The Effect of Temperature on the Corrosion Behavior of 625 Superalloy in PbSO4-Pb3O5-PbCl-ZnO Molten Salt System with 10 wt. % CdO

E. Mohammadi Zahrani, A. M. Alfantazi

Research output: Chapter in Book/Report/Conference proceedingChapterpeer-review

Abstract

Corrosion behavior and degradation mechanism of 625 supperalloy under 47.288 PbSO4 - 12.776 Pb3O5 - 6.844 PbCl - 23.108 ZnO - 10 CdO (wt. %) molten salt mixture and dynamic air atmosphere were studied at 600, 700 and 800 °C. Electrochemical impedance spectroscopy (EIS), open circuit potential measurements and potentiodynamic polarization technique were used to evaluate the degradation mechanisms and characterize the corrosion behavior of the alloy. Morphology, chemical composition and phase structure of the corrosion products and surface layer of the corroded specimens were studied by SEM/EDX and x-ray map analyses. Results confirmed that during the exposure of the alloy to the molten salt, Cr was mainly dissolved through an active oxidation process as CrO3, Cr2O3 and CrNbCO4 while Ni dissolved only as NiO in the system. Formation of a porous and non-protective oxide layer with decreased resistance should be responsible for the weak protective properties of the barrier layer at high temperatures of 700 and 800 °C. There were two types of attack for Inconel 625 alloy including general surface corrosion and pitting. Pitting corrosion occurred due to the breakdown of the initial oxide layer by molten salt dissolution of the oxide or oxide cracking.

Original languageBritish English
Title of host publicationSupplemental Proceedings
Subtitle of host publicationMaterials Fabrication, Properties, Characterization, and Modeling
PublisherJohn Wiley and Sons Inc.
Pages725-734
Number of pages10
Volume2
ISBN (Electronic)9781118062142
ISBN (Print)9781118029466
DOIs
StatePublished - 20 Apr 2011

Keywords

  • 625 Supperalloy
  • EIS
  • Molten Salt
  • Potentiodynamic Polarization

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