Korrosionsverhalten feuerfester Baustoffe in Schlacken unter dem Einfluß elektrischer Felder

Translated title of the contribution: Corrosion Behavior of Refractory Materials in Slags under the Influence of Electric Fields

Robert Breyner

Research output: ThesisDoctoral Thesis

Abstract

The investigation of the electrochemical corrosion of refractories in the vicinity of the slag band and the survey of possible countermeasures were the purpose of this doctoral thesis. Tafel measurements confirmed the nearly exclusive occurrence of electrochemical corrosion at the three-phase-boundary, although the changing surface of the ceramic electrodes prevented the direct determination of electrochemical wear. The main part of this work was concerned with the polarization of several electrode materials in different slags. Through the application of low voltages two main protective mechanisms based on local slag-alterations were identified. Due to the ionic nature of slags the fast migration of very mobile species, e. g. calcium ions, led to their accumulation at the boundaries of the cathode. In CAS-slag, this caused the complete solidification of the melt surrounding the cathode, providing complete protection. Additionally, the observed voltage- and temperature-dependent formation of dicalciumsilicate and lime in the pores was a consequence of ion-diffusion in solid matter. The second protective effect occurred in silicate slags with high contents of oxides of polyvalent elements. Wustite was reduced to metallic iron, which resulted in an increased silicate-content of the remaining melt and caused the formation of a highly viscous slag layer surrounding the cathode. A successful application of this mechanism required a nearly complete absence of, compared to Fe2+, more noble metal ions and ferric iron. In this work it could be demonstrated, however, that the application of low electric voltages permits the protection of ceramic materials under appropiate conditions.
Translated title of the contributionCorrosion Behavior of Refractory Materials in Slags under the Influence of Electric Fields
Original languageGerman
QualificationDr.mont.
Supervisors/Advisors
  • Mori, Gregor Karl, Co-Supervisor (internal)
  • Harmuth, Harald, Assessor A (internal)
Publication statusPublished - 2009

Bibliographical note

no embargo

Keywords

  • corrosion
  • refractories
  • polarization
  • protection

Cite this