Effect of Inert Gases (Pure Nitrogen, Nitrogen and Carbon Dioxide Mixtures) on the Corrosiveness of Anhydrous Ethanol (E100)

The objective of this work was to study the effect of inert gases (pure nitrogen, nitrogen and carbon dioxide mixtures) on the corrosiveness of ethanol fuel through laboratory immersion tests. Initially, preliminary tests were conducted in order to establish the test conditions which showed that inerting tests must be done in hermetic vessels. After the development of the methodology, seven different ethanols (produced from sugar cane and from corn) were tested. Based on the results of this study, it was concluded that when the ethanol is noncorrosive in the presence of pure nitrogen, the presence of carbon dioxide doesn´t cause any deleterious effect, but when the ethanol is corrosive in the presence of pure nitrogen, the presence of carbon dioxide in the inert gas increases the corrosion process (the higher the CO₂ content the higher the surface attack). The water content has an important effect over the corrosion intensity: an increase on the water content increases the corrosion intensity. The presence of crevices has a huge importance, when they are present corrosion is verified even if the test was conducted in a noncorrosive ethanol medium. Finally, mass loss and corrosion rate are not recommended to be used to differentiate the aggressiveness of different ethanols, in short-term tests, as the obtained values are within the experimental error ranges. The test results are evaluated by coupons surface examination; pit density determination (number of pits per unit area); medium test acidity determination and the exam of the medium test color, in order to verify any color change.