ZDDP content in mineral and synthetic motor base oils and its effect on electrostatic and tribological phenomena in a rotating shaft–oil–lip seal system

The paper presents the results of experiments on electrostatic and tribological aspects of different ZDDP (zinc dialkyldithiophosphate) contents when ZDDP is added to different mineral and synthetic motor base oils. Experiments were carried out in a rotating shaft–oil–lip seal system which is an experimental facility in whose interior a metal shaft rotated at given angular velocities, and where the level of tribocharging in the interfacial system was measured. The braking torque of a shaft was also measured. The braking torque generally decreased when an external DC electric field was applied to the system.