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Electrochemical response of various metals to oxygen gas bubbling in molten LiCl–Li2O melt

  • D. HorvathEmail author
  • O. Dale
  • M. Simpson
Article
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Abstract

The electrochemical response of several alloys (stainless steel 316, Hastelloy C276, Inconel 600, and tantalum) was investigated in molten LiCl–Li2O (1 wt%) at 923 K while bubbling oxygen gas into the molten salt. Tafel and zero resistance ammeter (ZRA) electrochemical methods were used to measure electrochemical effects of oxidation processes at the surface of each alloy. The Tafel method required approximately 15 min and was, thus, applied only in intervals between periods of oxygen bubbling in the salt. ZRA measurements were made in real time, while the O2 was actively being bubbled into the salt. This method recorded both open circuit potential of the alloy relative to a Ni/NiO reference electrode and current between the alloy and the galvanically coupled platinum plate that served as the counter electrode. Both open circuit potential and galvanic oxidation current started to increase at the initiation of oxygen flow. Based on the observed oxidation current trend, it was inferred that the metals in order of increasing resistance to oxidation in molten LiCl–Li2O are as follows: tantalum < SS-316 < Inconel 600 < Haynes C276. Scanning electron microscopy images indicated formation of an oxide layer of thickness 560–3370 nm that correlates with the galvanic oxidation current measurements.

Keywords

Corrosion Molten salts Oxide reduction 

List of symbols

\( a_{\text{ox}} \)

Activity of oxidized species

\( a_{\text{red}} \)

Activity of reduced species

\( \beta_{\text{a}} \)

Anodic Tafel constant (V/decade)

\( \beta_{\text{c}} \)

Cathodic Tafel constant (V/decade)

\( E_{\text{eq}} \)

Equilibrium potential for reaction (V)

\( E^{0} \)

Standard reduction potential (V)

\( E_{\text{corr}} \)

Corrosion potential (V)

\( E_{\text{oc}} \)

Open circuit potential (V)

\( I_{{}} \)

Overall measured current (A)

\( I_{\text{corr}} \)

Corrosion current (A)

n

Moles of electrons

R

Ideal gas constant (J/mol K)

T

Temperature (K)

Notes

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Copyright information

© Akadémiai Kiadó, Budapest, Hungary 2019

Authors and Affiliations

  1. 1.Department of Metallurgical EngineeringUniversity of UtahSalt Lake CityUSA

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