The Transient Regime of the Anodic Dissolution of a Three-Valent Metal Proceeding in Two Steps under Galvanostatic Conditions

Abstract

The transient regime of the anodic dissolution of a three‐valent metal, proceeding in two steps under galvanostatic conditions, is studied for the particular case when z1=1 , z2=2 and i01>i02 . It has been found in going from low to high current densities that the η−t curve changes its shape, namely: for i>inormaler1 , monotone increasing η toward the steady state; for inormalcr1<i<inormalcr2 , peaked‐fshaped η−t curves; for i>inormalcr2 , monotone increasing η toward the steady state again. Under particular conditions of false[M+]normalo values, the overvoltage peak may disappear for inormalcr1<i<inormalcr2 . At the same time the false[M+ ]normalo−t curves have shapes depending on the i and false[M+ ]0 values. The steady‐state value of the intermediate ion concentration increases with increasing current density, passes through a maximum, and then, for very high values of i , decreases toward zero. The decay curves do not display a peak. An apparent remanent overvoltage is noticed, especially for high values of false[M+ ]0 , when the decrease of false[M+false] toward false[M+]0 is slow in comparison with the decrease of η toward zero.

Dissipation Structure of Electrochemical Hydrodynamic Convection

“…The potential profile is completely different from the one in the opposite current direction, where the diffusion-controlled profile is obtained. 12,14 The interferogram (Figure 6a and b) shows that the fluid remains stationary till the maximum of the potential, and after that, the convective motion starts. When the oscillations disappear, the stationary convection pattern is obtained as Figure 6c.…”

Correlations between the Kinetics of Electrolytic Dissolution and Deposition of Iron

“…The quantitative explanation of the nonsteady-state results is difficult in the case of a consecutive charge transfer mechanism (noncatalyzed charge transfer). Plonski (59)(60)(61) has studied the galvanostatic transients by a mathematical treatment. The theoretical results, obtained by computer calculations for a model system, indicate the appearance of "superpolarization" under certain conditions.…”

Electrochemical mechanism of Cr(iii) reduction for preparing crystalline chromium coatings based on 1-butyl-3-methylimidazolium hydrogen sulfate ionic liquid

“…However, for a one-step reaction, h is only monotonous change with the time. 53 In order to further investigate whether the Cr(III) reduction is a two-step process, chronopotentiometric measurements are carried out in 0.55 M Cr(III)-[BMIM]HSO 4 solutions by stepping the current density from 5.0 Â 10 À3 to 5.6 Â 10 À3 A, which are within the theoretical value ranging between 2.09 Â 10 À4 and 5.80 Â 10 À3 A (Fig. 7a).…”

“…The characteristics of chronopotentiometry about a two-step reaction have been reported by Plonski 53 and its most acknowledged characteristics can be described using the theoretical curves given in Fig. 7a.…”

“…Two limiting cases for this type of metal deposition have been classied by Scharier and Hills as progressive nucleation, where the number of nuclei increases during the whole depositing process, and instantaneous nucleation, where all nuclei are formed immediately aer the potential step. [34][35][36] To conrm the nucleation behaviors, the I versus t transients are converted to dimensionless (I/I max ) 2 versus (t/t max ) curves and compared with the theoretical dimensionless curves developed by Plonski et al 53 for the 3D instantaneous (eqn (4)) and progressive (eqn (5)) nucleation. (5) (Progressive nucleation) where I and t are the current and time, respectively, and I max is the maximum current at time t max .…”