Specificity of the mechanism of corrosion of sttel in the flow of acid solurion containing iron (III) salt

The thermodynamic and kinetic aspects of corrosion of low carbon steels in a flow of H2SO4 solution containing Fe(III) sulfate, which occurs through parallel interaction of the metal with acid and Fe(III) salt, are considered. Potentiometric studies of a H2SO4 solution containing Fe(III) and Fe(II) salts showed that Fe(III) cations in these media are bound into complexes with sulfate anions, which reduces their oxidizing properties. Voltammetric studies of the behavior of steel in a flow of H2SO4 solution containing Fe(III) sulfate indicate that its corrosion includes the reaction of anodic ionization of iron, occurring in the kinetic region, and two cathodic partial reactions – the release of hydrogen and the reduction of Fe(III) cations to Fe(II), characterized by kinetic and diffusion control, respectively. The partial reaction of Fe(III) cations reduction, which occurs under diffusion control, determines the sensitivity of the entire corrosion process to the hydrodynamic parameters of the aggressive environment and the concentration of Fe(III) salt in it. A linear dependence of the steel corrosion rate on the square root of the rotation speed of the propeller mixer used to mix the aggressive environment is observed. Weak inhibition of steel destruction by a corrosion inhibitor in H2SO4 solutions containing Fe(III) salt is the result of the accelerating effect of Fe(III) cations on three partial electrode reactions of iron.