Alternating Current Corrosion (AC Corrosion)

Last updated: February 15, 2019

What Does Alternating Current Corrosion (AC Corrosion) Mean?

Alternating current corrosion is a type of corrosion that originates from AC sources like overhead alternating current power lines or buried pipelines. This can be brought about by a coating defect in soil with low resistivity.

Alternating current corrosion occurs when buried pipelines' coatings such as polyethylene are damaged, which exposes the steel pipes to soil.


Corrosionpedia Explains Alternating Current Corrosion (AC Corrosion)

Alternating currents that exit steel surfaces are considered to be a blend of capacitive and resistive current. The resistance is referred to as the polarization resistance, which is the transformation resistance that converts electron conductance into current conductance while the capacitance makes up the electrochemical layer of the steel surface.

The capacitive portion of the current does not lead to corrosion, but causes reduction and oxidation of various chemical species on the metal surface. The resistive part is the part that causes corrosion in the same manner as direct current corrosion.

The association between the resistive and capacitive current is a vital decisive factor for alternating current corrosion since massive resistance currents leads to immense corrosion. This kind of relationship is dependent on the soil/water composition near the surface of the steel.

To prevent AC corrosion, a cathodic protection system as well as the application of coatings is greatly beneficial.


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