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.
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).
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