- AW additive
AW additives, or antiwear additives, are additives for
lubricantsto prevent metal-to-metal contact between parts of gears. EP additivesare usually used in applications such as gearboxes, while AW additives are used with lighter loads such as bushings.
AW additives typically contain
Some popular AW additives are:
zinc dialkyl dithio phosphate(ZDDP), probably the most widely used in formulated engine oils, also acts as a corrosion inhibitorand antioxidant
Tricresyl phosphate(TCP), used for high-temperature operation, often used as an AW and EP additive in turbine engine lubricants, and also in some crankcase oils and hydraulic fluids
Halocarbons ( chlorinated paraffins), for extreme pressure operations
Glycerol mono oleate
Stearic acid, adhering to surfaces via reversible adsorption process under 150 °C, which limits its use to mild contact conditions.
Some formulations use
colloidal PTFE ( Teflon), but its efficiency is controversial.
Many AW additives function as EP additives, for example
organophosphates or sulfurcompounds.The mechanism of function of TCP and ZDDP is explained in EP additives.
Under extreme pressure conditions, the performance of AW additives becomes insufficient and designated
EP additives are required.
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