Electrochemical corrosion tests in an environment of low-conductive ethanol-gasoline blends: Part 1 – Testing of supporting electrolytes

Abstract

Bioethanol is a promising biofuel that can be used in the pure form or in the form of ethanol-gasoline blends (EGBs) as a transportation fuel. The combustion of bioethanol in petrol engines is associated with several problems, with bioethanol corrosion effects on metallic construction engine parts being one of the most serious ones. Electrochemical methods, such as electrochemical impedance spectroscopy, measurement of polarization characteristics (Tafel scan), etc., have been found to be efficient in studying corrosion effects in metal-EGB systems. However, a fuel environment with a low ethanol content (such as E10 and lower) has low conductivity, which can be a limiting factor for electrochemical corrosion studies. Supporting electrolytes can be used to increase the conductivity of such environments. These supporting electrolytes must be inert against the occurring corrosion reactions in order not to negatively affect the obtained corrosion data. In this work, we tested four potential supporting electrolytes (lithium perchlorate, tetrabutylammonium tetrafluoroborate, potassium hexafluorophosphate, and tetrabutylammonium bromide) to be used for the electrochemical corrosion tests on mild steel in the environment of an E85 fuel. In our study, we demonstrated that tetrabutylammonium tetrafluoroborate (TBATFB) can successfully be used for short-term corrosion studies as it exhibited minimum effects on the obtained electrochemical data even at a relatively high concentration of about 500 mg/L. The use of this supporting electrolyte can substantially facilitate electrochemical corrosion studies in less conductive media such as EGBs with a low content of ethanol. • Corrosion behavior of mild steel in the environment of E85 fuel was tested. • Electrochemical impedance spectroscopy and Tafel scan were used as testing methods. • Applicability of four supporting electrolytes for the testing methods was studied. • TBATFB was found to be usable for short-term corrosion studies by the testing methods.