Structure Analysis of Cation Selective Cr-goethite as Protective Rust of Weathering Steel

Abstract

We have performed extended X-ray absorption fine structure (EXAFS) analysis for artificial Cr-goethite to elucidate the local structure around Cr in Cr-goethite. The spectra were obtained using synchrotron radiation X-rays at the Photon Factory in Tsukuba. The first shell contributions were isolated by Fourier filtering the EXAFS data, and the inverse Fourier transformed single-shell data were analyzed using a curve fitting method. The results show that Cr is coordinated with (7±1) O²⁻ ions. The protective characteristics of the Cr-goethite protective rust layer on weathering steel can be interpreted in terms of the O²⁻ coordination around Cr³⁺ resulting in the creation of negative fixed charge in the Cr-goethite particles.