Inhibitor protection of low carbon steel in the flow of sulfuric acid solution containing iron(III) sulfate

Corrosion of low-carbon steel in the flow of H2SO4 solutions containing Fe2(SO4)3, including media with additives of corrosion inhibitors, viz. catamine AB (a mixture of quaternary ammonium salts) and IFKhAN-92 (3-substituted derivative of 1,2,3-triazole) is studied. In the discussed medium, partial reactions of anodic ionization of iron, cathodic reduction of H+ and Fe(III) cations are realized on steel. The first two reactions are characterized by kinetic control, and the latter is characterized by diffusion control. The accelerating effect of Fe2(SO4)3 on the corrosion of steel in H2SO4 solution is mainly due to the reduction of Fe(III). In contrast, in an inhibited acid, the accelerating effect of Fe(III) cations affects all partial reactions of steel. The data on corrosion of low-carbon steel in the flow of the studied media obtained by mass loss of metal samples are in satisfactory agreement with the results of the study of partial electrode reactions. The accelerating effect of Fe2(SO4)3 on steel corrosion in the flow of H2SO4 solutions, including in the presence of inhibitors, is noted. In these media, steel corrosion is determined by the convective factor, which is characteristic of diffusion-controlled processes. Unlike catamine AB, the IFKhAN-92 inhibitor ensures a significant slowdown of steel corrosion in the flow of H2SO4 solution containing Fe2(SO4)3. The reason of higher inhibitor effects of IFKhAN-92 at protection of steel in the considered media as compared to catamine AB is that it slows down partial electrode reactions of metal more substantially.