Fretting corrosion occurs when there is a relative movement between a bearing ring and shaft or housing because the fit is too loose. The small wear particles oxidize and areas of rust appear on the outer surface of the outer ring or the bore of the inner ring. Corroded areas may act as fracture nodes leading to cracking of the ring.
Fretting wear is characterised by the small relative motion
amplitude in the order of microns - caused by vibrations or elastic
deformations are enough to penetrate the oxide layer, after which a
combination of adhesion and three body abrasion sets in. The small
wear particles oxidize quickly when exposed to the oxygen in the
atmosphere. On disassembly, a powder (debris) of oxidized abrasive
can be found, as a result of fretting corrosion.