Extreme pressure agents react with metal surfaces during operation at elevated temperatures, creating a protective coating that can withstand extreme heat and pressure.  The coating protects two mating metal surfaces from scoring and seizing.  Antiwear agents perform in a similar manner, but tend to operate under lower loads and pressures.

Extreme pressure agents are used in gear oils, other power-transmitting fluids, load bearing greases, and metalworking fluids.  They are usually supplemented with antiwear additives to make them effective across a wide range of conditions.

Many effective extreme pressure agents and antiwear additives are corrosive to metals, so they’re typically formulated to balance protection with corrosivity.

Antiseize additives are a separate class of antiwear additives that perform independently of temperature. They improve boundary lubrication by forming a protective film through deposition, and are generally used in greases, some industrial oils, and various break-in lubricants.