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Oxidation of Metals

, Volume 57, Issue 3–4, pp 193–216 | Cite as

Evidence for Chromium Evaporation Influencing the Oxidation of 304L: The Effect of Temperature and Flow Rate

  • H. Asteman
  • J.-E. Svensson
  • L.-G. Johansson
Article

Abstract

The influence of temperature and flow rate on the oxidation of 304L steel in O2/H2O mixtures was investigated. Polished samples were isothermally exposed to dry O2 and O2+40% H2O at 500–800°C at 0.02–13 cm/sec flow velocity, for 168 hr. The samples were analyzed by gravimetry, XRD, ESEM/EDX, and AES depth profiling. The oxidation of 304L in water vapor/oxygen mixtures at 500–800°C is strongly influenced by chromium evaporation. The loss of chromium tends to convert the protective chromia-rich oxide initially formed into a poorly protective, iron-rich oxide. The rate of oxidation depends on flow rate; high flow rates result in an early breakdown of the protective oxide. The most rapid breakdown of the protective oxide occurs at the highest temperature (800°C) and the highest gas flow (4000 ml/min=13 cm/sec). The oxide formed close to grain boundaries in the metal is more protective, while other parts, grain surfaces suffer breakaway corrosion. The protective oxide consists of a Cr-rich 50–200-nm thick M2O3 film, while the parts experiencing breakaway corrosion form a 10–30-μm thick Fe-rich M2O3/M3O4 scale. The results show that chromium evaporation is a key process affecting the oxidation resistance of chromia formers and marginal chromia formers in O2/H2O mixtures.

oxidation high-temperature corrosion marginal chromia formers water vapor effect chromia evaporation breakaway corrosion temperature dependence flow-rate dependence 304L 

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Copyright information

© Plenum Publishing Corporation 2002

Authors and Affiliations

  • H. Asteman
    • 1
  • J.-E. Svensson
    • 2
  • L.-G. Johansson
    • 1
  1. 1.Department of ChemistryGöteborg UniversityGöteborgSweden
  2. 2.Department of Environmental Inorganic ChemistryChalmers University of TechnologySweden

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