Electric energy consists of the flow of electrons through a conducting medium between a positive pole and a negative pole.

The positive pole is referred to as an anode; the negative pole as a cathode. A common dry cell battery, such as a battery used in a flashlight, has a positive and negative pole.

For petroleum marketers, the concept of anodes and cathodes takes on significance as it relates to the corrosion of buried steel storage tanks and piping. Sacrificial anodes, buried in the soil adjacent to an underground tank, control the flow of electrical currents around the tank, and protect the tank from corrosion.

See also Cathodic protection.