Evaluation of the corrosion inhibitory effect of the ecofriendily additive of Terminalia Catappa leaf extract added to soybean oil biodiesel in contact with zinc and carbon steel 1020

Natural antioxidants have been studied and is know to bring characteristics such as sustainability and environmental compatibility to the process. The tropical almond (Terminalia catappa) leaf extract was used as antioxidant additive to the soybean oil biodiesel in order to verify the improvement of its corrosive property in contact with zinc and carbon steel 1020. Gravimetric test according to ASTM G1-03 and G31 standards was used at room temperature for 2520 h and 60 degrees C for 1440 h. The morphology of the metal plates was analyzed by Scanning Electron Microscopy/Dispersive Energy Spectroscopy, X-ray Diffraction and the biodiesel through acidity index, Fourier Transformed Infrared Absorption Spectroscopy. At the end of the tests the carbon steel 1020 suffered no corrosion. However, for zinc mild corrosion was observed at room temperature and accentuated at 60 degrees C (efficiency of inhibition of 78.41% and 8.15%, respectively; increase activation energy in 31%). Interesting result is that at room temperature a greenish protective layer was observed in the region exposed to fuel from antioxidant components present in the plant for both metals. The results of this work indicate that the plant extract can be used as an anticorrosive additive in the two conditions studied.