How to prevent corrosion in cable connections

When electrical conductors are connected in terminal blocks or screw clamps, the choice of materials is critical for long service life and safety.

The wrong combination can lead to corrosion, increased contact resistance, and in the worst case overheating.

Here is what you need to know.

Materials in our terminal blocks

The terminal block we use in OTAC-SW22T is built with:

• Screws: Steel, zinc-plated

• Spring: Phosphor bronze, nickel-plated

• Conductor clamp: Brass, nickel-plated

• Plastic: PBT, flame-retardant UL94V-0

Nickel-plated brass is a stable combination with copper conductors.

The zinc-plated screws are less critical, as they are not in direct electrical contact with the conductor.

Suitable cable materials

• Copper: Standard and fully compatible.

• Tinned copper: Even better, resists oxidation and works well in humid environments.

• Aluminum: Not recommended. High risk of galvanic corrosion and loose connections.

Avoid manually tinned wires

It may seem practical to tin stranded wires with solder, but this is a poor solution.

Solder is soft and creeps under pressure, which causes screw joints to loosen over time.

This practice is also forbidden by common standards (IEC/EN, UL).

Use ferrules

For stranded conductors, ferrules are the best option.

• They compress all strands into a uniform, solid surface.

• They are usually made of tinned copper, which ensures a stable, corrosion-resistant interface with the nickel-plated clamp.

• They provide even clamping and reduce the risk of loose connections.

Conclusion

For safe and long-lasting installations:

• Use copper or tinned copper conductors.

• Always use ferrules for stranded wires.

• Avoid aluminum conductors and solder-tinned wire ends.

Correct material choices and methods reduce the risk of corrosion and provide stable connections over time.