Abstract
The role of ethanol (C2H5OH) in pitting corrosion behavior of AISI 316L austenitic stainless steel was investigated in aqueous ethanolic solution with chloride. The pitting susceptibility and surface morphology of 316L in a series of ethanol-containing solutions were examined using X-ray photoelectron spectroscopy (XPS), optical microscopy with 3D stitching, immersion tests, and potentiodynamic polarization measurements. Results demonstrated that the ethanol concentration impacted little on the passive film stability while it dramatically influenced the pitting corrosion susceptibility. Corrosion rate of 316L after immersion tests first increased and then decreased as the concentration of ethanol increased from 0 to 10 M in ferric chloride solution. This, however, did not correspond to the breakdown potential which directly decreased from 489 to 249 mV as the water concentration decreased in ethanolic NaCl solutions. The pits density after both immersion and electrochemical tests showed that the initiation of pitting in ethanolic solution tended to occur at multiple points at the same time. The synergy effect on pitting behavior of hydrolysis enhancement and solubility reduction of metal cations due to the introduction of ethanol has also been discussed.
Highlights
Bioethanol has been widely recognized as a promising renewable sustainable biofuel to replace diminishing petroleum-based fuel in existing combustion motor system
Since the passivation of stainless steel would fail in anhydrous solutions with water less than 70 mole % (Kelly and Moran, 1990), solutions with ethanol content from 0 to 10 M were applied to ensure that changes of corrosion resistance are not caused by extremely low water content, The goal of the work is to clarify the influence of ethanol on passivation, pitting sensitivity and pits morphology
The results proved that the passive film on stainless steel was slightly deteriorated
Summary
Bioethanol has been widely recognized as a promising renewable sustainable biofuel to replace diminishing petroleum-based fuel in existing combustion motor system. Regular crops such as corn and sugarcane, due to their chief value in food reserves, are unable to meet the increasing worldwide demand of fuel-grade ethanol. Coating is a widely used method to enhance corrosion resistance. Blunt materials such as epoxy (Bisht et al, 2017), graphite (Wang et al, 2019), alumina (Sun et al, 2019), and polyaniline (Lei et al, 2020) are often recommended. It is necessary to study the corrosion behavior of traditional stainless steel for bioethanol fermentation tanks, such as AISI 316L stainless steel, which is still widely used in the production of bioethanol, in ethanolic solutions
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