ChemInform Abstract: EFFECT OF HYDROGEN ABSORPTION AND HALIDE IONS ON ANODIC DISSOLUTION OF NICKEL IN SULFURIC ACID

Abstract

Die Versuche werden an geglühten (600°C, 2 h) und verformten ( e = 40‐70%) Ni‐Proben durchgeführt.

The Effect of Adsorbed Atomic Hydrogen on the Electrochemical Dissolution Kinetics of Iron

“…As was noted [1][2][3] , the adsorbed hydrogen strongly affects the dissolution kinetics of iron, which contributes to anomalous anodic behavior of the metal upon its preliminary cathodic polarization, including the change in the slope of the anodic polarization curves, the current hysteresis at a potential scan in opposite directions, and so on. Ideas about the effect of hydrogen on the dissolution kinetics of iron are usually qualitative because of the absence of reliable data on the amount of adsorbed hydrogen.…”

“…The i a -θ dependence in a range of 0.015< θ < 0.036 at a potential (E) of -0.25 V (s.h.e.) is given by log i a = -91.37 θ+ 3.05 [1] In a range of 0.023 < θ < 0.048 at E = -0.3 V, this dependence is given by log i a = -39.0 θ + 1.27 [2] The empirical equations of the kind i = i 0 exp(-Ùθ) were used to describe the cathodic evolution rate of hydrogen or the deposition of metal depending on the electrode surface coverage 6 . Then, it is natural to suppose that Ù constant characterizes the adsorption energy of hydrogen atoms on the electrode.…”

“…Using the θ-τ dependence and Eq. [1], we can estimate the anodic current change with time after the potential jump. At a decrease in θ from 0.0234 (τ = 0) to 0.0167 (τ = 10 s), the current should increase from 8.1 to 33 A/m 2 , i.e., by a factor of 4.…”

“…Using Eqs. [1] and [2] and the estimated i a change depending on τ, we can evaluate the Tafel slopes of the steady-state anodic curve (=43 mV), the polarization curve at a constant θ (=90 mV) and the E-logi I dependence (=63 mV). This result satisfactorily agrees with the experimental data.…”

The Effect of Absorbed Hydrogen on the Iron Dissolution

“…The iron ionization rate depends on the cathodic hydrogen evolution, and the reason for it may be the influence the sorbed hydrogen exerts on the iron dissolution process [1][2][3] . As was noted 4,5 , the adsorbed and absorbed hydrogen forms differently affect the process of the metal transition into electrolyte.…”