A model is proposed for the description of a highly inhomogeneous distribution of hydrogen within a saturated metal specimen (the so-called skin effect due to hydrogen saturation). The model is based on the micropolar continuum approach and results in a nonuniform stress–strain state of a cylindrical metal specimen due to distributed couples or microrotations. The dependence of the diffusion coefficient on the strain energy is considered in order to model stress-induced diffusion. Accumulation of hydrogen within a thin boundary layer results in a highly nonuniform distribution of hydrogen across the specimen. The mutual influence of the stress–strain state and hydrogen accumulation is taken into account. The estimated thickness of the surface layer containing hydrogen is comparable to the thickness observed in experiments. The predicted average concentration coincides with experimental data.

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Boundary layer influence on the distribution of hydrogen concentrations during hydrogen-induced cracking test of steels /

Within the framework of this paper, we review the development of the problem of hydrogen diagnostics for metals. Metal sample enrichment techniques based on the hydr ogen vacuum extraction method had been used for a long time. The development of industrial control technologies has led to the almost complete replacement of vacuum te chniques with atmospheric ones. As a result, systematic errors have occurred. These errors lead to multiple differences of certified hydrogen concentration values from measured ones for standard samples. In this paper, we analyze reasons for the genesis of systematic errors observed for hydrogen measurements while applying the thermal conductivity cell technique. As a result, we have demonstrated that measurements resulting from sample heating and melting in an inert gas flow depend on the heat capacity of the sample and the surface temperature of the melting pot. This explains multiple errors and even negative values in measurements of low hydrogen concentrations.