What Does Electrolytic Corrosion Mean?
Electrolytic corrosion is a process of accelerated corrosion. In this process, a metallic surface is continuously corroded by other metal it is in contact with, due to an electrolyte and the flow of an electrical current between the two metals, caused from an external source of electromotive force (EMF).
This form of corrosion causes widespread damage to critical equipment, and ways and means of monitoring, controlling and preventing this corrosive damage have been developed and implemented.
Corrosionpedia Explains Electrolytic Corrosion
Electrolytic corrosion is often confused with galvanic corrosion. While galvanic corrosion is driven by the difference in corrosion potential between two metals, the electrolytic corrosion is driven by the external sources of EMF. In the case of large motor bearings and generator bearings, induced EMF of the shaft results in current flow in the bearing, resulting in bearing corrosion in the shape of pinhole-type pits formed on the bearing surface.
Similarly, in the case of electrolytic corrosion of pipes, high-voltage direct current equipment and marine equipment, some external leakage current is always the driving force for the corrosion.
Prevention of this form of corrosion involves devices that break the continuity of the circuit or providing an alternate low-resistance path to connect the leakage current directly to the ground. For example, in the case of motor or generator bearings, a current collector mechanism with a brush holder and a brush makes contact with the rotating shaft, connecting the shaft to ground. Alternatively, the bearing pedestals may be insulated from ground to break the path of leakage current.