Contact corrosion
Engine wear - Complex shapes

Fretting wear", "fretting corrosion" or "false Brinelling", also known as "wear by small deflections" or "false Brinell effect" by bearing specialists, is the deterioration that affects surfaces in contact, loaded and subjected to very low amplitude movements (vibrations, micro-slides, small deflections) ranging from a few µm to distances of the order of a mm.

These surfaces are subjected to adhesive micro-contacts which, when sheared, give rise to adhesive transfer followed by the detachment of wear particles. But while the adhesive wear particles are evacuated from the contact by the high amplitude relative movement of the two surfaces, the wear debris generated by fretting corrosion remains in place, accumulates and oxidizes....