Direct Visualization of Structures of Atmospheric Corrosion Products on the Steel Surfaces by Two-dimensionally X-ray Absorption Fine Structure

Abstract

In this study, using two-dimensional X-ray absorption fine structure (2D-XAFS), the structures of atmospheric corrosion products on the steel surfaces were observed in the cross-sectional direction. For 2D-XAFS measurement, the sample was sliced from the surface of the rust toward the substrate using a microtome and thinned below 10 µm. In addition, the 2D-XAFS data incorporated an unsupervised learning denoising method based on the Noise2Noise algorithm for achieving high spatial resolutions. The results demonstrate that the structure of the amorphous rust exhibits an α-FeOOH-like structure, and the analysis of the composition ratio of Fe₃O₄, α-FeOOH, and γ-FeOOH revealed the distribution the Fe₃O₄ ratio. This distribution provided compelling evidence for proceedings of the reactions suggested by Evans et al. during the atmospheric exposure test.