Towards X-ray-based inspection of corrosion in maritime infrastructure

The vast majority of goods are traded transported globally via ocean shipping. The backbone of global trade is therefore dependent on high-quality infrastructure of both ships and ports. As a result, corrosion of maritime infrastructure is a major challenge with enormous potential economic impact. It is therefore key to understand the different factors contributing to the corrosion process to optimize the design of metal structures, material efficiency and anti-corrosion methods for maritime applications. As sea water is one of the most complex and aggressive corrosive environments, early detection of corrosion is crucial for infrastructure preservation. However, the corrosion is often hidden behind layers of corrosion products and biofouling. Studies show that the biofouling layer might slow down the corrosion process, and it would therefore be beneficial to keep this layer intact, preventing in-situ detection by the established inspection techniques. To this end, we perform a pilot study on the application of X-ray micro tomography for the detection of corrosion on steel test samples (S235-coupons) that were exposed to different aquatic environments (fresh water, brackish water and salt water) for several months. MicroCT will be used to examine the severity of the corrosion in these different environments and will serve as a pilot benchmark for corrosion detection. Since the application of full-rotational CT in an actual nautical setting is infeasible (e.g. for inspecting the hull of ships), this work also explores alternative, limited-sampling techniques using the ASTRA-toolbox to overcome the limitations of full-rotational CT and to set the stage for in-situ solutions for corrosion detection in maritime infrastructure.