Effect of Natural Substances as Antioxidants and as Corrosion Inhibitors of Carbon Steel on Soybean Biodiesel

Abstract The use of natural additives in biodiesel has been investigated, however, there is limited information in the literature in relation to their influence on corrosion resistance and oxidative stability. This work aims to investigate the oxidative stability of biodiesel and the corrosion resistance of carbon steel (AISI 1020) in contact with soybean biodiesel solutions (B100) in the presence and absence of natural additives such as: rosmarinic acid, curcumin, gingerol, eugenol, thymol and quercetin. Corrosion and microscopy tests were used to assess corrosion resistance. The Rancimat technique was used to study oxidative stability. The results obtained indicate that curcumin was the best additive in relation to oxidative stability, while rosmarinic acid showed better performance in inhibiting corrosion. The effect of these substances is related to the presence of phenolic compounds or the existence of oxygen in its molecular structure.