Investigation of the kinetics of the electrode processes and electrochemical dissolution of iron under conditions of continuous renewal of its surface under the solution

Abstract

1. The electrochemical behavior of iron in electrolytes in the case of continuous renewal of its surface was investigated. The decrease in the overvoltage of the evolution of hydrogen on an iron electrode observed in the case of renewal of the surface is associated with exclusion of the steps associated with the slowness of the removal of adsorbed hydrogen from the surface of the metal from the total value of the overvoltage. 2. The almost complete elimination of the overvoltage of the anodic reaction of ionization of the metal (nonpolarizability of a Fe electrode under conditions of renewal of the surface) is due to the removal of adsorbed anions of the solution from the surface of the Fe electrode, which are the basic inhibiting factors for the occurrence of the anodic process. 3. The inhibiting effect of Br− ions in the concentration interval from 0.01 to 0.5 N, as well as of surface-active additions of tetrabutylammonium, both on the cathodic and on the anodic processes (and consequently on the corrosion rate as well), are reduced to their adsorption on the surface of the iron electrode. 4. In the case of intensive renewal of the surface of iron, the adsorption inhibition of halide ions, as well as organic tetrabutylammonium cations, introduced into H2SO4 solution, can be entirely eliminated. 5. The required rate of renewal of the electrode surface from adsorbed anions (Br−) increases with increasing concentration of the anion in solution, which is due to a concomitant increase in the rate of adsorption of the Br− anion. 6. In the corrosion of iron in acid media, and presumably in other media as well, under conditions of continuous and constant renewal of the surface, a substantial acceleration of electrochemical corrosion should be observed as a result of facilitation of the electrode processes.