Carbon dioxide-induced corrosion of industrial equipment is very common, costly and particularly poses new challenges for Carbon Capture and Storage (CCS) systems. The role of impurities, such as SOx and NOx, which are also present in the stream, can also be important and has been discussed recently (cf. Corrosion Science, vol. 236, August 2024).
A group of researchers from the universities of Cambridge and Manchester, including professor Stuart Clarke and his team in the Institute, have been studying how to reduce the rate of corrosion of industrial pipelines under conditions with very high CO2 concentrations. The work involved detailed investigation of the iron carbonate scale that forms and which coats the steel surfaces. It was hoped that by understanding the very initial stages of scale nucleation and early growth, we may facilitate the formation of a protective scale that separates the steel from the corrosive solution. The nucleation process has a crucial role in determining the final scale morphology and protectiveness.
A new paper recently published in Elsevier’s Corrosion Science presents the results of a series of simultaneous small and wide-angle X-Ray Scattering (SAXS-WAXS) experiments, under the very challenging experimental conditions required to capture the commercial environment. This novel approach has a very high spatial resolution such that the phase and state of the nucleating corrosion scale, as a function of both immersion time and location with respect to the metal/solution interface, could be successfully obtained. These experiments enable us to understand the development and growth of the scale in high CO2 environments such as a CCS pipeline.
The results indicate that a precursor amorphous phase is formed prior to the emergence of a crystalline iron carbonate scale (siderite). This behaviour is similar to other materials in the carbonate family; hence, this work also finds relevance with other natural or synthetic nucleating and transforming systems. For example, solutions arising from Fe, Ca mixtures and then Mg, Ca, Fe mixtures might all be expected to show similar behaviour. Similar transformations are also reported for amorphous titania to crystalline anatase or rutile, or ferrihydrite to goethite or haematite.
You can read the full article here.