CORROSION-ELECTROCHEMICAL BEHAVIOR OF IRON DISILICIDE IN SULFURIC ACID ELECTROLYTE

The corrosion-electrochemical behavior of FeSi2 electrode in 5% H2SO4 and 5% H2SO4 + (0.1–0.5) g/l NaF solutions was studied. It is concluded that in 5% H2SO4 solution with a corrosion potential, an oxide film is formed on the FeSi2 surface, which is similar in composition to SiO2. The oxide film is not reduced at low cathodic polarizations; as a result of anodic polarization, the film grows and is doped with iron oxides. The presence of an oxide film on the silicide surface determines its high chemical resistance. It is shown that the effect of sodium fluoride, which activates the dissolution of FeSi2 electrode in a sulfuric acid solution, is associated with a weakening of the passivating effect of silicon dioxide and iron oxides. With increasing of NaF concentration, the role of iron in the kinetics of electrode processes on silicide increases, while that of silicon decreases. The order of the reaction of FeSi2 dissolution by NaF was calculated depending on the potential.