Your question should be stated in terms of your objective. If you are duplicating or expanding on someone's work, you should follow their method. If your question is based on how to quantify the amount of hydrogen needed to embrittle a material then it should be based on an environment that accelerates the effect you are studying by several methods. 1. Vary the stress, 2. change the grain structure if you are using metals. 3. Vary the concentration of the Hydrogen. 4. Use a corrosive gas or liquid. 5. Change the temperature. 6. Adapt the methods utilized by others to generate their result. #6 gives you a contextual reference and allows you to utilize the work of others to be specific in pursuit of your end result by changing specific parameters to refine your results. Lastly if your intent is a material study or a stress study in a hydrogen environment, then consider defining the environment in worst case real world conditions. Get the help you need by crafting your question in terms of a precise objective. Embrittlement and stress crack propagation are complex topics and utilizing existing research is possible so long as the information can either be reduced to general guidance or is exactly presented with common parameters.

Hopefully you will find an answer to your question in the attached paper (Hydrogen embrittlement of steel after globulization of carbides).

In simple terms, the difference between those two conditions is whether or not the environment during testing is allowing the hydrogen to escape from the metal. After removal from a hydrogen environment, most metals will start to lose their hydrogen content, as the hydrogen atoms diffuse out of the material and recombine to escape as hydrogen gas. The rate of this loss depends on the material (particularly characteristics like diffusivity and solubility of hydrogen); a material like a ferritic steel may lose enough hydrogen content within the order of minutes that mechanical tests will no longer show an effect of hydrogen while an austenitic steel may take days to lose enough to no longer show an effect. Testing in a hydrogen environment removes (or at least reduces, depending on pressure) the driving force for the hydrogen to leave the sample.

So, which test conditions you want to use depends on the material being tested and the length of the test. If the hydrogen content loss in on the order of minutes, by the time the sample is removed from the environment, the test is set-up, and then run, it is unlikely that the results will show any effect of hydrogen. If the hydrogen content loss is on the order of days, then shorter tests (tensile, fracture toughness) can probably be run before losing too much hydrogen, but fatigue crack growth rate tests, which can take months, will show a decreasing effect of hydrogen as the test continues.

Dear Mr. Walallawita,

It is very important for what purpose hydrogen charging is needed.

This happens by itself during plastic deformation and destruction of metals due to the dissociation of water vapor, see, for example, publications collected in our project: https://www.researchgate.net/project/Hydrogen-saturation-of-metals-during-destruction

Hydrogen charging in a neutral solution or electrolyte solution can be accompanied by a skin effect, which gives a very large inhomogeneity of the hydrogen concentration. At the same time, its concentration inside the sample does not change. See, for example, our article, there is an overview of the results on different methods of hydrogen charging https://www.researchgate.net/publication/346971441_Impact_of_skin_effect_of_hydrogen_charging_on_the_Choo-Lee_plot_for_cylindrical_samples.

The skin effect has two features:

* the concentration of hydrogen when sample kept in air quickly decreases to the initial one (which was before hydrogen charging), in a vacuum it takes several hours;

* plasticity decreases while the stress-strain diagram does not change up to the yield point.

Saturation of samples with gaseous hydrogen gives a more homogeneous effect, but due to the explosiveness of hydrogen, it is far from always possible to apply it in practice. There are also works that show that for a homogeneous distribution of hydrogen, saturation must take at least a hundred hours at a high hydrogen pressure.

It is necessary to separately investigate to what extent this charge is adequate for the purposes of the experiment.

Gaseous Hydrogenation or Autoclave methods.