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The Influence of Oxide-Scale Microstructure on KCl(s)-Induced Corrosion of Low-Alloyed Steel at 400 °C

Authors
  • Olivas-Ogaz, Mercedes Andrea1
  • Eklund, Johan1
  • Persdotter, Amanda1
  • Sattari, Mohammad2
  • Liske, Jesper1
  • Svensson, Jan-Erik1
  • Jonsson, Torbjörn1
  • 1 Chalmers University of Technology, Department of Chemistry and Chemical Engineering, Environmental Inorganic Chemistry, High Temperature Corrosion Center, Gothenburg, 41296, Sweden , Gothenburg (Sweden)
  • 2 Chalmers University of Technology, Department of Physics, Materials Microstructure, Gothenburg, 41296, Sweden , Gothenburg (Sweden)
Type
Published Article
Journal
Oxidation of Metals
Publisher
Springer US
Publication Date
Nov 27, 2018
Volume
91
Issue
3-4
Pages
291–310
Identifiers
DOI: 10.1007/s11085-018-9881-2
Source
Springer Nature
Keywords
License
Green

Abstract

The high-temperature corrosion of low-alloyed steels and stainless steels in the presence of KCl(s) has been studied extensively in the last decades by several authors. The effect of KCl(s) on the initial corrosion attack has retained extra focus. However, the mechanisms behind the long-term behavior, e.g., when an oxide scale has already formed, in the presence of KCl(s) are still unclear. The aim of this study was to investigate the effect of the microstructure of a pre-formed oxide scale on low-alloyed steel (Fe–2.25Cr–1Mo) when exposed to small amounts of KCl(s). The pre-oxidation exposures were performed at different temperatures and durations in order to create oxide scales with different microstructures but with similar thicknesses. After detailed characterization, the pre-oxidized samples were exposed to 5%O2 + 20%H2O + 75%N2 (+KCl(s)) at 400 °C for 24, 48, and 168 h and analyzed with scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and focused ion beam. The microstructural investigation indicated that Cl-induced corrosion is a combination of oxide thickness and microstructure, and the breakaway mechanism in the presence of KCl(s) is diffusion-controlled as porosity changes prior to breakaway oxidation were observed.

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