Surface investigations of steels treated under hydrogen salt cavern boundary conditions

Abstract

Large-scale hydrogen storage is a crucial part of the energy transition. The usage of salt caverns has a great potential in this process, but there are open questions regarding the construction’s lifetime which need to be investigated prior to their implementation. In this work, potential construction steels were studied. The conditions in a salt cavern were imitated on laboratory scale with an experimental high-pressure setup. Two steels, J55 and H2-ready X56, were systematically exposed to pressure/temperature cycles, gas (H2 and N2), water and brine. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) techniques were used for the characterisation of the steels’ surface, focussing on corrosion effects and crack formation. For both steels, a significant impact of moisture and salt ions could be shown. However, only for J55, intensification of corrosion and cracking on the surface due to hydrogen gas exposure was found. Pronounced crack formation over the entire surface of J55 was revealed. For X56 significantly less crack formation could be observed. Overall, the results strongly indicate better resistance of X56 than J55 against the conditions in a salt cavern, used for hydrogen storage.