Copper and Stainless Steel: How to Connect PE Earth the Right Way
Stainless steel (RVS/INOX) and copper may both seem like durable, corrosion-resistant metals — but in practice, they are not good friends. When directly bonded in outdoor environments, galvanic corrosion sets in, and connections can fail prematurely. This is especially problematic when connecting your protective earth (PE) to stainless-steel hardware such as clamps, brackets, or antenna mounts.
Why Copper and Stainless Clash
When two dissimilar metals make contact in the presence of moisture, a galvanic cell is created. Copper is more noble than stainless steel, meaning the stainless becomes the sacrificial element. Over time, the joint oxidizes, resistance rises, and eventually the earth bond may fail. For safety and RF performance, that’s unacceptable.
In seawater or damp outdoor conditions, metals line up on a “galvanic series.” The further apart two metals are on this chart, the faster corrosion happens when they touch. Copper sits near the noble end, while stainless steels (304/316) are less noble. Bolt them together, add moisture, and the stainless sacrifices itself — slowly corroding away. That’s why plating or protective paste is essential when mixing them.
The Proper Way: Plated Crimp Eyelets
The recommended solution is to use a tin- or nickel-plated crimp eyelet on the copper earth conductor. The plating forms a barrier between copper and stainless, preventing direct galvanic action. A properly crimped and bolted connection gives you long-term stability and low resistance.
When Eyelets Are Not Possible
Sometimes, eyelets are impractical — for example, when bolting to flat stainless plates or when high surface conductivity is required. In those cases, use anti-corrosion joint compounds designed for mixed-metal contact:
- Würth CU 800 — a copper-based conductive paste that prevents oxidation while maintaining low contact resistance.
- Würth AL 1100 — an aluminum-based conductive grease, ideal when stainless and copper must be pressed together in outdoor installations.
Both products are available here: RF.Guru Antenna Maintenance Collection.
Installation Tips
- Always clean surfaces before assembly — remove oxides and dirt.
- Apply a thin, even layer of paste under the contact point.
- Tighten stainless hardware firmly, but avoid over-torquing (to prevent thread galling).
- For outdoor use, seal exposed joints with self-amalgamating tape or cold shrink for maximum lifetime.
Comparison at a Glance
| Method | Corrosion Risk | Contact Resistance | Longevity | Recommendation |
|---|---|---|---|---|
| Direct copper to stainless | High (galvanic cell) | Rises over time | Poor | Not recommended |
| Plated crimp eyelet | Low (barrier plating) | Stable | Excellent | Best practice |
| Conductive paste (CU 800 / AL 1100) | Very low (protected film) | Stable if maintained | Very good | Best alternative |
Mini-FAQ
- Why can’t I just bolt copper wire to stainless steel? — Because galvanic corrosion will degrade the bond and increase resistance over time.
- Is soldering an option? — No, stainless steel is not easily soldered, and solder joints are not mechanically robust outdoors.
- What’s the best long-term method? — A plated crimp eyelet plus conductive paste, sealed against moisture.
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