identical ASME SB111 specification for pressure equipment, with EN 12451 or EN 12449 used for European heat exchanger and general-purpose tube orders.
Q: Why is arsenic added to admiralty brass?
Arsenic at 0.02 - 0.06 % acts as a cathodic inhibitor that prevents selective zinc loss. Without it the alloy suffers plug-type dezincification in slow-moving or poorly aerated water.
Q: Is C44300 the same as naval brass tubing?
No. C44300 is admiralty brass, with tin and arsenic as the inhibitive additions. Naval brass is a different family, typically C46400 or C46500, in which tin is added at around 0.75 % without arsenic and with a much higher zinc content.
Q: Can C44300 tubes be used in steam or hot-water service?
Yes. The alloy is commonly supplied for feedwater heaters, condensers and steam surface condensers, where the working temperature stays within the range for which admiralty brass retains its strength and its protective film.
Q: What tube tempers are available?
Annealed O61 for U-bend and expansion work, and light-drawn or drawn tempers such as H55 and H80 where higher tensile strength is required, all within the size and tolerance limits of ASTM B111.
