Fretting corrosion
Tiny movements between ring and seat grind off rust-coloured powder. Urgency
Chemical attack from water, or micro-movement that keeps stripping the protective oxide.
What fretting corrosion looks like
- Reddish-brown powder or stains on the bore or outside surface of a ring
- Worn, polished or pitted patches that match the shape of the shaft or housing seat
- Sometimes the seat itself is damaged and the ring no longer sits firmly
Rotec AI schematic illustration. It shows the typical pattern and is not a photograph of a real bearing.
How fretting corrosion develops
If a ring is not held firmly on its seat, load and vibration make it shift by microns each turn. The thin protective oxide layer is scraped away over and over, exposing fresh steel that rusts into red powder. It leaves the fit looser and the support uneven, which can lead to creep, fatigue cracks and fracture.
How fast it progresses: Progressive: a loose fit gets looser. Left alone it can end in ring creep or a cracked ring.
Causes of fretting corrosion
Design & seats
- Fit too loose for the load, or a seat that is rough, oval or out of tolerance
Mounting, handling & storage
- Seat damaged during an earlier overhaul, uneven support, dirt under the ring
Operating conditions
- Vibration, heavy load or load reversal that makes the ring move
How to confirm it is fretting corrosion
- Measure seat diameter and roundness against the specification, even after machine overhauls
- Check for wear marks on both ring and seat
- Uneven shiny and dull patches mean the ring was not supported evenly
How to fix and prevent fretting corrosion
- Choose the fit for the real load and which ring rotates
- Machine seats to the right size and form, and check them after any repair
- If a loose fit must be tolerated, consider an anti-fretting paste or a coated seat or sleeve
- Correct uneven support before fitting the new bearing
Easily confused with
- Moisture corrosion: Moisture corrosion is on the raceways; fretting corrosion is on the fitted surfaces.
- Abrasive wear: Creep can polish a seat like abrasive wear, but fretting leaves the red powder.
Other corrosion modes
Questions about fretting corrosion
What causes fretting corrosion in a bearing?
Fit too loose for the load, or a seat that is rough, oval or out of tolerance. Seat damaged during an earlier overhaul, uneven support, dirt under the ring. Vibration, heavy load or load reversal that makes the ring move.
How do you fix or prevent fretting corrosion?
Choose the fit for the real load and which ring rotates. Machine seats to the right size and form, and check them after any repair. If a loose fit must be tolerated, consider an anti-fretting paste or a coated seat or sleeve.
What does fretting corrosion look like?
Reddish-brown powder or stains on the bore or outside surface of a ring. Worn, polished or pitted patches that match the shape of the shaft or housing seat.