Galvanic action is a reaction caused when two electrochemically different metals are exposed to an electrolyte and electrically conducted, causing a transfer of electrons and ions from one metal to the other. Galvanic action is more commonly known as galvanic corrosion.
The metal that transfers the ions and electrons to the other is known as an anode. The loss of these ions and electrons causes the anode to corrode more quickly than the other metal, which is called the cathode. Cathodes are typically more stable than anodes and corrode at a less rapid rate than anodes. Special coatings must be applied to metals susceptible to galvanic action to avoid corrosion.