Mechanical behaviour of metallic materials for transport and storage of gaseous hydrogen

Environmental imperatives call for the development of an economy based on the use of low-carbon energies. Among the solutions being studied, the use of hydrogen produced from "green" energy, as an energy carrier or for energy storage, is a fast-growing option worldwide. On a large scale, its transport and storage in gaseous form are among the most economical options.

However, it is known that metallic materials can be rendered "brittle" in the presence of this gas, and this effect can manifest itself in different ways depending on the environment, the material and the mechanical stress. For example, at high temperatures (around 300°C-500°C) and under hydrogen pressure, the formation of methane bubbles at high pressures leads to damage known as HTHA (High Temperature Hydrogen Attack) . On the other hand, at room temperature in aqueous media containing H ₂ S, hydrogen penetrates the metal and recombines to form hydrogen bubbles ("blisters"), which are responsible for decreases in the component's mechanical properties. This phenomenon is known as "HIC" (Hydrogen Induced Cracking) . The preceding examples are associated with conditions encountered mainly in the oil industry. In this article, we will deal specifically with damage observed in the presence of hydrogen gas (typically from atmospheric pressure to 1,000 bar), around ambient temperature, conditions associated with the use of hydrogen for the development of low-carbon energies. This is known as "hydrogen embrittlement" (HE), and is generally characterized by a drop in ductility, a fall in toughness or an acceleration in the rate of fatigue crack propagation. Even under these restricted conditions, various embrittlement mechanisms can be activated.

The mechanical dimensioning of a large-scale hydrogen infrastructure, involving transmission and distribution networks but also the storage of large quantities of gas, requires precise quantification of decreases in mechanical properties as well as a better understanding of the degradation mechanisms involved. Indeed, while several thousand km of H ₂ pipelines have existed for many years in the USA and northern Europe (BeNeLux and France), these networks were...