Initial Stages of IronChromium Alloys Passivation in Acid Sulfate Solutions

A. N. Podobaev, I. I. Reformatskaya, and E. V. Trofimova

State scientific center of the Russian Federation “Karpov Institute of Physical Chemistry,”
ul. Vorontsovo Pole 10, Moscow, 103064 Russia

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Received May 05, 2005

Abstract—Upon jumpwise applied “maximal critical passivation potential” (that is, the most positive potential at which Fe–Cr alloys still remain in the state of active–passive transition), chromium can continuously accumulate at the surface because of the selective dissolution of iron atoms. This probability can actualize at a chromium content in the alloy of up to 27.7% and pH < 1.2. Oxygen-containing compounds of bivalent chromium are the passivating agents at pH < 1.2 those of trivalent chromium, at pH 1.2.