Hydrogen is the smallest element on the periodic table, which can be dissolved in steel during typical steelmaking conditions due to its high solubility in the liquid phase. Hydrogen can be picked-up in many way, for example from the moisture of atmosphere, from additives, wet scrap, flux materials, refractory materials and iron alloys which are not fully dried. Hydrogen tends to localize in the discontinuities inside the steel matrix where it can recombine from atomic to molecular state, creating very strong localised pressures that may exceed the resistance of the steel and may give rise to failure or surface defects. The problems of hydrogen content in steels are related to the formation of flakes, the occurrence of break-outs during in continuous casting and to hydrogen embrittlement. For this reason steelmakers have to control that the hydrogen content below the critical value in steel products.


HELIOS 2 PERMEATION is an innovative laboratory instrument that can measure both permeability and hydrogen diffusion coefficient through metallic steel sheets. HELIOS 2 PERMEATION is suitable for evaluating the effectiveness of barrier coatings for hydrogen flux, which is essential for identifying materials in the new hydrogen economy.

The test is carried out referring to ASTM G148 and ISO 17081 Standards.

The traditional equipment used for this type of experiments is the so-called Devanathan-Stachurski double cell, HELIOS 2 PERMEATION replaces the anodic cell with a probe which contains the hydrogen gas sensor.

HELIOS 2 PERMEATION does not require the passivation preparation of the anodic side of the sample and it can assess also diffusivity and hydrogen flux through the coated samples.

Once acquired, the signal that depends on the hydrogen flux through the examined test sample, is processed by proper mathematical codes (by means of a dedicated panel PC) and hydrogen diffusion parameters are evaluated.

HELIOS 2 PERMEATION is a completely automated instrument!

Letomec offers customized instruments and consultancy to define optimal hydrogen charging conditions (current density, electrochemical solution, re-circulation of the test solution, air circulation, etc.), set-up, which depends on the hydrogen charging side that can be electrochemical or gaseous.

The HELIOS Platform including HELIOS 2 PERMEATION is coverd by the Patent N. EP 2912452 B1.

The instrument can be customized according to the user's need.


HELIOS 3 -SHEETS is an innovative solution to get fast, precise and repeatable measurement of diffusible hydrogen content in metallic sheet samples.

HELIOS 3 -SHEETS can be used:

  • to measure diffusible hydrogen content in metallic sheet samples;
  • as laboratory instrument for R&D applications.

Once acquired, the signal is processed by proper mathematical codes (by means of a dedicated panel PC), in order to return the diffusible hydrogen content.

Letomec offers a customized solution in function of customer sample dimensions.


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HELIOS 4-CORROSION is an innovative instrument useful to perform precise and non-invasive diffusible hydrogen measurements on metallic samples, semi-products and products. It consists of a light weight equipment and is based on a solid-state gas sensor.

HELIOS 4-CORROSION is versatile, it operates with no fixed geometry, moreover, as it is portable, it can perform measurements directly in situ or on production line.

HELIOS IV-CORROSION can be used for:

  • diffusible hydrogen content measurements in components exposed to Sour Environments, as in Oil&Gas Plants;
  • Corrosion Monitoring in Chemical industry;
  • Hydrogen Induced Cracking monitoring;
  • Hydrogen Damage Control (Steel Construction, Nuclear Industry, Welding process, etc.)
  • Laboratory R&D applications.

Once acquired, the signal is processed by proper mathematical codes (by means of a dedicated panel PC), in order to return the hydrogen flux exiting from a surface of the examined component. Of course, a hydrogen concentration gradient is needed to have a good quality measurement.


Letomec offers a customized probe according to the test samples shape and dimensions.