Effect of surface roughness on corrosion behaviour of stainless steel in supercritical CO2

To study the effect of surface roughness on the corrosion behavior of austenitic steels in supercritical CO2, the corrosion experiments were conducted on 304 and 310S stainless steels at 550 °C and 15 MPa. The corroded samples were characterized using XRD and SEM-EDS. The results demonstrate that surface roughness significantly affects the morphology and structure of the oxide films formed on 310S stainless steel. Samples prepared with varying surface roughness (grounded using from 200# to 1000# metallographic abrasive papers) showed that rougher surfaces tend to develop denser oxide layers, whereas smoother surfaces exhibit relatively loose and porous oxide films. Despite these differences in oxide structure, the overall corrosion weight gain remained largely unaffected, indicating minimal oxide shedding from 310S steel. The oxidation product is mainly Cr2O3. For 304 stainless steel, surface roughness was found to influence the composition of surface oxides. Both 200# and 1000# samples formed loose, porous oxide films prone to spallation, with the primary constituents being Fe3O4, (Fe, Cr)3O4 and Fe2O3. Because the content of (Fe, Cr)3O4 and Fe3O4 of the former is higher, more voids appear in the oxide film, leading to spallation within the first 100 h of exposure. The rougher surface showed a more pronounced loss of oxide. But for the 600# sample, the main component is Fe2O3. Carburization was observed to intensify with increasing surface roughness in both materials. Notably, the 200# sample of 310S stainless steel exhibited more severe carburization compared to the 1000# sample of 304 stainless steel.