Corrosion is Electric

The corrosion process (anodic reaction) of the metal dissolving as ions generates some electrons that are consumed by a secondary process (cathodic reaction). These two processes have to balance their charges. The sites hosting these two processes can be located close to each other on the metal's surface, or far apart depending on the circumstances. This simple observation has a major impact in many aspects of corrosion prevention and control, for designing new corrosion monitoring techniques to avoiding the most insidious or localized forms of corrosion.

One simple way to illustrate the two processes in a corrosion reaction is to use an external power source as illustrated in the corrosion current experiment.