Aluminum Bronze
Aluminum bronze is copper with 5–11 % aluminum, usually plus iron and nickel. The aluminum forms a tough, self-healing oxide film that makes these the most corrosion-resistant copper alloys in seawater and acids, and the alloy is strong: nickel-aluminum bronze C63000 yields 345–415 MPa as extruded bar, about the level of a normalized medium-carbon steel, with a hardness around 200 HB that resists galling and cavitation. Grades above about 9 % aluminum are two-phase and can be quench-hardened, which is why the series is marked heat-treatable in part.
Popular aluminum bronze grades
Compare in the explorer| Grade | Yield, MPa | Tensile, MPa | Density, g/cm³ | Machinability | Weldability | Best for |
|---|---|---|---|---|---|---|
| C63000 | 415 | 760 | 7.58 | Poor | Good | Nickel-aluminum bronze shafts, bushings, valve trim |
| C64200 | 370 | 690 | 7.69 | Good | Very good | Machinable aluminum bronze for stems and nuts |
| C61400 | 230 | 525 | 7.89 | Poor | Very good | Weldable plate and sheet, tube sheets |
| C62300 | 290 | 585 | 7.65 | Fair | Very good | General bushings and gear bar |
| C63200 | 345 | 690 | 7.64 | Poor | Very good | Naval weldable nickel-aluminum bronze |
| C61300 | 275 | 550 | 7.89 | Poor | Very good | Tin-bearing weldable plate, pressure parts |
| C62400 | 310 | 660 | 7.45 | Poor | Good | Forming dies and hard wear parts |
Choose aluminum bronze for
Seawater pump shafts, impellers and valve trim, propeller and stern-tube hardware, heavy slow-speed bushings and wear plates, forming and deep-draw dies for stainless sheet, non-sparking and non-magnetic tools, and any copper-alloy part that must carry steel-like load without galling.
Look elsewhere when
The part is a light bushing with good lubrication (C93200 bearing bronze embeds dirt better and machines faster), it is turned in volume (C36000 brass or C64200), it must conduct (C18200 keeps 80 % IACS against 7 %), or the part sits in hot seawater and the grade is a nickel-free one above 9 % aluminum — dealuminification attacks C62300 and C62400 where C63000 and C63200 hold.
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Aluminum bronze by application
- Seawater shafts and pump parts
- C63000 bar and forgings for shafts, sleeves and wear rings; C63200 where the assembly is welded or the seawater is hot. Both resist cavitation and biofouling better than stainless.
- Heavy bushings and wear plates
- C63000 for the highest loads and shock, C62300 for general bushings, C62400 for slides and guide bushings running against hardened steel. Cast C95400 or C95500 when the bushing is large.
Working with aluminum bronze
- Machining
- Tough and abrasive: C63000 machines at about 30 % of C36000 with carbide, rigid setups and positive feed, and work-hardens if the tool rubs. C64200 doubles that rate. Chips are short; finishes are good; the alloy holds ±0.02 mm on bushings without trouble.
- Welding
- C61400, C61300 and C63200 TIG and MIG weld readily with ERCuAl-A2 or nickel-aluminum-bronze filler and little preheat. C63000 welds but needs care with heat input, and the 11 % plus grades used for dies are not welded. Repair welding of NAB castings is routine.
- Heat treatment
- C63000 and the cast C95400 and C95500 can be quench-and-tempered (TQ50: water quench from about 870 °C, temper at 600–650 °C) for roughly 20 % more strength and a finer, more corrosion-resistant structure. Lower-aluminum grades strengthen only by cold work. Anneal at 600–700 °C.
- Finishing
- Aluminum bronze is used bare; the oxide film is its protection. Do not electroplate without a special strike, since the aluminum oxide resists adhesion. A light passivation or oiling is enough for shipment.
Other copper alloy series
Aluminum Bronze — frequently asked
What is aluminum bronze?
Aluminum bronze is copper with 5–11 % aluminum, usually plus iron and nickel. The aluminum forms a tough, self-healing oxide film that makes these the most corrosion-resistant copper alloys in seawater and acids, and the alloy is strong: nickel-aluminum bronze C63000 yields 345–415 MPa as extruded bar, about the level of a normalized medium-carbon steel, with a hardness around 200 HB that resists galling and cavitation. Grades above about 9 % aluminum are two-phase and can be quench-hardened, which is why the series is marked heat-treatable in part.
Which grade of aluminum bronze should I use?
C63000 nickel-aluminum bronze for the loaded part — pump shafts, valve stems, wear rings, landing-gear and press bushings, marine fasteners. C63200 is the same family tuned for weldability and hot seawater, specified on naval drawings. C64200 (7 % Al, 2 % Si) when the part is mostly machined: valve stems, nuts, gears and pole-line hardware at twice the machinability of C63000. C61400 and C61300 (7 % Al, 2 % Fe) for sheet and plate that is welded — tube sheets, tanks, condenser parts. C62300 is the general-purpose bushing and gear bar; C62400 and C62500 go to 11–13 % aluminum for forming dies, guide bushings and drawing rings where hardness above 200 HB matters more than toughness. For castings, the family continues as C95400, C95500 and C95800.
Which grade of aluminum bronze is the strongest?
C63800 has the highest yield strength in the series at 855 MPa; C63020 follows at 725 MPa. Values are for each grade's default condition.
Which grade of aluminum bronze is easiest to machine?
C64200 (machinability good, 55/100), then C64210 (55/100).
Is aluminum bronze heat-treatable?
Some grades are. Check the conditions listed on each grade page.
C630 or C954 for a bushing?
C63000 is wrought bar with 345–415 MPa yield and finer grain; use it for shafts, small and medium bushings and anything highly loaded or shock-loaded. C95400 is the cast equivalent at about 240 MPa yield as cast (310 MPa quench-hardened), poured to near-net shape, so it wins on large diameters, flanged sleeves and short runs where bar would be mostly chips. C95500 splits the difference with nickel for strength and seawater.
C630 or C642 — which aluminum bronze machines better?
C64200. Its 2 % silicon and lower aluminum cut the machinability rating to about 60 against 30 for C63000, and it still yields around 240–310 MPa with good seawater resistance. Use C64200 for valve stems, nuts, gears and volume turned parts; keep C63000 for the shafts and bushings where its extra 100 MPa and galling resistance pay for the slower cut.