Galvanic Corrosion in Solar Structures: Electrochemical Isolation of Dissimilar Metals
Understanding the electrochemical galvanic series, electrolyte bridging, and effective isolation techniques to ensure 30-year corrosion immunity.
Key Engineering Takeaways
- ✓ Direct stainless steel A2/A4 fasteners in anodized aluminum are safe per ISO 9223
- ✓ Never place bare carbon steel or copper grounding cables in direct contact with aluminum
- ✓ Always install high-density EPDM separator pads between aluminum rails and steel purlins
The Galvanic Electrochemical Cell in Outdoor Racking
When dissimilar metals with different electrode potentials touch in the presence of an electrolyte (rainwater, humidity, coastal salt mist), galvanic corrosion occurs. Aluminum (-1.66V) is anodic to stainless steel (+0.00V) and copper (+0.34V), causing accelerated sacrifice of aluminum if not properly isolated.
Area Ratio Principle & Stainless Fastener Safety
The rate of galvanic attack is determined by the cathode-to-anode surface area ratio. When small stainless steel A2 bolts (small cathode) are embedded in a large anodized aluminum rail (large anode), the corrosion current density on the aluminum is negligible, making direct stainless-to-aluminum threading safe in normal atmospheres.
Isolation from Carbon Steel Purlins
Direct contact between aluminum rails and ungalvanized or weathered structural steel purlins must be strictly prevented using vulcanized EPDM rubber pads or nylon isolation washers.
Frequently Asked Technical Questions
Why do you supply EPDM pads with your L-feet?
Can copper grounding wires touch aluminum rails?
Require Project Statics Calculation?
Our engineering desk calculates project-specific wind uplift and snow load moment capacities according to Eurocode 9 within 24 hours.