The effect of biodiesel fuel made from Jatropha curcus L. seed oil and methanol on the corrosion rates of mild carbon steel (MCS) and aluminium (Al) was investigated and compared with those of the conventional petroleum diesel and its blend. Static immersion tests in diesel (B0), biodiesel-diesel blend (B50) and biodiesel (B100) fuels were carried out at room temperature for 18 weeks. Corrosion rates of MCS and Al in these fuels were determined at an interval of 3 weeks by the weight loss method. Also, during the period of investigation, the fuels were analysed by measuring the total acid number (TAN). It was observed from the results that the corrosion rates for these metals were higher in B100 compared to the corrosion rates in B50 and B0. The corrosion rates for MCS were found to be higher than corrosion rates for Al in these fuels. The corrosion rate for MCS at the end of our investigation were 0.026, 0.022 and 0.011 mpy in B100, B50 and B0 respectively, while that for aluminium were 0.016, 0.0099 and 0.0025 mpy in B100, B50 and B0 respectively. There was an increase in the TAN during the period of investigation. Maximum TAN of 3.53 mg KOH/g was observed in the B100 fuel in which MCS was immersed, while the lowest TAN of 0.69 mg KOH/g was measured in B0 containing aluminium.