Ethanol–gasoline blends (EGBs) can easily absorb large amounts of water because of the presence of ethanol. Acidic compounds and ions can be dissolved in water, and these substances can have corrosive effects on metallic construction materials. With the increasing content of ethanol in fuels, the conductivity and ability of fuel to absorb water increases, and the resulting fuel is becoming more corrosive. In this work, we tested E10, E40, E60, E85, and E100 fuels that were prepared in the laboratory. These fuels were purposely contaminated with water and trace amounts of ions and acidic substances. The aim of the contamination was to simulate the pollution of fuels, which can arise from the raw materials or from the failure to comply with good manufacturing, storage, and transportation conditions. The corrosion properties of these fuels were tested on steel, copper, aluminum, and brass using electrochemical impedance spectroscopy and Tafel curve analysis. For comparison, static immersion tests on steel were also performed. The main parameters for the comparison of the corrosion effects of the tested fuels were the instantaneous corrosion rate; the polarization resistance; and the corrosion rate, which was obtained from the weight loss occurring during the static tests. In most cases, E60 fuel showed the highest corrosion activity.

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Bioethanol added into gasolines significantly changes the physical and chemical properties of the resulting fuels and can have a considerable influence on their overall thermo-oxidative stability. During fuel oxidation, different oxidation products such as water, acidic substances, and peroxides are formed and these can have corrosive effects on metallic construction materials of the storage and transportation equipment, engines, and fuel lines of automobiles, etc. In this work, we tested the laboratory prepared ethanol−gasoline blends (EGBs) E10, E25, E40, E60, and E85, which were artificially oxidized depending on their induction period. The oxidized fuels were used to study their corrosion aggressiveness after their thermal load in the presence of oxygen or after the expiry of their shelf life. The corrosion properties of these fuels were tested on steel, copper, aluminum, and brass using electrochemical methods such as electrochemical impedance spectroscopy and Tafel curve analysis. For comparison, static immersion tests on copper and brass were performed. The main parameters for the comparison of the corrosive effects were the instantaneous corrosion rate, the polarization resistance, and the corrosion rates of copper and brass, which were obtained from the weight losses which occurred during the static tests. The highest corrosion aggressiveness was observed, in most cases, for the oxidized E60 fuel; in this environment, the lowest resistance was observed for brass, at a peroxide content of 250 mg•kg −1 already.

This work deals with studying mild steel corrosion resistance in ethanol–gasoline and butanol–gasoline blends (EGBs and BGBs, respectively) with an alcohol content of 10–100 vol %. These fuels were tested in two forms: pure (noncontaminated) and purposely contaminated with water and trace amounts of acids, chlorides, and sulfate ions. Electrochemical methods, such as open circuit potential, electrochemical impedance spectroscopy, and polarization characteristics measurements in three-electrode arrangements were used for the study. A three-month-long static immersion test was performed as a supplementary method. The obtained results showed that the contamination led to an increase in aggressiveness of the tested fuels against the mild steel. This effect was surprisingly more noticeable for the BGBs, in which the corrosion rate increased by up to 3 orders of magnitude compared with their noncontaminated form. For the EGBs with an ethanol content of 60 vol % or more (E60 and higher), an initial quasi-passive state was observed, which was not persistent. Pitting corrosion was observed especially in the E100 fuel and in the fuels containing 40 vol % or more of butanol (B40 and higher). The E10 and B10 fuels showed very low corrosion aggressiveness even after the contamination. In the B10 fuel, the lowest mild steel corrosion rates were measured, which corresponded to the lowest corrosion current densities (3.6 × 10–3 μA cm–2) and the highest polarization resistance (13.7 MΩ cm2).

Sixteen laboratories have performed electrochemical noise (EN) measurements based on two systems. The first uses a series of dummy cells consisting of a "star" arrangement of resistors in order to validate the EN measurement equipment and determine its baseline noise performance, while the second system, based on a previous round-robin in the literature, examines the corrosion of aluminium in three environments. All participants used the same measurement protocol and the data reporting and analysis were performed with automatic procedures to avoid errors. The measurement instruments used in the various laboratories include commercial general-purpose potentiostats and custom-built EN systems. The measurements on dummy cells have demonstrated that few systems are capable of achieving instrument noise levels comparable to the thermal noise * Corresponding author 1 ISE member 2 of the resistors, because of its low level. However, it is of greater concern that some of the instruments exhibited significant artefacts in the measured data, mostly because of the absence of anti-aliasing filters in the equipment or because the way it is used. The measurements on the aluminium samples involve a much higher source noise level during pitting corrosion, and most (though not all) instruments were able to make reliable measurements. However, during passivation, the low level of noise could be measured by very few systems. The round-robin testing has clearly shown that improvements are necessary in the choice of EN measurement equipment and settings and in the way to validate EN data measured. The results emphasise the need to validate measurement systems by using dummy cells and the need to check systematically that the noise of the electrochemical cell to be measured is significantly higher than the instrument noise measured with dummy cells of similar impedance.