Abstract
The transpassive dissolution of Fe-12%Cr and Fe-25%Cr alloys in
near-anhydrous phosphoric acid/acetic acid mixtures has been studied by
conventional voltammetry and electrochemical impedance spectroscopy.
Both steady-state and transient techniques point to two parallel
pathways for the process involving oxidative dissolution of Cr as Cr(VI)
and isovalent dissolution of Fe most probably mediated by an
electrolyte-originating species. A simplified kinetic model of the
process including only surface kinetic steps has been found to reproduce
successfully both the steady-state and the small-amplitude AC response
of the studied materials. The kinetic parameters of the model are
determined and their relevance regarding the influence of the alloy and
electrolyte composition on the relative importance of the two parallel
pathways is discussed. The experimental data and model calculations
indicate that the effect of acetic acid on the reaction steps related to
dissolution of Fe is more significant.
| Original language | English |
|---|---|
| Pages (from-to) | 154-167 |
| Journal | Journal of Solid State Electrochemistry |
| Volume | 9 |
| Issue number | 3 |
| DOIs | |
| Publication status | Published - 2005 |
| MoE publication type | A1 Journal article-refereed |
Keywords
- iron-chromium alloys
- transpassive dissolution
- surface reactions
- electrochemical impedance spectroscopy
- kinetic model