Antiwear: describes additives, most commonly ZDDP or ashless phosphorus compounds, that form a glassy phosphate film on metal under rubbing heat and moderate load. AW hydraulic oils are the default for gear and vane pumps, where boundary contact inside the pump never stops. AW chemistry acts at lower temperatures than EP chemistry and is gentler on yellow metals, though zinc types can hydrolyze when water gets in.
Standard AW 46 for every hydraulic power unit on the line, one oil and no mix-ups.
Also heard as
- antiwear
- AW hydraulic
Related terms
ZDDP
Zinc dialkyldithiophosphate, the classic antiwear and antioxidant additive in engine and hydraulic oils.
EP
Extreme pressure: additives or oils that react with metal under heavy load to prevent welding and scuffing.
Boundary lubrication
Regime where surfaces touch through the oil and protection comes from chemical surface films, not fluid pressure.
Additive package
Pre-blended mix of performance chemicals that a blender adds to base oil to make a finished lubricant.