Tribological behavior of the refined, bleached, and deodorized palm kernel as an alternative lubricant

The effects of zinc dialkyl dithiophosphate (ZDDP) concentration on tribological behavior of the Refined, Bleached, and Deodorized (RBD) palm kernel were analyzed using a pin-on-disk tribotester. RBD palm kernel was selected as a base lubricant due to its availability, low price, renewability, and being environmentally friendly. Commercial mineral oil (SAE 40) was used for comparison. The tests were performed at 2.5 m/s sliding speed under 9.8 N applied load for 60 minutes at 25°C temperature (±2°C). Worn surface of the pin was measured by the optical microscope to understand the wear mechanism involved. Compared with SAE 40, experimental results show that the addition of 5 wt% of ZDDP reduced the coefficient of friction to 21%. However, the anti-wear property was still lower, approximately at 23%. Besides, the tribological behavior of RBD palm kernel was improved with ZDDP additive concentration above 1 wt% where the best performance was at 5 wt%. At this concentration level, ZDDP additive was able to protect the surface against wear and oxidation and, at the same time, reduce coefficient of friction, wear rate, and surface roughness values