Non- edible oils from the plant seeds are the most promising alternative fuel for diesel engines as they are renewable, environment friendly, non-toxic, biodegradable, no sulphur and aromatics, favourable heating value and higher cetane number. But their inherently high viscosity compared to fossil diesel is undesirable for diesel engines. Lowering the viscosity can be achieved by breaking the triglyceride molecules and separating the fatty acid molecules from the glycerine molecules - transesterification. Biodiesel is more susceptible to oxidative attack than diesel fuel. The rate of oxidation is determined by the degree of unsaturation in the fatty acid alkyl ester chain, water content and environmental factors such as temperature, nature of storage container and air exposure during storage. Acceptable storage tank materials include mild steel, stainless steel, fluorinated polyethylene and polypropylene. Biodiesel has a solvent effect which releases the deposits accumulated on tank walls leading to corrosion. In the present investigation, the compatibility of biodiesel from Pongamia pinnata (PBD) and Jatropha curcus (JBD) and their different blends with commercial diesel (5%, 10% and 20%) with mild steel has been studied by mass loss method for a period of 100 h. 3% NaCl was used to depict water contamination. Though negligible corrosion rates were observed in both the biodiesels, corrosion rate in JBD was found to be higher. The surface topography of the metal samples after the exposure period was analyzed by scanning electron microscopy. The surface profile, pit distribution and pit density of the metal coupons were determined by laser profilometry. The wettability studies also supported the non corrosive nature of the biodiesel used.
Biodiesel, Pongamia pinnata, Jatropha curcus, Corrosion, Wettability