Bi-Metallic Corrosion: A Hidden Danger in Fastener Assemblies

Keywords: Galvanic corrosion, dissimilar metals, fastener compatibility

When two different metals (like steel and aluminum) are electrically connected in the presence of an electrolyte (e.g., saltwater), one metal (the less noble, like steel) corrodes faster. This is galvanic or bi-metallic corrosion. Using a steel bolt with an aluminum part without isolation can rapidly eat away at the aluminum. The solution is to use fasteners made of a metal compatible with the base material or to use insulating washers and sleeves to break the electrical path.