Abstract: A corrosion protection system for steel or corrodible metal storage tanks and the like uses two external electrodes which develop a voltage potential used to protect against internal corrosion. One of the external electrodes is connected to an internal sacrificial electrode which is selected such that the rate of corrosion is small and the resulting contamination in the tank is acceptable. The preferred internal electrode is made of a ferro alloy and is connected to the external electrode which has a potential similar to graphite or at least of the same polarity relative to steel. The other electrode is a sacrificial electrode preferrably of zinc or magnesium.

Abstract: The anode comprises a core of a metal having a negative potential relative to steel, and an adjacent electrode of a material having a positive potential relative to steel. The adjacent electrode has a first substrate generally facing the core and a second substrate in direct electrical communication with the first substrate end of a material having a negative potential relative to steel substantially shielded from the core by the first substrate. The anode includes a suitable porous material between the core and the electode which tends to retain water. The anode produces a potential voltage in the presence of an electrolyte between the core and electrode which is the collective effect of the material of the core and the materials of the electrode. Such an anode can produce a higher potential voltage than conventional sacrificial anodes and be designed for particular desired voltage potentials.