Transpassive Dissolution of Ni in Acidic Sulfate Media: A Kinetic Model

Abstract

The transpassive dissolution of Ni in acidic sulfate media, including the influence of crystallographic orientation, was investigated. The surface plane had low index values, that is (100), (110), and (111). This study was largely based on the analysis of complex impedance. (100) and (110) specimens showed identical electrochemical behaviors, whereas the (111) specimen showed a current density about 20% lower. A reaction mechanism describing the dissolution of the passive film was proposed. This dissolution step was postulated to be catalytic, in the sense that the passive film transformed into a soluble species by anion was not consumed by the transpassive dissolution itself. Calculated polarization curves as well as electrode impedances at various polarization points were in a good agreement with experimental results.

Some beta-Aminoketone Derivatives as Corrosion Inhibitors for Nickel in Hydrochloric Acid Solution

“…After specified periods, the nickel sheets were taken out, rinsed with bidistilled water, dried and weighed. The inhibition efficiency (%IE) and the degree of surface coverage (θ) are calculated by the following equations: (2) where ∆w and ∆w i are the weight losses in absence and presence of the inhibitor, respectively. The galvanostatic polarization curves were measured using a three compartments pyrex glass cell.…”

“…The degree of surface coverage (θ) which represents the part of metal surface covered by inhibitor molecules was calculated using equation (2). The degree of surface coverage was found to increase with increasing the concentration of inhibitors.…”

“…The corrosion resistance of nickel is due to the formation of a passive film on its surface upon exposure to the corrosive media. Many works were conducted to study the passivation of nickel in acidic solutions [1][2][3][4][5]. However, the obtained results showed that nickel establishes a kind of passivity in acidic solutions in which the corrosion current, in the passive potential range, is somewhat higher than those recorded by other passive metals.…”

Corrosion Inhibition of Nickel in Sulfuric Acid Using Tween Surfactants

“…Nevertheless, nickel could be attacked by acidic media in a considerable rate. Many works were conducted to study the passivation of nickel in different acidic solutions [1][2][3][4][5]. It was reported that the passive film formed on nickel surface in low concentrations of sulfuric acid is NiOOH [3] or NiO and Ni 2 O 3 [4].…”

“…It was reported that the passive film formed on nickel surface in low concentrations of sulfuric acid is NiOOH [3] or NiO and Ni 2 O 3 [4]. On the other hand, β-NiSO 4 .6H 2 O was suggested as the passive compound formed in very high concentrations of sulfuric acid [5]. However, the obtained results showed that nickel establishes a kind of passivity in acidic solutions in which the corrosion current, in the passive potential range, is somewhat higher than those recorded by other passive metals.…”