Copper, Brass, or Aluminum?
When engineers specify machined electrical parts, conductor material is often chosen late in the design cycle—or simply inherited from the last project. That can work for low-risk components, but for high-reliability electrical parts such as busbars, terminals, connector bodies, sensor housings, and power distribution components, the material choice directly affects electrical loss, temperature rise, long-term joint stability, manufacturability, and total cost.
For OEMs and product teams sourcing precision metal parts, the real question is not whether copper, brass, or aluminum is “best” in general. The better question is: which material best matches the electrical, mechanical, and manufacturing demands of this specific part?
At Aevion Metal Labs, that is usually where the best results start: not with a raw material preference, but with a combined review of conductivity, geometry, joint design, machining route, and finishing.
1.2 Thermal conductivity
Heat removal matters just as much as current carrying in many compact power parts. Typical C11000 copper shows thermal conductivity around 388 W/m·K, C36000 brass around 115 W/m·K, and 6061-T6 aluminum around 167 W/m·K.[2][4][6]
1.3 Strength and stiffness
Pure copper conducts extremely well, but it is mechanically softer than many brasses and structural aluminum alloys. By contrast, free-cutting brass and 6061-T6 offer much higher strength, which can be valuable for threads, clamped surfaces, and structural-current-carrying parts.[2][4][6]
1.4 Machinability
Machinability is often underappreciated during design. C11000 copper is only about 20% machinable relative to C36000 free-cutting brass, while C36000 is the benchmark at 100% machinability. 6061-T6 aluminum is also widely used because it balances good machining behavior with structural capability.[2][4][6]
1.5 Surface condition and joint reliability
For electrical interfaces, the joint is often the real reliability bottleneck. Aluminum requires specific attention because oxide must be removed or disrupted during assembly, and oxide-inhibiting compounds are commonly recommended. Connector design must also control creep loss and clamping-force relaxation over time.[7] For connector systems, plating choices such as tin, nickel, gold, and in some designs silver are used to match corrosion and conductivity requirements to the environment.[8]
For high-reliability electrical parts, the selection usually comes down to five property groups:
1.1 Electrical conductivity and resistivity
Electrical conductivity determines how efficiently a material carries current. Copper remains the benchmark at roughly 100–101% IACS for common high-conductivity grades such as C11000.[1][2] Brass drops well below that, while aluminum varies significantly by alloy—EC-grade 1350 aluminum is around 61–61.8% IACS, whereas 6061-T6 is closer to about 40–43% IACS.[4][5][6][7]
Copper remains the reference material for conductor performance. Common electrical copper grades such as C11000 are listed at roughly 100–101% IACS, with density around 8.9 g/cm³ and thermal conductivity near 388 W/m·K.[1][2]
That combination makes copper difficult to beat when a design needs:
In practical terms, copper is still the default choice for:
Copper’s downside is not electrical—it is manufacturing and cost related. C11000 is comparatively “sticky” to machine and far less forgiving than brass, with machinability around 20% relative to free-cutting brass.[2] That does not make copper a poor machining material; it means the shop has to control tool geometry, burrs, chip behavior, and edge quality more carefully.
For high-current parts, that trade-off is usually worth it.
Brass is often the best answer when the part must do more than carry current.
Free-cutting brass such as C36000 is typically around 26% IACS, with density around 8.49–8.50 g/cm³, and it sets the 100% machinability benchmark used to compare many other copper alloys.[3][4] Copper Development Association guidance also notes that lower-zinc brasses used in connector applications can reach higher conductivity, with some grades going up to about 56% IACS.[3]
That means brass gives up conductivity—but gains major advantages in:
This is why brass remains common for:
The key is path length. For a short current path, brass can be entirely acceptable if the section is sized properly. But for longer or higher-current paths, the conductivity penalty becomes expensive in heat and voltage drop. A C36000 brass path at about 26% IACS needs roughly 3.8× the copper cross-section to achieve similar resistance.[1][4]
So brass is rarely the right answer for long, heavily loaded busbars—but it is often the right answer for precision-machined electrical hardware where manufacturing quality and mechanical integrity matter just as much as conductivity.
A common mistake in online comparisons is treating “aluminum” as a single electrical material. In practice, that oversimplifies the decision.
4.1 Electrical-grade aluminum vs structural aluminum
Electrical-grade 1350 aluminum is listed around 61.0–61.8% IACS.[5] That is why aluminum remains attractive in conductors where weight and raw material economics matter.
But 6061-T6, which is frequently chosen for machined parts, is a different case. It is much stronger and easy to machine, but electrically it is only about 40–43% IACS.[6][7]
That distinction matters:
If the part is primarily a conductor, grades like 1350 or 6101 are closer to the right electrical family.[5]
If the part is a machined structural component that also carries current, 6061-T6 may be a better overall compromise.[6][7]
4.2 Weight advantage
6061-T6 aluminum has a density of about 2.7 g/cm³, versus roughly 8.9 g/cm³ for copper.[1][6] That is the main reason aluminum becomes attractive in:
transportation systems,
large enclosures,
battery structures,
rail and EV components,
and large-format power distribution assemblies.
Even though aluminum needs more section for the same resistance, its low density often makes it the better system-level choice.
For example, based on conductivity alone, EC-grade aluminum needs roughly 1.6× the cross-section of copper to achieve similar resistance.[1][5]
4.3 Joint design is the real challenge
Aluminum’s biggest reliability concerns are not surprising anymore—they are well known:
Oxide film
Aluminum oxide is electrically resistive, so connection prep matters. ILSCO installation guidance recommends cleaning aluminum conductor surfaces and applying oxide inhibitor before installation.[7]
Creep and relaxation under clamping
Aluminum connector systems must be designed so joint force remains stable over time; otherwise resistance and heating can increase.[7]
This does not make aluminum unreliable. It means aluminum must be used with correct joint design, correct hardware, correct prep, and correct process control.
A more accurate comparison for machined electrical parts is to separate electrical-grade aluminum from structural 6061-T6:
| Material / Typical Grade | Electrical Conductivity | Density | Thermal Conductivity | Machinability | Best Fit |
|---|---|---|---|---|---|
| Copper C11000 | ~100–101% IACS | ~8.9 g/cm³ | ~388 W/m·K | ~20% vs C36000 | Compact busbars, low-loss terminals, high-current links |
| Brass C36000 | ~26% IACS | ~8.5 g/cm³ | ~115 W/m·K | 100% benchmark | Machined terminals, threaded hardware, connector parts |
| Aluminum 1350 | ~61.0–61.8% IACS | ~2.7 g/cm³ | High for pure/EC Al family | Application-dependent | Lightweight conductors, larger busbars, rails |
| Aluminum 6061-T6 | ~40–43% IACS | ~2.7 g/cm³ | ~167 W/m·K | Good | Structural current-carrying parts, housings, supports |
Indicative values based on typical grade data and connector references.[1][2][4][5][6][7]
6.1 Compact high-current busbars and power links
If the design is constrained by space, temperature rise, and efficiency, copper is still the most straightforward choice.[1][2]
Best default: Copper
6.2 Machined terminals, contact hardware, and connector bodies
If the current path is relatively short and the part needs fine threads, crisp edges, stable tolerances, and high-volume machining efficiency, brass is often the most practical choice.[3][4]
Best default: Brass
6.3 Structural parts that also carry current
When the part is both mechanical and electrical—for example, a mount, bracket, housing, or support that also conducts—6061-T6 can be the right compromise, provided the electrical penalty is understood.[6][7]
Best default: 6061-T6 aluminum or a hybrid design
6.4 Large, weight-sensitive conductor systems
Where weight, material cost, and conductor length matter more than compactness, EC-grade aluminum is often the right answer.[5][7]
Best default: 1350/6101-type aluminum conductor families
6.5 High-reliability mixed-function assemblies
In practice, many of the best designs are hybrid:
This is also where a manufacturing partner adds the most value—because the right answer is usually at the intersection of material selection, tolerance strategy, joint design, and finishing, not in a single-property chart.
Many field failures blamed on “the wrong metal” are actually caused by one of the following:
For that reason, material selection should not be isolated from manufacturing planning. A copper part with poor contact geometry can fail. A brass part can perform perfectly if the current path is short and stable. An aluminum part can be highly reliable if the joint is engineered correctly.
That is the real engineering value behind working with a shop that understands both electrical behavior and production behavior. At Aevion Metal Labs, that usually means discussing current path, clamping surfaces, burr control, finishing, and assembly conditions before the part is released—not after the first heat-rise issue appears in testing.
Q: Is brass conductive enough for electrical terminals?
A: Often, yes—especially when the conductive path is short. C36000 is only about 26% IACS, so it is not a busbar material, but it remains very useful for machined terminals, threaded parts, and connector hardware because its machinability and mechanical behavior are so strong.[3][4]
Q: Is aluminum always a cheaper substitute for copper?
A: Not automatically. Aluminum can reduce weight dramatically, and EC-grade aluminum carries current well for its cost, but the joint design is less forgiving. If oxide control, clamping, and interface design are poor, lifecycle reliability can suffer.[5][7]
Q: Why is 6061 not the same as “electrical aluminum”?
A: Because 6061-T6 is primarily a structural aluminum alloy. It is much stronger than EC-grade 1350, but it conducts significantly worse. That makes it useful for combined structural-electrical parts, not always for maximum-efficiency conductor paths.[5][6][7]
Q: Should contact surfaces be plated?
In many connector and terminal applications, yes. Common options include tin, nickel, gold, and in some systems silver, depending on required corrosion resistance, conductivity, and service environment.[8]
Copper, brass, and aluminum all have valid roles in high-reliability electrical products—but they solve different problems.
For teams evaluating a new part—or replacing an existing copper, brass, or aluminum design—the biggest gains usually come from asking the right question early:
What does this part need to do electrically, mechanically, and in production?
If that question is answered well, material choice becomes much clearer.
[1] Copper Development Association, “C11000 Alloy”
[2] MatWeb, “Electrolytic Tough Pitch (ETP) Copper, UNS C11000”
[3] Copper Development Association, “Conductivity of Brass”
[4] MatWeb, “Free-Cutting Brass, UNS C36000”
[5] The Aluminum Association, “Table 16.3 Property Limits / Table 16.4 Equivalent Resistivity Values for Electric Conductors”
[6] ASM MatWeb, “Aluminum 6061-T6; 6061-T651”
[7] ILSCO, “Engineering Handbook for Electrical Connectors”
[8] TE Connectivity, “DEUTSCH Connector Stamped & Solid Contacts – FAQ”
