Abstract:

As the energy sector transitions from fossil-based to renewable, biomass-derived feedstocks, crude vegetable oils (CVOs) are increasingly employed as precursors for high-quality drop-in fuels such as sustainable aviation fuel (SAF) and renewable diesel. Although previous studies have shown that the corrosivity of model CVOs in refinery environments correlates strongly with their free fatty acid (FFA) content, the long-term corrosivity of real, industrial-grade CVOs under storage and processing conditions remains poorly constrained. Addressing this gap is essential for ensuring safe integration of CVOs into existing refinery infrastructure.
In this study, two representative industrial-grade CVOs, degummed canola and soybean oil, were subjected to steel immersion corrosion tests at refinery-relevant temperatures (200, 300, and 400 °F) for exposure durations of 1, 10, and 25 days. Corrosion rates of two commonly used refinery construction materials, carbon steel (CS A36) and stainless steel (SS 304L), were periodically monitored to assess material performance as a function of temperature and time. Across all test durations, both CVOs cause no measurable corrosion of SS 304L at 200-400 °F. In contrast, CS A36 exhibited no detectable corrosion at 200 and 300 °F but experienced a remarkable increase in corrosion rate at 400 °F, reaching 0.125 mm/yr in canola oil and 0.054 mm/yr in soybean oil, transitioning from negligible attack to unacceptable uniform corrosion accompanied by pitting.
These findings suggest that stainless steel is preferred for heating elements and high-temperature handling of CVOs, while carbon steel remains appropriate for low-temperature storage and transfer systems. Additional investigation at intermediate temperatures, particularly around 350 °F, is recommended to more precisely define safe operating limits for refinery materials in biofuel processing applications.

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Prof. Nobuo Maeda