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14–16 Oct 2025
Institute of Nuclear Physics
Asia/Tashkent timezone

Structural state of the material of the container, long-used for hydrogen storage.

Not scheduled
20m
Institute of Nuclear Physics

Institute of Nuclear Physics

Ulugbek town, Tashkent, 100214, Uzbekistan
Poster

Speaker

Ms Tamara Aldabergenova (Tamara)

Description

Recently, hydrogen has become an increasingly important energy source in line with the global trend toward de-carbonization of the economy. The issue of storage and transportation of hydrogen fuel to the end user arises as hydrogen consumption increases. Further development of hydrogen transportation technologies faces a number of challenges related to hydrogen-induced degradation of the structure and mechanical properties of storage tank materials caused by hydrogen.
Metal (steel and cast iron) cylinders of high pressure (up to 200 Pa) are used as hydrogen storage tanks. Since the beginning of the era of application of such cylinders, high strength has been one of the main requirements to the materials for their manufacture. There were no special requirements for the steel grade and its structural-phase state. The range of material properties required has expanded as manufacturing and application experience evolved. Obviously it is necessary to reduce hydrogen degradation of the material, to reduce the total weight of containers, and for this purpose light alloys, polymers and other materials are used. However, successful experience of use, established production and a large number of available finished products demonstrate the applicability of metal cylinders. Of particular interest are materials that have completed their design life and have been taken out of service. The study of such materials allows to estimate the degree of damage and the remaining service life of the containers. The analysis of the obtained data will help to estimate about the response of the materials under hydrogen storage conditions.
The subject of the study was the wall of a high-pressure container for the storage and transportation of gaseous hydrogen. The container was commissioned in 1937 and decommissioned in 1972. Thus, the service life was to 35 years, after which the container was determined for long-term storage in a mothballed state; the storage period was up to 50 years. The mothballed state implies the presence of residual hydrogen pressure in the container.
The material has been certified: elemental, phase and microstructural analysis. The elemental composition is as follows (by wt. %): C - 0.14 %, Al - 0.5 %, W - 0.35 %, Mn - 0.32 %, Cr - 0.26 %, Si - 0.14%, Cu - 0.13 %, Ni - 0.1%. The material is defined as an iron-carbon alloy in the form of a eutectic mixture of ferrite-cement with a ferrite-pearlite structure with a large number of large defects. The differences in shape and geometric dimensions of the structural elements were evaluated according to the thickness of the container walls. The wall thickness is 8 mm. Also, the difference of the structure parameters is determined in different projections.
The container wall material has a heterogeneous structure after long-term use for hydrogen storage. Near the inner surface, the crystal structure is more distant than the base material. Also near the inner surface there are microcracks and less carbon-containing phase (pearlite). Further down, there are a large number of large carbon-containing defects. Their number and size decrease toward the outer surface. These defects are likely to contain hydrogen combined with carbon. The appearance of such defects is often associated with the interaction of hydrogen with carbon, which is part of the pearlite phase, and is accompanied by the destruction of this phase.
In thermodesorption tests (TDS), the temperature dependence of the parameter Dn/dt - the growth of the partial pressure was evaluated in the working chamber in conditional units, which characterizes the rate of escape of gas particles from the sample. The experiment was repeated for samples cut directly under the oxide layer on the inner surface of the cylinder wall and at a distance of 2 and 4 mm from the surface. It is found that hydrogen escapes during heating both in the free state (H2) and in the states of carbon and oxygen.
Hydrogen in the material is mainly in the bound state and is located in three main types of irreversible traps. Regardless of the type of trap, the release of pure H2 is minimal. In general, the maximum hydrogen concentration is observed in the near-surface layer up to 1 mm thick.

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