A critical review on the tribological compatibility of automotive materials in palm biodiesel

• Biodiesel is creating tribology related new challenges world over.
• Tribo-corrosion in biodiesel is yet to be studied in details.
• Possible influencing factors for wear, corrosion and tribo-corrosion have been enlisted.
• Auto-oxidation, moisture absorption, compositional instability, etc. are the major concerns.

Although the compatibility of biodiesel with the key components of automobile engine such as cylinder, pistons, piston rings, connecting rods, bearings, etc. have posed a big challenge to tribologists, they have yet to come up with a solution to reduce tribological degradation of different metals as well as the used fuel. Some efforts have already been given to understand the corrosion and wear of automotive materials in diesel and biodiesel. It was found that though biodiesel is more corrosive than diesel, it provides better lubricity in terms of wear and friction. This finding has led us to the conclusion that the combined effect of wear and corrosion on materials and the consequent effect on biodiesel degradation could be crucial and yet to be investigated. The present study also highlighted some other relevant factors which showed notable implications on wear and corrosion in biodiesel. Those factors including auto-oxidation, moisture absorption, change in fuel properties (e.g. TAN number, viscosity, density, etc.) are found to have important influence for understanding the science behind tribology in biodiesel.