Electrochemical Corrosion Effects of Ethanol Based Fuel on General Aviation Aircraft Fuel System Components
The replacement of lead additives in aviation fuels with non-leaded alternatives is of great interest to the aviation community. Ethanol, which may be derived from renewable resources, has been suggested as an octane-enhancing additive for general aviation fuel. Besides the consideration of the additive?s performance in meeting the requirements of aircraft engine combustion characteristics, there is also a concern about the material compatibility of ethanol fuels with respect to fuel system components consisting of metallic and polymer materials.
This research project focuses on the effects of ethanol based fuels on the corrosion of metal components in fuel systems of general aviation aircraft. The types of metals that are studied include aluminum, brass and steel. Blends of gasoline that were tested were mixed with 10% to 85% ethanol by volume.
The potential for corrosion to occur was determined through conventional weight loss methods and electrochemical measurements. By applying the principles of kinetics to the electrochemical reaction, the rate of corrosion was determined. Potentiodynamic polarization electrochemical techniques were used to determine the corrosion rates of metals exposed to various ethanol based fuels. Tafel extrapolation and linear polarization were correlated to corrosion rates. Impurities of water, chloride ion, and hydrogen ion were studied for their effect on the corrosion rate. Planned-interval tests were performed to investigate the change of the corrosive characteristics of metal and the change of the corrosiveness of the ethanol based fuels. Finally, DCI-11 from Octel-Starreon, was chosen to study the mechanism of commercial corrosion inhibitors.
An observation was made that ethanol based fuels can create corrosion problems to some metal aircraft components. The inhibitor tested was effective in protection for fuel containing high percentages of ethanol. A correlation has been developed between observed metallic corrosion and fuel conductivity. The use of a corrosion inhibitor, conductivity measurements, and non-destructive component inspections should be incorporated in any future regulations intended to approve the use of ethanol based fuels in the existing fleet of general aviation aircraft.
Advisor:Clifford E. George
School:Mississippi State University
School Location:USA - Mississippi
Source Type:Master's Thesis
Date of Publication:11/11/2004