Influence of microgeometry of iron surface on the oxidation process – A comparison of multiscale geometric methods and their applicability.

• Sand-blasting causes formation of mixed Al/Fe oxide after oxidation of pure iron. • Increasing of surface roughness has greater impact on oxidation rate at 700 °C. • Multiscale analysis can be used in description of surface roughness prior oxidation. • Data for surface description may be derived by profilometer and by image analysis. • Gleason's method cannot be used in the characterization of curvature prior oxidation. In this paper, an investigation of the effect of surface roughness on oxidation of polished, ground and sand-blasted samples made of iron exposed at 700 and 750 °C for 2 h in air is reported. Surface roughness was described by the 2D data sets obtained by contact profilometer and derived from microphotographs taken at three different magnifications: 100×, 200× and 500×. Surface roughness and curvature were measured by means of conventional and multiscale analysis. Oxidation behavior was analyzed in terms of mass change and SEM/BSE (scanning electron microscopy/backscattered electrons) observations. The oxidation kinetics was found to be influenced by initial surface roughness, however, its effect was different at 700 °C and 750 °C as the contribution of surface diffusion is greater at the lower temperature. It was also concluded that multiscale analysis can be successfully applied in describing surface roughness prior to high-temperature oxidation processes. The most adequate results were obtained from the data derived by contact profilometer and from microphotographs taken at the highest magnification. [ABSTRACT FROM AUTHOR]