Fretting corrosion

Fretting corrosion appears as a reddish-brown to black deposit on the fit surfaces between bearing ring and shaft or housing. Micro-movements in the fit continuously remove protective oxide layers; the fine debris oxidizes and acts abrasively. ISO 15243 classifies it under frictional corrosion. Consequences include loss of fit, creeping rings, local stress concentrations up to ring fracture, and difficult dismounting. The main cause is a fit too loose for the load case — especially circumferential load on a ring with a clearance fit — plus seat form errors. Remedies: correct fit selection, accurate seat geometry, mounting paste, and seat inspection before fitting a new bearing.