BS in Materials Engineering
Materials Engineering Department
This study characterized the oxidation kinetics of two types of ferritic stainless steel foils used as substrates for catalytic converters. Catalytic converters rely on an alumina layer on the surface of the foils, which allows the catalyst to attach to the substrate. Because the alumina layer is so important, this study characterized the weight gain, thickness, and composition of the alumina as it grew at 900°C for up to 400 hours. The two foils characterized were an MK foil, used for gasoline engines, and an EMS foil, used for diesel engines. The MK foil showed a percent weight gain of up to 3.6%, an alumina thickness of up to 6 micrometers and a composition of primarily Al2O3 through the entire oxide. The EMS foil had a percent weight gain of 3.5% and an alumina thickness of 3 microns after 400 hours at elevated temperature. The alumina, where present, contained primarily Al2O3. The EMS foil, though, had sections of iron and chromium oxide growing after 200 hours. These oxides went through the entire foil and would break off easily, which would prevent the foil from acting as a substrate for a catalyst. Overall, the MK foil showed good oxidation characteristics for use as a substrate for catalytic converters, while the EMS should be improved.