Study of Corrosion Effects of Oxidized Ethanol–Gasoline Blends on Metallic Materials

Bioethanol added into gasolines significantly changes the physical and chemical properties of the resulting fuels and can have a considerable influence on their overall thermo-oxidative stability. During fuel oxidation, different oxidation products such as water, acidic substances, and peroxides are formed and these can have corrosive effects on metallic construction materials of the storage and transportation equipment, engines, and fuel lines of automobiles, etc. In this work, we tested the laboratory prepared ethanol–gasoline blends (EGBs) E10, E25, E40, E60, and E85, which were artificially oxidized depending on their induction period. The oxidized fuels were used to study their corrosion aggressiveness after their thermal load in the presence of oxygen or after the expiry of their shelf life. The corrosion properties of these fuels were tested on steel, copper, aluminum, and brass using electrochemical methods such as electrochemical impedance spectroscopy and Tafel curve analysis. For comparison, static immersion tests on copper and brass were performed. The main parameters for the comparison of the corrosive effects were the instantaneous corrosion rate, the polarization resistance, and the corrosion rates of copper and brass, which were obtained from the weight losses which occurred during the static tests. The highest corrosion aggressiveness was observed, in most cases, for the oxidized E60 fuel; in this environment, the lowest resistance was observed for brass, at a peroxide content of 250 mg·kg–1 already.