A puzzle to corrosion engineers was the onset of galvanic leaks in soil pipes after street trolleys discontinued service. It was discovered that there had been a flow of current to the pipes which created "negative areas," and this in turn prevented the development of corrosion. For a long time it was known that pipes near the trolley substation had to have stray currents removed in order to neutralize "positive or anodic areas." If this was not done, galvanic breaks occurred. At the anodic area the current leaves the pipe, causing iron ions to enter the soil water which quickly forms hydrogen ions that move to the cathode areas, leaving behind rusty tubercles of iron.1
Galvanic breaks in gas transmission systems are prevented by making the pipe a cathodic area. Anodes of magnesium or other suitable metals are spaced along the pipe lines. They are connected by insulated cables
GAUL LE. Epoxy Dermatitis from Installing Cathodic Protection. Arch Dermatol. 1962;86(1):77. doi:10.1001/archderm.1962.01590070083015
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