The Active Iron Electrode

Abstract

The pH and potential dependencies of the steady‐state iron dissolution and hydrogen evolution reactions were determined for zone‐refined iron in H2‐saturated acidic sulfate solutions. The mechanistic significance of the data is examined in detail. The results of this investigation serve to resolve the conflict concerning the mechanism of iron dissolution in noninhibiting media and to provide an experimental and mechanistic base for the interpretation of the electrochemical behavior of the active iron electrode in inhibiting media.

Studies on Corrosion of Annealed and Aged 18 Ni 250 Grade Maraging Steel in Sulphuric Acid Medium

“…This indicates that the mechanism of corrosion process is different at lower concentration levels and higher concentration levels; and mechanism remaining the same within the concentration ranges mentioned at both the levels. The values of cathodic Tafel slopes at higher concentration ( b c , 120 mV/dec) suggest that the hydrogen evolution reaction (HER) is independent of sulphate ion concentration, the rate determining step in the HER is the discharge reaction, a result which agrees with previous works [17,[28][29].…”

“…This may be due to the change in hydrogen overvoltage, which in turn affects the cathodic polarization curve. This may be also due to the contribution from concentration polarization [17], which leads to deviation of cathodic curve from Tafel behavior at lower cathodic potentials, since the variation in b c is more prominent at lower concentrations of acid. In aged specimen Tafel slopes remain approximately the same.…”

Hydrogen Evolution Reaction on Spheroidal Graphite Cast Iron with Different Graphite Areas in Sulfuric Acid Solutions

“…Many previous studies of hydrogen evolution reaction on pure iron have shown that the Volmer reaction is appropriate as the ratedetermining step. 25,[27][28][29] Thus, hydrogen evolution reactions on pure iron and cast iron are found to be the same.…”

“…This value is two or five orders of magnitude lower than that of pure iron composed of only ferritic matrix. 25 It is inferred that the rate of hydrogen evolution reaction of graphite particles in the cast iron is the same as that of the graphite electrodes. Thus, the cathodic current density of hydrogen evolution reaction on graphite particles Electrochemistry, 82(2), 104-108 (2014) in cast iron matrix is considered to be negligible.…”

Electrochemistry and Corrosion on Homogeneous and Heterogeneous Metal Surfaces

“…(29)], the total current density is given by (cf. Stern(23)) (30) This equation resembles the Butler-Volmer equation for a single reaction, where the corrosion potential and corrosion current density have replaced the equilibrium potential and exchange current density. The primary justification for writing the equation in this form is to describe the corrosion kinetics concisely and economically.…”