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H2 Embrittlement Testing

The following is an overview of various systems from our portfolio with which hydrogen embrittlement in metals can be analyzed.
The numerical sequence roughly corresponds to a price order.

1. Standard measuring cell as an instance for first experiments

Often potentiostats, measuring cells and sometimes even tensile machines are present in the laboratories. A tensile specimen is cathodically polarized in the corrosion measuring cell so that hydrogen is generated. This hydrogen penetrates into the sample (if necessary with the help of thio-urea and temperature).

After a defined time, the specimen is removed from the cell, clamped in a tensile testing machine and mechanically loaded until the specimen breaks. A "normal" sample shows the typical necking at the fracture point, a sample damaged with H2 shows a brittle fracture.

Measuring cell sample

Equipment requirement:
  • Potentiostat / Galvanostat
  • Measuring cell
  • Tensile testing machine
  • Optional: thermostat

Tube Cell for test with a load testing machine

With the use of this cell, the above process can be performed in one. The round tensile specimen is simultaneously tensed and electrochemically polarized.

This can significantly reduce the experiment time.

Equipment requirement:
  • Potentiostat / Galvanostat
  • Tube Cell as measuring cell
  • Load testing machine.

Devanathan Cell heatable / not heatable

A Devanathan cell, often called a double-half cell, allows a sample to be clamped as in a membrane.

On the left side, usually called the loading side, hydrogen is generated electrochemically (possibly also purely chemically by pickling), which rises but also diffuses through the steel. On the right side, usually called the measuring side, the hydrogen-induced current is measured electrochemically.

Such a sample, usually a flat sample, can also be drawn to the point of fracture after polarization in the load testing machine.

Equipment requirement:
  • 1 or 2 Potentiostat(s)/ Galvanostat(s)
  • Devanathan Cell
  • Optional: load testing machine, thermostat

Devanathan Cell heatable / not heatable with tensile sample holder

Devices setup as under 3, but here the tensile specimen is inserted directly into a tensile specimen holder developed by us for Devanathan cells.

The sample is exposed electrochemically to hydrogen permeation and mechanically to tensile stress.

Symbolic representation

Equipment requirement:
  • 1 or 2 Potentiostat(s)/ Galvanostat(s)
  • Devanathan Cell
  • Tensile specimen holder for Devanathan cell
  • Optional: load testing machine, thermostat

Test device for constant load samples exposed to pressurized hydrogen

This compact unit contains three small autoclaves, a high pressure pump (1000bar) and a heater (200 °C).

The samples are mechanically preloaded with a small "constant load" tension device and placed completely into the autoclaves (3 samples at a time). Then the autoclaves are brought to nominal pressure and heated. By this device samples can be loaded from the outside with pressurized hydrogen and with temperature.

After a defined measuring time, the experiment is terminated and the samples are removed from the autoclaves.

If they are not broken, this can be done by clamping them in a load system. The same can be done with 4-point bend specimens.

Equipment requirement:
  • Test stand with autoclaves
  • Heating and control system

Hollow tensile specimen test rig

This equipment consists of a tensile testing machine (tensile and compression), a booster system (1000bar) with valves and control, a vacuum chamber with valves and control and, if necessary, a residual gas analysis.

The hollow-drilled sample is first evacuated and then pressurized with 1000bar hydrogen. The permeation flow path here is from the inside to the outside. The sample is surrounded by a vacuum chamber, the ambient air is evacuated and the user can, for example, perform a residual gas analysis in the vacuum circuit to detect the diffused hydrogen. The vacuum chamber also has a safeguarding effect.

If the sample breaks, the hydrogen contained in the sample and pipeline escapes into the chamber and is exhausted. No hydrogen will be released into the laboratory. Furthermore, there is a heating device for the sample, which causes additional stress to the sample. In addition to the duration of the experiment and the residual gas analysis, the fracture pattern can also provide further information about the progress of the experiment.

Since such a system is already at significantly higher prices, it is also possible here, for instance, to initially supply only the high-pressure part. This enables such projects to be split up and, if necessary, smaller budgets to be used up.

Symbolic representation

Equipment requirement:
  • Load testing machine
  • Booster system (1000bar)
  • Vacuum equipment
  • Safety-related control system.
  • Optional: residual gas analysis

Complete H2 test plant for dynamic load test with elevated pressure and temperature

This test plant offers the possibility of mechanically loading tensile specimens in an autoclave under pressure and temperature. This ensures a wide variety of experiments.

Due to the large quantities of hydrogen 1000 liters and more that can escape here even under moderate test conditions, a comprehensive safety concept with appropriate control is necessary here.

Such a plant has to be approved by the local TÜV before commissioning.

Autoclave of the system

Benötigte Ausstattung:
  • Servo-hydraulic load testing machine
  • Autoclave
  • Protective chamber with venting via roof
  • Distribution cabinet for instruments and valves for gas control and gas measurement
  • Cyrostat
  • Safety-related control system.