Substrate Protection with Corrosion Scales: Can We Depend on Iron Carbonate?

Abstract

Controlling corrosion with naturally occurring corrosion scales is potentially a more environmentally sustainable alternative to current approaches, including dosing of organic corrosion inhibitors. We report operando grazing incidence X-ray diffractograms correlated with electrochemical measurements to elucidate the growth and corrosion protection properties of a corrosion scale composed of FeCO 3 crystallites, which is encountered in various key energy industry applications. Data, acquired as a function of time from high-purity iron immersed in CO 2 -saturated deionized H 2 O at pH 6.8 and T = 80 °C, show that the FeCO 3 scale not only prevents corrosion of the covered substrate but also acts as a significant interfacial diffusion barrier for corrosion reagents and/or products once sufficient coverage is achieved. Most notably, from a corrosion engineering perspective, however, it is determined that corrosion occurring in gaps between scale crystallites remains appreciable; this important insight is gained through the analysis of electrochemical impedance spectra to estimate the variation in electrochemically active surface area as scale coverage increases. These results indicate that naturally occurring FeCO 3 scales are not a tenable solution for corrosion protection, as even in their intact state they are highly likely to be, at best, semiprotective.

Electrochemical behavior of X70 and X80 pipeline steels in a simulated soil environment with and without the presence of chlorides

“…The Akageneite phase, by virtue of its porous crystal structure, tends to reduce the protective ability of the rust layer [27], and this is evident from the low α/γ* values as well as the low Rp values (Figure 17). It has been argued in prior research work that siderite phase fractions in the case of carbonate-bicarbonate solutions, are semi-protective in nature and generally impede the corrosion of the substrate by blocking the gaps between the rust crystallites [29]. However, even with a higher siderite fraction, the protective ability in terms of α/γ* ratio as well as Rp value (Figure 17) are found to be lower than those without chloride content.…”

“…However, a mechanistic understanding of the simultaneous impact of chlorides, as well as solution pH on the passive film behavior, has not been explored. Moreover, the constituents of the rust phases have a critical role to play in imparting protection against further corrosion of the base steel [27][28][29]. Limited literature exists that highlight the role of the chlorides and solution pH on the constituents of the rust phase and its subsequent impact on the protectiveness of the passive film.…”

Satisfactory Tensile Strength and Strain of Recyclable Polyurethane with a Trimaleimide Structure for Thermal Self-Healing and Anticorrosive Coatings

“…Corrosion is a kind of natural reaction that brings about serious deteriorations of metal materials used for industrial infrastructures, such as thermal power plants, bridges, automobiles, railways, etc. − Although polymer coatings are effective to prevent corrosion by limiting the interactions between metallic substrates and aggressive media, the service lives of the anticorrosive coatings are readily shortened by the external mechanical and chemical damages during applications. − Especially, the formation and propagation of cracks in coatings result in significant reduction in their mechanical performances and anticorrosion abilities. − In this regard, developing self-healing coatings that can quickly repair cracks is necessary.…”

Contrast Inversion of Ferrite and Pearlite in a Sweet Corrosion Environment

“…Here we aim to determine the role of microstructural phase constituents when the process is visualised in-situ and in real time. Insitu work [19][20][21][22][23] in this space has included the evolution of X-Ray scattering from a corroding surface, and corresponding electrochemical behaviour averaged over several microstructural domains. This work reported the nature of the scale precursor formed (amorphous or crystalline) [19], and their transformation into crystalline mineral phases and growth with time [20][21][22][23] was addressed.…”

“…Insitu work [19][20][21][22][23] in this space has included the evolution of X-Ray scattering from a corroding surface, and corresponding electrochemical behaviour averaged over several microstructural domains. This work reported the nature of the scale precursor formed (amorphous or crystalline) [19], and their transformation into crystalline mineral phases and growth with time [20][21][22][23] was addressed. Variation due to microstructural heterogeneity could not be considered.…”