Material loss that happens when the oil film breaks down and asperities on two metal surfaces bond under heat and pressure, then shear apart, tearing metal from one side and plastering it on the other. Mild adhesive wear is part of running-in; severe adhesive wear becomes scuffing, galling or seizure. Similar metals, low viscosity, high sliding speed and heavy load all make it worse, and AW and EP additives fight it.
Metal is smeared from the cam lobe onto the follower, classic adhesive wear, the film wasn't holding.
Also heard as
- adhesion wear
Related terms
Scuffing
Sudden, severe adhesive damage where the oil film fails and sliding surfaces locally weld and tear.
Galling
Severe adhesive wear where sliding metals seize and tear, raising lumps of transferred metal.
Pickup
Metal transferred from one sliding surface onto another, seen as smeared lumps after adhesive wear.
Boundary lubrication
Regime where surfaces touch through the oil and protection comes from chemical surface films, not fluid pressure.
EP
Extreme pressure: additives or oils that react with metal under heavy load to prevent welding and scuffing.