Efficiency of Steel Corrosion Inhibitors in an Environment of Ethanol–Gasoline Blends

Ethanol produced from renewable sources (i.e., bioethanol) is a first-generation biofuel that is currently being added as a biocomponent into gasolines. Mixtures of ethanol and gasoline are designated as ethanol–gasoline blends (EGBs). Ethanol has high polarity and moisture affinity, which considerably influence the properties of the resulting EGBs including their aggressiveness to many metallic and nonmetallic materials. The corrosion aggressiveness of EGBs can be minimized by suitable corrosion inhibitors. In this study, we tested three different corrosion inhibitors on mild steel in the environment of aggressive E10, E25, E60, and E85 fuels. The inhibitors tested were diethylene triamine (DETA) and two mixed inhibitors containing propargyl alcohol, dibenzyl sulfoxide, and octadecyl amine. To study the efficiency of the corrosion inhibitors, we used static and dynamic corrosion tests and electrochemical measurements including impedance spectroscopy and potentiodynamic polarization. The highest corrosion aggressiveness on mild steel was observed for the E60 fuel. The highest inhibitory efficiency was, for all the fuels tested, observed for the DETA inhibitor. For the DETA concentration of 100 mg·L–1, the inhibitory efficiency in the E60 fuel was determined to be around 98%.