Aluminum bronze covers several cast and wrought copper alloys that keep their strength under high bearing loads, elevated temperature and seawater. Choosing between them is mostly a question of how much load, how corrosive the environment is, and how much the project can spend. This page lists the grades we machine bushings from, the numbers behind each one, and the cases where a tin bronze or manganese bronze would serve better.

What aluminum bronze actually is

Aluminum bronze alloys carry roughly 8–11% aluminum, usually with iron, nickel and manganese added. During solidification the aluminum forms a β (Al-Cu) phase and the iron forms hard κ (Fe₃Al) particles distributed through a softer α matrix. That two-phase structure is the reason these alloys behave differently from tin bronzes:

• Wear resistance comes from the hard iron-rich phases carrying part of the contact load, while the softer matrix accommodates misalignment.
• Corrosion resistance relies on a dense, self-healing alumina-rich surface film. In flowing seawater, aluminum bronzes generally show lower corrosion rates than 316L stainless steel, particularly where crevice conditions exist.
• Strength ranges from about 450 MPa up to 900 MPa depending on grade and heat treatment, roughly double the figure for a standard leaded tin bronze.
• Temperature capability extends well beyond what tin bronzes tolerate; continuous operation in the 250–300 °C range is normal, with short excursions higher.
• Biofouling resistance comes from copper ion release, which is why these alloys are common on seawater-cooled equipment.

The trade-offs are worth stating plainly. Aluminum bronze is harder and stronger than tin bronze, but it is less forgiving: it needs a hardened shaft, it tolerates less shaft deflection, and it embeds dirt poorly. Where the shaft is soft, the lubrication is borderline, or the housing is badly aligned, a leaded tin bronze such as C93200 is usually the safer choice; see the bushing material overview.

 

Grade comparison

The figures below are typical room-temperature values for cast material in the as-cast or lightly stress-relieved condition. Actual values depend on section thickness and casting method, so the numbers on the mill certificate govern.

Grade	Common equivalent	Nominal composition	Tensile strength	Hardness	Typical bushing use
C95200 / C95210	Basic cast aluminum bronze	Cu bal., Al 8.5–9.5%, Fe 2.5–4.0%	450–550 MPa	110–150 HB	Acid pump bushings, low-pressure valve guides, general bushings
C95400	CuAl11Fe4, highest-strength general grade	Cu bal., Al 10.0–11.5%, Fe 3.0–5.0%	585 MPa min	170 HB min	Heavy-load bearings, gear sleeves, earthmoving pins
C95500	Nickel aluminum bronze	Cu bal., Al 10.0–11.5%, Ni 3.0–5.5%, Fe 3.0–5.0%	760 MPa min (higher when heat treated)	190–240 HB	Hydraulic piston guides, rudder wear rings, high-load slow-speed bearings
C95800	CuAl10Fe5Ni5, cast nickel aluminum bronze	Cu bal., Al 8.5–9.5%, Ni 4.0–5.0%, Fe 3.5–4.5%, Mn 0.8–1.5%	620 MPa min	150–180 HB	Propeller hub bearings, seawater pump sleeves, condenser tube sheets
CuAl10Fe (EN CC331G / CW305G)	Aluminum iron bronze	Al 8.5–11%, Fe 2–4%, nickel-free	≥550 MPa	≥130 HB	Marine pump sleeves, coastal power plant liners, chemical valve seats
CuAl10Ni (EN CC333G / CW307G)	Aluminum nickel bronze	Al 8.5–11%, Ni 4–6%, Fe 4–6%	600–650 MPa	150–180 HB	Nuclear cooling pumps, offshore deck equipment, high-corrosion high-load service
SAE 68	Aluminum bronze to SAE specification	Composition varies by revision — verify against the current specification	Specified in the applicable revision	Specified in the applicable revision	Rolling mill and other thermally cycled slide bearings
AB1 / AB2 (BS 1400)	Superseded by BS EN 1982	AB1 ≈ CuAl10Fe3Mn2; AB2 ≈ CuAl10Fe5Ni5	Refer to BS EN 1982 values	Refer to BS EN 1982 values	Replacement parts on legacy UK and Commonwealth equipment

Grade names such as “952C” and “SAE 68” circulate widely in purchasing documents but are not backed by a single fixed composition. When they appear on a drawing, we ask for the standard revision before quoting.

Selecting a grade by operating condition

Condition	Grade commonly specified	Reason
Seawater or brackish cooling water	CuAl10Ni, C95800	Nickel addition improves corrosion-fatigue and cavitation resistance in chloride service
High load, slow oscillation, dirty environment	C95400, C95500	Higher hardness resists abrasive wear and brinelling
Non-oxidizing acids, process water with solids	C95200 / C95210	Good acid resistance at lower alloy cost
Elevated temperature with thermal cycling	SAE 68, CuAl10Fe	Retains strength and resists thermal fatigue cracking
Lead-free requirement (RoHS, potable water)	CuAl10Fe, C95200 lead-controlled heats	Aluminum bronzes are inherently low-lead when specified accordingly
Mixed metals in a seawater circuit	CuAl10Ni with insulated flanges	Noble position in the galvanic series requires attention to mating metals

Where two grades serve equally well, cost usually decides. As an indicative range, basic aluminum iron bronze costs noticeably less per kilogram than nickel-bearing grades, and the difference grows with nickel content. If the load is moderate and the medium is clean water rather than seawater, specifying CuAl10Ni buys performance the application will not use.

Casting method and machining

Most aluminum bronze bushings start as a casting. The route affects both the mechanical properties and the amount of material that has to be removed:

• Centrifugal casting gives a dense, fine-grained wall with impurities concentrated on the bore, which is then machined away. It suits bushings with a high length-to-diameter ratio and gives good properties in radial directions. See continuous and centrifugal casting.
• Continuous cast bar produces consistent stock for smaller bushings and lets us hold tighter concentricity with less stock removal.
• Sand casting handles very large or one-off geometries where tooling cost for centrifugal casting cannot be justified.

Near-net-shape casting then finishing on CNC turning centers typically removes 20–30% less material than machining from solid bar, which shortens lead time on larger diameters. Machining allowance of 2–3 mm per side on the OD and 3–4 mm on the bore is normal for bushings above 150 mm (6 in) diameter.

Limits worth knowing before specifying

Aluminum bronze is not a universal answer. These situations tend to point elsewhere:

• Unhardened shafts. Aluminum bronze is hard and has limited embeddability. On a soft or rough shaft it will score the shaft rather than polish it. We usually ask for a shaft hardness above 300 HB with a surface finish better than Ra 0.8 µm (32 µin).
• Misalignment and shaft deflection. The higher modulus means edge loading is transferred to the shaft rather than absorbed. Where alignment cannot be held, leaded tin bronze tolerates the condition better.
• Sulfur-bearing environments. Aluminum bronze performs poorly in sulfidic or strongly reducing acid conditions.
• Dezincification-prone media at high temperature. This affects brass rather than aluminum bronze, but mixed-alloy assemblies introduce it.
• Galvanic coupling to less noble metals in seawater without insulation or cathodic protection.

Fits, clearance and running-in

Clearance selection follows the same logic as other bronze bushings, with the added constraint that aluminum bronze has a lower coefficient of thermal expansion allowance than tin bronze:

• Start from the running clearance required by the application, typically 0.1–0.2% of shaft diameter, then add allowance for thermal growth of the shaft.
• Common fit practice is a fixed bushing in an H7 housing with a shaft finished to f7 or g6, adjusted for operating temperature.
• Measure the bore at 20 °C (68 °F) on the same equipment used for final inspection; see reading and measuring bearing tolerance.
• Graphite-plugged versions need a transfer film established in the first few hundred cycles; a short run-in at reduced load helps.

Where external lubrication is impractical, adding solid lubricant plugs turns these alloys into a maintenance-free bushing. Details on plug layout are covered in calculating plug size for graphite-plugged bearings.

Frequently asked questions

How does aluminum bronze compare with manganese bronze for bushings?

Manganese bronze such as C86300 reaches higher tensile strength and hardness, and suits very high loads at low speeds. Aluminum bronze offers better corrosion resistance, especially in seawater, and better high-temperature stability. Manganese bronze needs reliable lubrication; aluminum bronze tolerates marginal lubrication better when plugged with graphite.

Can aluminum bronze bushings run completely dry?

Yes, when they carry embedded solid lubricant plugs. A solid aluminum bronze bushing running dry without any lubricant film depends entirely on having very low PV values — light loads and slow speeds. Above roughly 1.0 MPa·m/min sustained, we recommend either plugged bushings or an oil-impregnated alternative.

Is C95500 always better than C95400?

Not automatically. C95500 has the nickel addition and higher strength, which matters under shock loading. Where the application is a plain rotary bushing in clean conditions, C95400 delivers comparable service at lower material cost. Nickel content should be justified by the environment or the load case.

Which standard governs the composition?

In North America ASTM B505/B505M covers continuous cast bar and B271/B271M covers centrifugal castings. European projects typically reference EN 1982 for ingots and castings with wrought designations in the CW series. A cross-reference of common designations is kept on our ASTM and DIN material pages.

What is the typical lead time for machined aluminum bronze bushings?

For centrifugal cast blanks in standard sizes, machining and inspection usually takes three to four weeks from drawing approval. Fully custom tooling adds one to two weeks. Small quantities machined from stock bar are faster.