S. Asakura

Kinetics of Anodic Processes on Iron in Alkaline Solutions

Anodic transients of iron in 1N solution have been investigated. After the electrode was maintained at a potential until steady state was achieved, either an anodic potential step or a potential sweep were imposed. For a potential step, the current transient followed the relations and where is the time after the imposition of the potential step. For a potential sweep of sweep rate, λ, a peak current was observed where For the current transients for both potential step and potential sweep polarization were interpreted in terms of the logarithmic growth of an oxide. For , a duplex structure of the oxide layer, mixed oxide/solution, was assumed, where the mixed oxide consisted of Fe(II) and Fe(III) oxy compounds. The current transient behavior was attributed to composition changes in the mixed oxide layer due to diffusion of Fe(II). The experimental results can be satisfactorily interpreted by assuming the existence of the complex ions, , in the oxide film.

Electrodissolution of Zinc in Acidic Chloride Solutions

Abstract The anodic dissolution of zinc in 1N KCl (pH=3) has been investigated. A potential pulse technique has been used to correct the anodic polarization for the ohmic potential drop. The corrected anodic polarization and the current follow a Tafel relation with a slope of 33 mV/decade up to 200 mA/cm2. The concentration of zinc ions at the zinc/solution interface during anodic polarization was determined by applying long duration cathodic potential pulses. The total charge accumulated is proportional to the anodic current when the current density is small, whereas at high current densities, it attains a constant value. The results at low anodic currents are interpreted in terms of diffusion layer concepts. This interpretation can also be extended to the case when migration effects are significant.