Electrochemical Study of Mild Steel Resistance in Butanol-Gasoline and Ethanol-Gasoline Blends

This work deals with studying mild steel corrosion resistance in ethanol-gasoline and butanol-gasoline blends (EGBs and BGBs, respectively) with an alcohol content of 10-100 vol %. These fuels were tested in two forms: pure (noncontaminated) and purposely contaminated with water and trace amounts of acids, chlorides, and sulfate ions. Electrochemical methods, such as open circuit potential, electrochemical impedance spectroscopy, and polarization characteristics measurements in three-electrode arrangements were used for the study. A three-month-long static immersion test was performed as a supplementary method. The obtained results showed that the contamination led to an increase in aggressiveness of the tested fuels against the mild steel. This effect was surprisingly more noticeable for the BGBs, in which the corrosion rate increased by up to 3 orders of magnitude compared with their noncontaminated form. For the EGBs with an ethanol content of 60 vol % or more (E60 and higher), an initial quasi-passive state was observed, which was not persistent. Pitting corrosion was observed especially in the E100 fuel and in the fuels containing 40 vol % or more of butanol (B40 and higher). The EIO and BIO fuels showed very low corrosion aggressiveness even after the contamination. In the B10 fuel, the lowest mild steel corrosion rates were measured, which corresponded to the lowest corrosion current densities (3.6 X 10(-3) mu A cm(-2)) and the highest polarization resistance (13.7 M Omega cm(2)).