Electrochemical evaluation of the influence of low water contents on corrosion in ethanol and hydrocarbon mixtures

Abstract

Many studies investigated corrosion mechanisms in ethanol but their findings might not always be extended to bioethanol-based fuels, where dehydrated ethanol is mixed with 15% or larger amounts of conventional gasoline. This report describes how a 3-electrode electrolytic cell was used to study the effect of water on low carbon steel corrosion in fuel-like ethanol mixtures with hydrocarbons. The electrolyte EHX was prepared by mixing dehydrated ethanol with n-heptane and xylenes at a ratio, which addressed the octane number of retail fuels. Open Circuit Potential (OCP) and Electrochemical Impedance Spectroscopy (EIS) results revealed that addition of water to EHX reduced the solution resistance in general. However, 1% or less water did not accelerate corrosion, despite sig­nif­icant changes in EIS patterns throughout the course of immersion up to 172 h. Addition of 4% water dramatically increased steel corrosion, justifying the need for tight control of water contents in bioethanol fuels. Electrochemical data after 6 h immersion correlated quite well with the EIS, OCP and visual observations performed after 172 h. This suggests that the employed technique is capable of rapid screening of various formulations for biofuels like E85, which might greatly assist industrial research.