Corrosion assessment of metals in bioethanol-gasoline blends using electrochemical impedance spectroscopy

Due to the increased use of environmentally friendly fuels, it becomes imperative to evaluate the impact of biofuels on the performance of materials used in auto parts. The corrosive effects of biofuels are important in terms of durability of auto-parts since there is an evidence of the increasing deterioration in automobile parts with the long-term use of biofuels. In this research, the behavior of metals, used in the manufacturing of auto parts, in pure bioethanol (E100) and bioethanol-gasoline blends with 30% (E30), 50% (E50), and 85% (E85) of ethanol content were evaluated. Electrochemical impedance Spectroscopy (EIS) curves were done under static conditions at 45 °C. The metallic materials evaluated were stainless steel, tin, carbon steel and copper. The EIS diagrams showed two capacitive arcs for all materials. The high frequency arc was related to the dielectric response of the fuel blends, while the second one shows the characteristics and activity of the metal/fuel interface. According to the transfer resistance (Rt) obtained from the second arc of the EIS measurements, copper and carbon steel exhibited corrosion susceptibility in all fuel blends, while stainless steel and tin showed good anticorrosion behavior by showing high Rt values. The highest charge transfer resistance was showed by tin, followed by stainless steel, carbon steel and copper. Except for carbon steel and copper, the other set samples were compatible with the evaluated blends.