CUPAL vs Pure Copper vs Aluminium — A Comparison

Q: Which is the better choice, CUPAL or pure copper?

It depends on the joint you are making. For pure copper-to-copper joints, pure copper is ideal because it has the highest conductivity. Where copper has to be joined to aluminium, however, CUPAL is the better choice: it eliminates galvanic corrosion and weighs nearly half as much as copper.

Q: How much lighter is CUPAL than pure copper?

CUPAL has a density of 4.60 g/cm³ compared with 8.96 g/cm³ for pure copper, making it roughly 49% lighter. This is a significant advantage in switchgear, electric vehicles and overhead-line applications where dead load matters.

Q: Why does CUPAL need a larger cross-section?

CUPAL's conductivity is 41.9 m/(Ohm·mm²), about 72% of pure copper, so roughly a 1.41× cross-section is needed for equivalent conduction. In high-frequency applications, however, only the surface layer matters because of the skin effect, so CUPAL's copper side is just as effective as pure copper.

Q: Is CUPAL more expensive than aluminium?

On a per-kilogram basis, CUPAL's price sits in the middle band: typically cheaper than pure copper but more expensive than aluminium. The exact figure is always determined by current copper and aluminium exchange prices and the prevailing currency rate.

Q: Does CUPAL eliminate galvanic corrosion between copper and aluminium?

Yes. CUPAL is the only material that offers a copper side and an aluminium side at once, so the same metal contacts each face. The critical Cu/Al transition sits inside the composite, protected from moisture, which means galvanic corrosion is completely eliminated.

When you need a solution for joining copper and aluminium conductors, three main options are available: pure copper, aluminium, or the CUPAL bimetal composite material. This article compares these materials in detail.

Comprehensive comparison table

Property	Pure copper	CUPAL (70/30)	Aluminium
Density	8.96 g/cm³	4.60 g/cm³	2.70 g/cm³
Conductivity	~58 m/(Ohm·mm²)	41.9 m/(Ohm·mm²)	~36 m/(Ohm·mm²)
Relative conductivity (vs Cu)	1.00	0.72	0.62
Required cross-section (vs Cu)	1.00x	1.41x	1.61x
Thermal conductivity	401 W/(m·K)	265 W/(m·K)	237 W/(m·K)
Weight (vs Cu)	100%	~51%	~30%
Typical price (per kg)	Highest	Intermediate (Al < CUPAL < Cu)	Lowest
Galvanic corrosion at Cu–Al joint	Present	Solved	Present
Solderable	Yes	Yes (copper side)	Limited
Electroplatable	Yes	Yes (copper side)	Limited

Detailed analysis

Weight

CUPAL is 49% lighter than pure copper. This delivers significant advantages:

In switchgear: Lower load on mechanical components, more favourable for accelerated masses (e.g. circuit breakers)
In electric vehicles: Every gram counts; CUPAL busbars are half the mass of their copper alternatives
In overhead-line applications: Lower dead load
During installation: Easier handling, less labour

Electrical conductivity

CUPAL's conductivity is 41.9 m/(Ohm·mm²), which is 72% of pure copper. This means that a 1.41× larger cross-section is required to achieve equivalent conductivity.

It is important, however, to take the following into account:

In high-frequency applications, only the surface layer matters because of the skin effect — CUPAL's copper side is just as effective as pure copper
The contact resistance of a CUPAL-based Cu/Al joint is low and stable, because the critical transition zone is protected from moisture inside the composite
In practice, the 1.41× increase in cross-section is acceptable in many applications, especially in light of the nearly halved weight

Cost

On a per-kilogram basis, CUPAL's price sits in the middle of the three materials — typically cheaper than pure copper and more expensive than aluminium. The exact figure is always determined by current copper and aluminium exchange prices and the currency rate, so a specific number is given by the quotation at the time.

Further cost considerations:

Raw material: the 70% aluminium content can be cheaper per kilogram than pure copper at the equivalent cross-section
Processing: CUPAL can be worked just like pure copper — it adds no extra processing cost
Service life: the protected Cu/Al transition can reduce maintenance and repair costs compared with a direct Cu/Al joint
Safety: preventing galvanic corrosion reduces the risk of failure

Corrosion protection

This is CUPAL's most important advantage:

Joint type	Risk of galvanic corrosion
Copper + Copper	None
Aluminium + Aluminium	None
Copper + Aluminium (direct)	HIGH
Copper + CUPAL + Aluminium	NONE

CUPAL is the only material that provides a copper side and an aluminium side at the same time, thereby completely eliminating galvanic corrosion at the junction of the two metals.

When to use CUPAL?

CUPAL is the ideal choice if:

You need to join copper and aluminium conductors
Galvanic corrosion has to be prevented
Weight reduction is required (vs. pure copper)
You need a long-life, low-maintenance Cu/Al joint

Pure copper is the choice if:

Only copper-to-copper joints are being made
Maximum conductivity is the primary concern
Weight is not relevant
Price sensitivity is not an issue

Aluminium is the choice if:

Only aluminium-to-aluminium joints are being made
Minimum weight is the primary concern
Maximum cost savings are required

Summary

CUPAL is not a compromise solution — it is a material engineered specifically for the problem of copper-aluminium transition joints. Wherever dissimilar metals meet, CUPAL is the optimal choice: it combines the advantages of copper and aluminium while eliminating their main drawback, galvanic corrosion.

Want to learn more? Request a quote or visit the Knowledge Base!

Frequently asked questions