High-temperature corrosion steels

Ferritic stainless steels depend on chromium for high temperature corrosion resistance. A Cr202 scale may form on an alloy above 600°C when the chromium content is ca 13 wt % (36,37). This scale has excellent protective properties and occurs iu the form of a very thin layer containing up to 2 wt % iron. At chromium contents above 19 wt % the metal loss owiag to oxidation at 950°C is quite small. Such alloys also are quite resistant to attack by water vapor at 600°C (38). Isothermal oxidation resistance for some ferritic stainless steels has been reported after 10,000 h at 815°C (39). Grades 410 and 430, with 11.5—13.5 wt % Cr and 14—18 wt % Cr, respectively, behaved significandy better than type 409 which has a chromium content of 11 wt %. 

The extent to which low alloy steels react to high temperature corrosive environments is the subject of this chapter. In view of the commercial importance of these steels, the published literature on this topic is extensive and is being continually enlarged. The reader is encouraged to refer to the many excellent papers and current issues of the journals, referenced at the end of the chapter, for more detailed and contemporary information on the topic. 

If local stresses exceed the forces of cohesion between atoms or lattice molecules, the crystal cracks. Micro- and macrocracks have a pronounced influence on the course of chemical reactions. We mention three different examples of technical importance for illustration. 1) The spallation of metal oxide layers during the high temperature corrosion of metals, 2) hydrogen embrittlement of steel, and 3) transformation hardening of ceramic materials based on energy consuming phase transformations in the dilated zone of an advancing crack tip. 

Lai, G. Y. (1990) High Temperature Corrosion of Engineering Alloys (ASM International). Landels, H. H. and Stout, E. (1970) Brit Chem Eng. 15, 1289. Glassed steel equipment A guide to current technology. 

Monoliths made out of metal were introduced to the market to some extent as an alternative to ceramic supports. As shown in Fig. 33, these supports consist of a metallic outer shell, in which a honeycomb-like metallic structure is fixed. The honeycomb is formed by alternate flat and corrugated thin metal foils (Fig. 34). These foils are made out of corrosion- and high-temperature-resistant steel, and are about 0.05 mm thick. 

B.J. Smith, C.P. Erskine, R.J. Hartranft, A.R. Marde, High-temperature corrosion-fetigue (circumferential) cracking Hfe evaluation procedure for low alloy (Cr-Mo) boiler mbe steels. Mater. Charact. 34 (1995) 81-86. 

T. Sundararajan, S. Kuroda, J. Kawakita, S. Seal, High temperature corrosion of nanoceria coated 9Cr-lMo ferritic steel in air and steam. Surf Coat. Tech. 201 (2006) 2124-2130. 

M.A. Uusitalo, P.M.J. Uuoristo, T.A. Mantula, High temperature corrosion of coatings and boiler steels in reducing chlorine-containing atmosphere. Surf. Coat. Tech. 161 (2002) 275-285. 

M. Fukumoto, C. Tachikawame, Y. Matsuzaka, M. Hara, Formation of Si diffusion layer on stainless steels and their high temperature corrosion resistance in molten salt, Corros. Sci. 56 (2012) 105—113. 

F.J. Perez, E. Otero, M.P. Hierro, C. Gomez, F. de Pedtaza, J.L. Segovia, E. Roman, High temperature corrosion protection of austenitic AISI304 stainless steel by Si, Mo and Ce ion implantation. Surf. Coat. Tech. 108-109 (1998) 127-131. 

Three methods are available for the prevention of high-temperature corrosion, including the removal of harmful components from the fuels, the use of steel alloys with improved resistance to the corrosion, and the use of some additives to the fuel. Magnesium compounds are the most used additives in this respect. Magnesium oxide will react with the ash materials to produce high-melting products. 

IRRAS can be extremely useful for studying in situ the corrosion and anticorrosion mechanisms [295]. For example, in order to understand high-temperature corrosion processes on AISI type 304 stainless steel, Guillamet et al. [284] measured the spectra by IRRAS of a steel plate exposed for 1 min to air at high temperatures. Comparison with the vlo bands of a series of oxides indicated that the main product is a-Fc203 (not Fc304, as suggested earlier for corrosion of... 

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