Corrosion of grey cast iron in biodiesel–diesel–ethanol (B20D70E10) blend: material degradation and fuel stability

This study presents a comprehensive investigation into the corrosion behavior of grey cast iron in a biodiesel–diesel–ethanol fuel blend (B20D70E10; 20% biodiesel, 70% diesel, 10% ethanol) and its associated fuel degradation. Immersion tests were conducted under two exposure conditions: prolonged ambient exposure at 25 °C for 962 h and accelerated exposure at 60 °C for 504 h. The novelty of this work lies in the integrated evaluation of grey cast iron corrosion and concurrent fuel degradation in a BDE blend under dual exposure conditions. At 25 °C, grey cast iron exposed to B20D70E10 exhibited a corrosion rate of 0.1924 mpy, higher than petroleum diesel (B0, 0.0726 mpy) but lower than pure biodiesel (B100, 0.8387 mpy). At 60 °C, the corrosion rate increased significantly to 0.6653 mpy, exceeding both B0 (0.1109 mpy) and B100 (0.2564 mpy), highlighting the dominant influence of temperature in ethanol-containing blends. Surface morphology revealed localized pitting and deposits, while FTIR confirmed chemical modification of the metal surface. Fuel characterization showed moderate changes in density, viscosity, and flash point, with most properties remaining within acceptable limits. Fuel degradation indices indicated lower oxidative degradation for B20D70E10 than B100, though greater than B0.