Corrosion and Cathodic Protection in Underground Piping Systems

THE GALVANIC CELL The major corrosion concern in the water works industry is “galvanic” corrosion. Galvanic corrosion takes place due to current flow in a “galvanic cell” which is defined as (1) two dissimilar metals, an anode and a cathode, (2) in electrical contact with each other and (3) a common electrolyte. A galvanic cell is produced when the pipeline components come in contact with the soil. In such a cell, one of the metals, the anode, corrodes away and the other metal, the cathode, is protected. The rate of the corrosion is dependent on the current and the current density, which are functions of galvanic potential difference.