Short answer
Galvanic corrosion is a corrosion mechanism that can occur between dissimilar metals in electrical contact in a suitable electrolyte. Knowing only the names of the two metals is not enough to decide definitively whether an assembly is safe or unsafe.
Source: S098
Technical explanation
The Swagelok materials guide explains the contact of materials with different electrode potentials in the presence of an electrolyte as the basis of this mechanism. Moisture or liquid, the contact condition and the actual material pairs are evaluated. Supports, clamps and connection parts are also part of the system; the examination is not limited to internal surfaces in contact with the fluid. A general potential table should not be turned into a product suitability engine without considering surface condition and environment.
Source: S098
Topic-specific checkpoints
| Item | Description |
|---|---|
| Material pair | Actual alloys and surfaces |
| Contact | Electrical connection path |
| Electrolyte | Moisture, salt water or process fluid |
| Remedy | Evaluated together with mechanical and electrical functions |
Source: S098
How to evaluate it in practice
For a corrosion investigation, mark on the drawing all metal parts in the assembly and the areas where moisture can accumulate. If the problem is concentrated at a specific contact point, separate it from general rusting records. A proposal for insulation or a material change should go to an engineering assessment together with the requirements for mechanical retention and, where necessary, electrical continuity. Do not compromise another safety function by adding random plastic spacers. In the post-correction monitoring plan, observe the same contact area. Do not close out the galvanic corrosion risk without evaluating the metal pair, the electrolyte and the electrical contact path.
Original editorial recommendation; not a clause of a standard.
Frequently asked questions
Does galvanic corrosion always occur when two dissimilar metals are placed side by side?
The conditions are evaluated together. Necessary environmental elements such as electrical contact and electrolyte must not be overlooked.
Source: S098
Source coverage
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S098
Materials of Construction Swagelok · accessed 2026-10-19 Descriptions of corrosion mechanisms and material selection; quantitative limit tables not imported