Session: Corrosion in the Biofuel and Biomass Industry
Corrosion Resistance of UNS S31740 in High-Temperature Bio Oil Environment (C2026-00106)
Monday, March 16, 2026
8:00 AM - 8:30 AM Central
Location: 371 AB
Earn .5 PDH
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Applying conventional molybdenum-added stainless steels such as UNS S31603 and UNS S31703 are effective in most naphthenic acid corrosion (NAC) environments. However, there is the risk of polythionic acid stress corrosion cracking (PTA-SCC) due to sensitization during long-term service at high temperature. UNS S31740 (17Cr-14Ni-3Mo-0.3Nb-N, ASME Code Case 3038) with extremely low carbon and high nitrogen contents has superior resistance toward both NAC and PTA-SCC. S31740 is contributing to safety operations of distillation units in conventional refineries.As you know, the importance of bio-refinery is increasing day by day to achieve carbon neutrality.Considering the above, this study focuses on evaluating the corrosion resistance of S31740 in a high-temperature bio-oil environment. Corrosion tests were conducted for 48 hours in two different media: distillers corn oil and tall oil fatty acid. The corrosion rate of S31740 was found to be at least an order of magnitude lower than that of the baseline UNS S30403, particularly under more corrosive conditions. This superior performance is due to the 3% molybdenum addition, which enhances the corrosion resistance of both S31740 and S31703 compared to S30403. Furthermore, S31740 also demonstrates excellent resistance to sensitization, making it a particularly suitable material for high-temperature bio-oil applications.
