Abstract
Pyrolysis bio-oils are corrosive to low alloy steels, e.g., 2.25Cr-1Mo, 5Cr-1Mo, and 9Cr-1Mo grades. To identify the alloys with sufficient bio-oil compatibility, several commercial stainless steels were examined in bio-oil using electrochemical impedance spectroscopy to semi quantitatively assess their corrosion resistance. Low-Ash Low-Moisture (LALM) bio-oil, produced from a forest residue feedstock by the National Renewable Energy Laboratory in Golden, CO, was used as a test liquid for electrochemical impedance spectroscopy measurements. Three organic corrodents, formic acid, catechol, and lactobionic acid, were added into LALM bio-oil to produce test liquids with intentionally increased corrosivity. Corrosion reaction resistance, determined from the impedance data, was used to evaluate the corrosion compatibility of each stainless steel in LALM bio-oil and LALM bio-oil + organic corrodent(s). The results from corrosion reaction resistance indicated that the critical Cr content of stainless steels for corrosion resistance would be greater than 14 wt % if Ni and Mo contents are low but can be as low as 12–13 wt % with appreciable amounts of Ni and Mo.
