Emissions control catalysts: Links between Fecralloy preoxidation and coating adherence

Tightening emissions legislation for vehicles across the world has caused the use of monolith catalysts in automobile emission control to become ubiquitous. In this study, the physiochemical transformations caused by thermal pre-oxidation of the surface of Fecralloy® foil, an integral component of emissions control catalysts, have been studied to assess their role on coating film adherence. The foil coupons were pre-oxidised at 950°C for 0, 5, 10 and 30 h and the mass gain was found to fit a simplified hyperbolic model. Measurements were made of surface topography and microstructure using laser profiling interferometry (LPI) and scanning electron microscopy (SEM), with phase analysis being obtained from X-ray diffraction (XRD). The optimal surface roughness was obtained after 10 h of pre-oxidation, when the surface contained significant amounts of α-alumina arranged as randomly oriented whiskers. Upon coating of the treated foil coupons with γ–alumina slurry, the sample pre-oxidised for 10 h gave the best performance in terms of coating film loading of 7.94 mass % and adherence of less than 10 mass % loss