Esca-Studies of the Structure and Composition of the Passive Film Formed On Stainless-Steels by Various Immersion Temperatures in 0.1 M Nacl Solution

This paper deals with the structure and composition of the passive film formed on the surface of two commercial stainless steels during immersion in 0.1 M NaCl for 0.5 h at 25, 60, and 90°C. The data shows that the passive films formed at 60 and 90°C by short-time solution exposure are very similar to these formed at 25°C, and are consistent with the three-factor model described previously: a hydrated layer in contact with the solution, an oxide layer consisting of iron and chromium oxides having maxima at depths of 3 and 10 Å, respectively, and a metallic layer enriched in nickel. There is a smooth transition between the layers, with the thickness of the outer two layers being about 15 Å

Corrosion of Stainless-Steels in Chloride Solution - An Xps Investigation of Passive Films

Five commercial steels ranging from the martensitic stainless steel containing 12% chromium to the superferrite containing 29% chromium, 4% molybdenum, and 2% nickel have been studied by XPS. In addition, a pure iron-chromium alloy containing 7% chromium has been investigated. Armco iron and pure chromium (99.99%) were included as references. The formation of the passive films (or corrosion) occurred in deoxygenated 0.1 M NaCl solution (pH=5.6), from which the samples were transferred directly to the XPS chamber under controlled atmosphere (Ar). Concentration profiles (at.-%) of the alloy constituents in their oxidized and metallic states have been determined separately from the measured XPS depth profiles. For c≳= 12% chromium the passive films have the following structure: there is a depletion of Cr in the inner region, followed by an enrichment (concentration maximum) in the central region of the films. The height of this maximum increases, and its position shifts towards the surface with increasing chromium content in the alloy. The outermost monolayers are rich in water and hydroxyl groups. Various significant properties of the films change drastically at the critical chromium concentration of about 12%. This behaviour is rather independent of the other components (Mo, Ni, Cu) present in the alloys and is discussed in terms of a phase transition in the films which is controlled by the chromium concentration

Passive Films On Stainless-Steels in Aqueous-Media

The purpose of this paper is to provide a syntheses of experimental results regarding films formed on the surface of stainless steels. Such syntheses are attempted for the environments most studied. In each case the overview is presented with reference to the most important papers. Conflicting data are also presented and discussed. Based on the results of the prior studies, a four region model is proposed to describe the surface passive film and its breakdown