CHANGE IN THE ELECTRONIC-STRUCTURE OF IRON-CHROMIUM ALLOYS AT CRITICAL CHROMIUM CONCENTRATION

Anode dissolution of iron-chromium alloys in sulfuric acid solution during continuous scraping of the cathode surface in the solution has been studied. The experimental critical concentration of chromium passivation corresponds to the maximum calculated probability that the chromium atom pair is formed in the first coordination shell of a central chromium atom. The abrupt change of the alloy adsorptivity with respect to oxygen and OH ions at the critical chromium concentration is caused by the change in the electronic structure because of the d=electron density transfer from iron to chromium atoms. An attenuation of the electron shielding of iron atoms leads to an increase in Fe-Cr adsorptivity and passivability.