Desenvolvimento de aditivos naturais para aprimoramento das propriedades antioxidantes e anticorrosivas do biodiesel de soja

Abstract

Biodiesel is a renewable fuel and, when of vegetable origin, works as an ally in capturing CO2, arising from the burning of fuels. However, it is susceptible to contamination by air humidity, microorganisms, traces of metals and other impurities, altering its initial properties. For example, the use of degraded biodiesel in contact with metal parts and structures of automotive systems can cause corrosion. As a solution, additives with antioxidant and anticorrosive effects are added to improve the quality of this fuel. The effect of additives on the oxidative stability and corrosion resistance of metals in biodiesel has been widely investigated in academic literature, but there is limited information on the effect of additives of natural origin, from plant extracts, on increasing the corrosion resistance of metal in biodiesel. The present work aims to investigate the effect of multifunctional additives such as: extracts of rosemary, turmeric, ginger, stonebreaker and thyme, added to soy biodiesel (B100) in relation to corrosion and oxidative stability in contact with carbon steel (AISI 1020) pure, coated with zinc by electrodeposition and the same coating immersed in oxalic acid. The effect of additives on the corrosion resistance of steel was evaluated by immersion tests in B100 at 25 °C, electrochemical tests, X-ray diffraction (XRD), optical and scanning electron microscopy (SEM). The study of additives on oxidative stability was carried out by obtaining the induction period (IP) using the Rancimat method. The results obtained indicate that the additives analyzed increase the oxidative stability of biodiesel, in addition to acting to inhibit corrosion. Turmeric extract was the best additive in relation to oxidative stability, causing a 92% increase in the biodiesel induction period. Regarding corrosion, the ginger extract was the one that presented the best performance in the general average, where for the steel substrate it obtained an increase of 55.8% in corrosion efficiency, in the steel with zinc coating it obtained 94% and with treatment in oxalic acid it obtained 95.6%. It is concluded that the effect of additives on oxidative stability and corrosion inhibition is related to the existence of oxygen and phenolic compounds present in the molecular structure of natural substances.