The internal cathodic protection of water tanks and boilers is the most economical anti-corrosion measure if it is paid great attention in the design stage. However, internal cathodic protection can also be used as a repair measure in the later stage of tank use to stop the development of corrosion.

Water tanks are used to store hot or cold drinking water, production water, cooling water, condensate or waste water. Filter tanks are used to filter and purify water, and reaction tanks are used for physical and chemical reactions (such as the removal of ozone). These tanks may be open, the water level may be variable, or they may be pressure vessels for filling water, such as heating or cooling surfaces, separation partitions, probes, connections, or distribution lines.