Effect of copper and mild steel on the stability of palm biodiesel properties: A comparative study

The scarcity of fossil fuel has recently been introduced as a major concern to energy policy. This crisis has prompted the search for alternative energy sources. Biodiesel can be considered as one of the potential candidates of energy sources in order to resolve this problem. Most of the fuel properties of biodiesel are very close to that of petroleum diesel. However, commercial use of biodiesel in the automobile engine is being limited because of its unstable fuel properties. Instability of the fuel properties appears to be more aggravated when biodiesel comes in metal contact. The present study is intended to investigate the stability of different fuel properties and chemical composition of palm biodiesel upon exposure to copper and mild steel. Static immersion tests were performed by exposing metallic coupons in palm biodiesel at room temperature for different periods viz., 20, 40, 60 days. Compositional analysis of biodiesel was conducted by gas chromatography. Investigated fuel properties include induction period, total acid value, water content, calorific value, viscosity, density, cloud point, pour point, etc. Effect of biodiesel on metal surfaces was examined by measuring the corrosion rate and conducting SEM/EDS analysis. It is found that copper has strong influence in changing fuel properties especially for viscosity, water content, calorific value, density, etc. Compositional analysis of biodiesel showed that principal unsaturated constituent of palm biodiesel, methyl oleate reduced more in copper exposed biodiesel than that in mild steel exposed biodiesel. Formation of poly unsaturated methyl linoleate was observed in both metal exposed palm biodiesel.