The potentiodynamic behaviour of iron in alkaline solutions

Abstract

The potentiodynamic behaviour of iron in alkaline solutions under carefully controlled perturbation conditions reveals that the overall electrochemical process is more involved than was thought earlier. The electrochemical characteristics of the systems are explained through a series of successive conjugated redox coupks principally involving Fe(&), Fe(OH), gnd FeOOH as limiting stoichiometric species. The yield of soluble species such as either FeO:-or HFeO; increases with the pH. Ageing effects of reactants and products are also distinguished through the potentiodyoamic E/I records.

Anodic oxide films of nickel in alkaline electrolyte

“…The oxidation to higher valency oxides proceeds either gradually [2] with "conjugate redox couples" [3,13] or via different stages from NiO to Ni,O, and to Ni,O, [ 10,l 1,14,15].…”

Role of Halides on the Passivation of Iron in Alkaline Buffer Solutions

“…1 to 5 and Table 1. Oxidation and reduction processes occurring on an iron electrode in alkali solutions were reviewed and reported [16,17]. The first anodic peak in cyclic voltammograms is specially due to Fe(OH) 2 formation, the second anodic peak to Fe(OH) 2 with three dimensional oxide films, and the third peak to FeOOH formation [17,18] …”

“…Several mechanisms have been suggested [3][4][5][6][7][8][9] [4,5,14]. Under potentiodynamic conditions, the first anodic peak is specifically related to Fe(OH) 2 formation and the second peak to Fe(OH) 2 with three dimensional oxide film, and the third peak to FeOOH formation [15][16][17][18]. From the variation of the peak height as a function of sweep rate and hydroxide concentration [19], the film growth on the surface was assigned to low field migration of ions through an oxide/hydroxide lattice.…”

Effect of Hot Mill Scale on Hydrogen Embrittlement of High Strength Steels for Pre-Stressed Concrete Structures

“…Once the passivation of the specimen intervenes, the cathodic reduction of oxygen on as received specimens occurs at a potential lower than the values observed on pickled specimens, confirming the electrocatalytic effect of the calamine. With respect to literature data [28][29][30], the peak of the Fe/Fe(II) reaction is not present on the cyclic voltammetric curve, for all the surface conditions of the specimens. This could be due to the presence of the hot-formed oxide on the specimens, but it also shows how pickling cannot restore an iron surface completely absent from oxides.…”