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Preventing Galvanic Corrosion Between Fasteners and Metals
Understanding the galvanic scale. What happens when stainless steel screws are installed into aluminum, and how to use non-conductive nylon and EPDM isolation washers.
The Galvanic Series Explained
When two dissimilar metals touch in the presence of an electrolyte (such as rainwater, humidity, or sea salt air), an electrochemical battery is created. The more active metal (anode, e.g. Aluminum or Zinc) rapidly corrodes to protect the more noble metal (cathode, e.g. Stainless Steel or Copper).
Preventative Measures
- Dielectric Isolation Washers: Place nylon or EPDM washers between the bolt head/nut and the aluminum sheet to break electrical contact.
- Anodic Surface Area Ratio: Always ensure the fastener is more noble than the large surface plate, never the reverse.
- Anti-Seize & Barrier Pastes: Use zinc-rich or nickel-based anti-seize paste on threads.