Modeling Corrosion Reactions of Steel in a Dilute Carbonate Solution

Abstract

This research models the corrosion reactions of a high-strength steel in an aerated, dilute, carbonate solution during a single-cycle voltammetry. Based on a previous study (Eliyan et al. in J Mater Eng Perform 24(6):1-8, 2015) and a literature survey, the corrosion reactions of the cathodic reduction, anodic dissolution, and passivation, as well as the interfacial interactions and the chemistry of the corrosion products are illustrated in schematics. The paper provides a visual guide on the corrosion reactions for steel in carbonate solutions based on the available mechanistic details that were reported and are still being investigated in literature.

Effect of bicarbonate concentration on corrosion of high strength steel

“…5,9,14 The cathodic reduction becomes less significant, but it continued, with a different mechanism, by the reduction of bicarbonate that generates carbonate and adsorbed hydrogen atoms, depending on the local pH and other miscellaneous factors associated with the course of the ongoing electrochemical and transport reactions. 11 The surface became under total anodic control, during which part of it continued to dissolve, and another to passivate with opposite kinetics, 26 at −0·85 V(SCE), regardless of the increased cycling. With the increased potentials, the currents increased steeply to correspond to an accelerated dissolution process, continuing to generate hydroxyl based and carbon carrying intermediates that saturate the interface and interact at it to adsorb and form first the hydrated Fe(OH) 2 clusters.…”

“…They represent both the continuous reactivity of FeCO 3 (noting the rising currents between the two peaks) forming abundantly by the first peak, and also the reactivity of the underlying substrate, in two processes that lead to the formation of the iron oxides Fe 2 O 3 , with different phases (such as Fe(OH) 3 ), and Fe 3 O 4 , which grow to alter the chemistry of the passive film, at least at its top to be covered with a second layer of a mixture of oxides. 10,11,26 They suppress the underlying dissolution further and by that they resulted in the second peaks with diminishing intensities with increased cycling. The transpassivation currents were as high as 700 mA cm 22 .…”

“…Again, it should be noted that the cathodic currents increased with the bicarbonate concentration, catalysed by the bicarbonate reduction or at least associated to the morphology of the passive film, onto which the reduction sustains possibly in a different mechanism, during which the passive film could partially dissolve. 26 …”

“…7,14,[23][24][25] The iron oxides could form from the earlier stages of the dissolution directly from the surface. 24,26 Transpassivation together with oxygen generation occur at high potentials, during which part of the passive film might chemically transform or dissolve. Upon reversing the voltammetric cycle, the passivation reactions appreciably occur in reverse (in the reduction direction) and, as the potentials become lower, the reduction of the aqueous electroactive species starts to occur, at increasing rates.…”

Determining the Metal Corrosion Rate by Various Techniques and Comparison of the Results

“…In scientific literature, the weight loss is widely used to calculate the corrosion rate ρ (g/m 2 ·h) [1][2][3][4][5][6]. This technique is the reference one.…”