Electrical fluting

Electrical fluting occurs when current passes through a rolling bearing. Discharges through the lubricant film create microscopic melt craters which, under continued overrolling, organize into a grey washboard-like pattern across the raceway. ISO 15243 lists electrical erosion as a separate damage class. Affected bearings produce tonal noise and increased vibration, and the discharges also degrade the grease. The most common cause is high-frequency bearing currents in inverter-driven motors; faulty earthing or welding current routed through the bearing has the same effect. Remedies include insulated coated bearings, hybrid bearings with ceramic rolling elements, shaft grounding rings and proper earthing practice.