Thermodynamic model for estimating the composition of passive films and Flade potential on Fe-Cr alloys in aqueous solutions |
| |
Authors: | Yu Ya Andreev I A Safonov A V Doub |
| |
Affiliation: | 1.Moscow Institute of Steel and Alloys,National University of Science and Technology,Moscow,Russia |
| |
Abstract: | A thermodynamic model of a passive film is developed, in which the formation of the film on the surface of an Fe-Cr alloy
in an aqueous solution is considered to be a result of the stable solid-phase chemical and adsorption equilibrium at the alloy-inner
passive film layer interface. In the calculations, the Cr2O3 content in the passive film is determined by both the Gibbs energy change (ΔG < 0) in the chemical oxidation of the alloy components by the water oxygen and the change in the surface Gibbs energy (ΔG
S
> 0) of the alloy. The ΔG
S
change results in the negative adsorption of chromium atoms, which shifts the 3Fe + Cr2O3 ↔ 3FeO + 2Cr equilibrium toward the FeO formation in the passive film. Calculations showed that the enrichment of the passive
film in chromium oxide should sharply increase in a chromium content range of 10–20% in the alloy, which agrees with the known
data of X-ray photoelectron spectroscopy of the passive films. A formula is derived for estimating the Flade potential of
Fe-Cr alloys, which relates the Flade potentials of individual Fe and Cr components to the FeO and Cr2O3 contents in the passive film. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|