Oxidation iron-chromium alloys

Turner, D.J., C.E.R.L. Note, 1979, draft "Thermodynamics and the Nature of Oxides Formed on Iron-Chromium Alloys"... 

Asami, K. Hashimoto, K. Shimodaira, S. (1978) XPS determination of composition of alloy surfaces and surface oxides on mechanically polished iron chromium alloys. Corrosion Sci. 18 713-723... 

Concentrated sulphur acid evaporation and dehydration is performed in a group of two heat exchangers with important exchange surface (up to 1 340 m2) (HX-208). The S03/S02 decomposition reactor (HX-209) is a set of five reactors with two reactive zones. The first one, with a temperature of 875 K requires a platinum catalyst and the second one an iron-oxide catalyst. The operating temperature in the second zone increases up to 1125 K. Due to operating conditions (temperature, chemical composition), these three devices require a nickel-iron-chromium alloy. Then sulphur trioxide recombination reactor consists of a packed column (HX-210). Required investment for S03 conversion is estimated about EUR(08) 508.6 M. 

E6.2. Predict whether or not galvanic corrosion will cause the following alloys to be subjected to leaching (i) carbon and carbon steel alloys in an oxidizing atmosphere, (ii) steel rivets in aluminum drain gutters, (iii) copper-nickel alloy in refinery condenser tubes, (iii) graphite fiber-reinforced aluminum composites, (iv) brass in water, (v) iron-chromium alloys, and (vi) carbon steel pipe in contact with the weld to stainless steel pipe. 

The breakdown of chromized coatings during oxidation has been attributed in part to the phenomenon of secondary diffusion, which decreases the chromium concentration at the metal surface. The mechanism of oxidation is therefore complex [167], although probably similar to that of iron chromium alloys, a subject that has been reviewed by Wood [168], among others. Protection is therefore dependent on the formation of a coherent barrier scale or, in the case of carbon steels, a carbide diffusion barrier. 

The composition of an oxide film formed on an iron-chromium alloy is studied by XPS. The thickness of the film is equal to 2 nm, and it is covered with a monolayer of carbon because of contamination. The atomic radius of carbon is equal to 0.09 nm, the escape depth of photo-electrons for trivalent chromium ions in both the oxide and in the contamination layer is 1.9 nm. Calculate the attenuation of the Cr signal by the carbon film. 

These data are important to the development of a full understanding of the properties of the passive layers. The resistance of the iron-chromium alloys to passivity breakdown and localized corrosion can be improved by prolonged polarisation, which is directly related to the Cr enrichment in the oxide layer (5). 

Mikkelsen, L. (2003). High Temperature Oxidation of Iron-Chromium Alloys, (Ph.D. Thesis, Riso National Laboratory Roskilde, Denmark, Date of access 20 of August 2011, Available at http //130.226.56.153/rispubl/reports/ris-phd-2.pdf... 

HUNTINGTON alloy HA-330 A nickel-iron chromium alloy with good high-temperature strength and corrosion resistance. Provides good resistance to oxidation and carburization. 35.5 44.0 18.5 A NR X A G-E G-E A A A G-E... 

Iron-chromium alloys temperatures High-temperature oxidizing Chromium, which forms a... 

Iron-chromium alloys High-temperanire oxidizing atmospheres Cbromiiun, which forms a protective film... 

Description and corrosion resistance. Alloy 800 is a nickel-iron-chromium alloy with good strength and excellent resistance to oxidation and carburization in high-temperature atmospheres. It also resists corrosion by many aqueous environments. 

Description and corrosion resistance. Incoloy 825 is a nickel-iron-chromium alloy with additions of molybdenum and copper. It has excellent resistance to both reducing and oxidizing acids, stress-corrosion cracking, and localized attack such as pitting and crevice corrosion. The alloy is especially resistant to sulfuric and phosphoric acids. 

Caplan D, Cohen M (1952) High temperature oxidation of some iron-chromium alloys. J Met 4 1057-1065... 

Abstract We hypothesised that a nanostructure can bring about dramatic improvements in the oxidation resistance of low chromium iron-chromium alloys at moderate temperatures. A nanocrystaUine Fe-10wt%Cr alloy was foimd to undergo oxidation at a rate that was an order of magnitude lower than its microcrystaUine counterpart. Importantly, the oxidation resistance of nanocry staUine Fe-10wl%Cr alloy was comparable to that of the common corrosion-resistant microcrystalline stainless steels. We outline the difficulties in processing nanocrystaUine iron-chromium ferritic alloys as well as the success in circumventing them. The recently reported roles of nanocrystalline structures in oxidation resistance of a few other systems are also considered. 

Figure 30 shows an example. The sample is an iron/chromium alloy that had been exposed to an aqueous solution of sulfuric acid. The alloy is covered by a surface layer of approximately one nanometer that consists of oxides and hydroxides of iron and chromium. The composition of the material immediately underneath the passive film equals the bulk composition. This is not always the case, as elements are often depleted underneath the passive film if an enrichment of these elements occurs in the film. Technical problems with this kind of investigation mainly concern the transfer of the corroded sample into the vacuum of the spectrometer. Passive layers that contain hydroxides in solution especially tend to degrade in the vacuum. 

Fujii C T and Meussner R A (1964), The Mechanism of the High-Temperature Oxidation of Iron-Chromium Alloys in Water Vapor, JElectrochem Soc, 111, 1215-1221. 

The metal has unusual superconductive properties. As little as 1 percent gadolinium improves the workability and resistance of iron, chromium, and related alloys to high temperatures and oxidation. 

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