Structural Analysis of Native Passive Films on Stainless Steels Using Synchrotron X-ray Spectroscopy

Abstract

A native passive film is formed on the SUS304 surface at ordinary temperature and pressure 1, 2. As a structural model of the film, a network-structure composed of Cr-oxide and-hydroxide has ever been proposed 1, 3 , but experimental evidences for the structure have not been reported yet. We examined the detailed film structure using synchrotron X-ray absorption fine structure (XAFS) and X-ray photoelectron spectroscopy (XPS). The XAFS spectra clearly showed an ordered network-structure (at least 10) of Cr(IV) oxide. Additionally, the XPS spectra indicated that the chromium oxide is transformed into a chromium oxyhydroxide such as a-O-Cr-OH-structure. These results are the first evidence that the network structure exists actually in the native passive film of SUS304.

Aichi Synchrotron Radiation Center for Industrial Use

“…Figure 8 shows a new structural model of the native passive film on the SUS304 substrate obtained by the experiments described above. The left and right figures show a Cr-terminated structure and an OH/O terminated one, respectively [6].…”