A review of the effect of biodiesel on the corrosion behavior of metals/alloys in diesel engines

ABSTRACT

Biodiesel is the most promising bio-based alternative to the large quantity of fossil diesel fuel used in the transportation sectors. However, its corrosive behavior when in contact with the diesel engine and fuel system components is of serious concern. The present work comprehensively reviews the impacts of biodiesel on the corrosion behavior of metal-based parts in diesel engines such as copper and copper-based alloys, aluminum and aluminum-based alloys, cast iron, carbon steel, and stainless steel. The corrosion mechanisms of the mentioned metals in biodiesel are also presented and discussed in detail. Methods applied to study the corrosion phenomenon and its level are also presented. The reasons leading to the higher corrosiveness of biodiesel vs. diesel fuel, including its higher hygroscopicity, higher electrical conductivity, higher polarity, higher solvency, the presence of water and oxygen in biodiesel promoting microbial growth, and finally, its auto-oxidation resulting in the generation of corrosive agents, i.e., monocarboxylic acids, are also detailed. Finally, the use of corrosion inhibitors in biodiesel to enhance metals/alloys resistance to corrosion is reviewed. Future research needs to further expand biodiesel utilization worldwide are also envisioned.

Graphical Abstract

KEYWORDS:

• Biodiesel
• corrosiveness
• diesel engine metals/alloys
• corrosion mechanism
• static immersion test
• corrosion inhibitor