XPS fast depth profile of the native oxide layers on AISI 304, 316 and 430 commercial stainless steels and their evolution with time

Abstract

The thin oxide layers forming on the metal surfaces of metals determine their interactions with the environment and have a strong influence on the materials properties such as corrosion resistance. Such oxide layers typically have a thickness in the range of a few nanometres, which is a challenge for the analysis of their chemical nature and structure. To characterize such materials and surfaces, XPS using depth profile sputtering is a sensitive and powerful technique. However, it is rather elaborate and raises the risk of changing the nature of the surface layer during the analysis process. This work reports on a protocol for a faster approach to depth profile X-Ray photoelectron spectroscopy (XPS) analysis to obtain accurate and reproducible information on the oxide layer structure by using the snapshot mode of the XPS instrument. This protocol is applied to three stainless steels differing by their chemical composition: FeCr AISI 430, FeCrNi AISI 304 and the chemically more complex FeCrNiMo AISI 316. The respective oxide layer structures observed using this methodology are consistent with literature data. In addition, the structures have been confirmed using non-destructive techniques such as angle-resolved XPS (AR-XPS) and Hard XPS (HAXPES). Finally, the analysis protocol has been applied to obtain information on the evolution of the surface chemistry of those stainless steel grades resulting from mechanical polishing and subsequent aging in contact with atmosphere.