Galvanic corrosion (also called bimetallic corrosion) is a deteriorative electrochemical process that occurs when two dissimilar metals are in contact with each other in the presence of an electrolyte. This type of corrosion is characterized by the accelerated corrosion of one metal, while the other remains mostly unaffected. In other words, one metal becomes the anode and corrodes preferentially, thus sacrificing itself while protecting the other metal, the cathode.
Galvanic corrosion is relatively aggressive and causes millions of dollars in damage annually. Countermeasures to prevent its formation must be taken into consideration at the conceptual or early stages of the design process. (Discussed in more detail in Corrosion Control Considerations in the Equipment Design Process.) The causes of galvanic corrosion vary widely and can consist of several different types of chemical reactions. It is therefore essential to have a sound understanding of the underlying mechanisms and the factors that affect the development of this type of corrosion.