Bio-oils derived from biomass contain organic species and acids that can be corrosive to steel-based structural materials used for pipelines and storage tanks. It is, therefore, important to assess corrosivity of organic constituents in bio-oils and identify ferrous alloys with sufficient corrosion resistance. In this work, lactobionic acid, formic acid and catechol were selected as corrosive constituents in bio-oils and used to formulate simulated bio-oils 4 ferrous alloys, including 2.25Cr-1Mo steel and type 410, 201 and 316L stainless steels, were tested by Electrochemical Impedance Spectroscopy (EIS) and potentiodynamic polarization. The corrosivity of each simulated bio-oils was assessed using R2, a charge transfer limiting resistance fitted from EIS spectra. While 2.25Cr-1Mo steel exhibited active corrosion with low R2 values, the stainless steels showed high R2 values associated with passive state. The values of R2, considered proportional to the protectiveness of the passive film, appeared lower in lactobionic acid than in the other simulated bio-oils for the stainless steels, suggesting that lactobionic acid could be more aggressive to passive film than the other constituents of bio-oils. The overall goal of this work is to systematically study the impact of selected bio-oil constituents on corrosion of candidate structural materials for bio-oil production, transport, and storage, as well as provide feedback for potential optimization of bio-oil chemistries to reduce the risk of corrosion.
Biomass-derived oils have gained considerable interest as a renewable energy source to decrease the use of fossil fuels. These bio-oils commonly contain water and organic acids which could cause corrosion of steel-based structural materials.1-4 In a previous study, formic acid in raw bio-oils was reported to corrode low alloy steels and produce iron formate as a corrosion product.5-7 Another lab study compared the corrosion of a plain steel and stainless steels in condensed formic and acetic acids at 60°C and showed that stainless steels were not attacked by the condensate.8 This result suggests that stainless steels could provide sufficient corrosion resistance in bio-oils. However, it is also reported that raw bio-oils at 50°C caused corrosion mass loss in type 409 stainless steel, but not in 304L and 316L austenitic stainless steels, indicating that not all stainless steels are immune to corrosion in bio-oils.7