MATERIALS TESTING IN GASEOUS HYDROGEN ENVIRONMENT

In case of high-pressure hydrogen application, the hydrogen embrittlement risk assessment should be carried out in  gaseous environment. Dedicated facilities to reach high-pressure and/or high-temperature are needed, in Letomec a series of tests are now available but testing services are constantly increased.

Typical hydrogen purity is 6.0.

Gaseous Hydrogen Permeation Tests

Gaseous permeations should be performed in the case of                                                                                  gaseous hydrogen applications, for the evaluation of                                                                                   effective hydrogen diffusivity in steels.

Tests can be carried out on bare and coated steels with general reference to ISO 17081 and ASTM G148. Limit conditions are T = RT ÷ 500 °C, P = 1 bar.

Test consists in exposing one side of a metal plate to gaseous hydrogen environment and put the other side is in contact with the HELIOS reading probe, able to measure the hydrogen flux permeating through the metal.

Moreover, it is also possible to perform permeation tests on a portion of real pipe filled with operative gas mixture at laboratory scale or directly on field!

Solubility and trapping investigation

In order to characterize hydrogen solubility in a metal, it is possible to perform a series of hydrogen measurements on coupons exposed to hydrogen gaseous environment.

Elaborating the results of hydrogen measurements, the constants of Sievert’s law can be estimated. Typical expousure conditions are T = RT ÷ 500 °C, P = 1 ÷ 200 bar.

Moreover, it is possible to estimate the effective hydrogen diffusion coefficient by indirect method based on Hot Gas Extraction.

Mechanical tests

Norms currently applied in energy sector suggest a series of mechanical tests including fracture mechanics and fatigue to correctly characterize new materials for gaseous hydrogen application. Static or quasi-static load tests can be useful to determine the durability, while fracture mechanics and fatigue tests can be useful to characterize the behaviour in presence of cracks with static or cyclic loads respectively.

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