Corrosion Performance of Stainless and Carbon Steels in Pyrolysis Oil: The Role of Acid Number on Corrosion Rates

Abstract This study explored the corrosion behavior of A516-70 carbon steel and SS304 stainless steel under conditions relevant to fast pyrolysis oil storage and transportation. Both materials were subjected to immersion tests at 80°C for seven days to simulate real-world exposure to pyrolysis oil. A516-70 exhibited severe corrosion, with rates as high as 7.1 mm per year, highlighting its limitations in such environments. In contrast, SS304 maintained excellent corrosion resistance throughout the test, indicating it is better suited for these applications. The corrosion layers formed on A516-70 were primarily composed of iron oxides, such as Fe₂O₃, whereas SS304 developed a protective film containing chromium-rich oxides. Three types of pyrolysis oil has been tested in this study and the high acidity of the pyrolysis oil, reflected in its low pH and elevated total acid number (TAN), was identified as the main driver of material degradation. Further microscopic analysis will be conducted to gain deeper insights into the mechanisms of corrosion, supporting efforts to enhance material durability and optimize reactor design for long-term industrial use.