Advanced complementary methods for characterization of the CO₂-induced corrosion scale formation on steels: Synchrotron X-ray diffraction and X-ray computed tomography

CO₂ corrosion of steels has been a serious issue in the oil and gas industry resulting in high operational costs, safety issues, and loss of material. Moreover, CO₂ corrosion in subsurface non-producing oil wells used for carbon capturing and sequestration might cause serious tubular’s failure. This is presently becoming a growing concern since the release of the injected CO₂ and the other contaminations could directly influence the climate change. Therefore, corrosion mitigation is of crucial importance to establish environmentally friendly oil and gas production as well as enhancing the integrity and sustainability of the oil-depleted reservoirs exploited for CO₂ injection and storage.
The complex chemical environment in this industry causes the development of several corrosion products/scales in the surface region of the low-carbon steels as a consequence of electrochemical reactions. Here, it is noted that the dissolution of CO₂ in seawater leads to the formation of carbonic acid, which promotes the kinetics of electrochemical reactions between steel substrates and the aqueous phase resulting in the uniform iron dissolution and ultimately the precipitation of various (crystalline) corrosion products at the surface. Hence, it is both scientifically and technologically important to comprehensively investigate the formation, precipitation, and (potentially) transformation of the corrosion products/scales developed on the surface region of the steel when exposed to CO₂ corrosion using advanced ex-situ (post-mortem) and in-situ (direct monitoring) characterization methods.
In this work, the results of characterization of the corrosion scale obtained by employing ex-situ high-resolution electron microscopy, depth-resolved grazing incidence synchrotron X-ray diffraction, and X-ray (micro-) tomography applied on the so-called “end-product” are presented. In addition to the ex-situ studies, we aim at developing in-situ techniques for an in-depth understanding of the mechanisms responsible for CO₂ corrosion using X-ray computed tomography and synchrotron X-ray diffraction. The current research work also addresses the progress made on in-situ X-ray computed tomography and synchrotron X-ray diffraction combined with electrochemical measurements.