THE INFLUENCE OF ELECTROLYTIC HYDROGENATION CURRENT DENSITY ON THE CONCENTRATION OF DIFFUSIVE ACTIVE HYDROGEN IN S235JR LOW-CARBON STEEL

The hydrogen embrittlement (HE) of metals and alloys is the serious problem for many industrial sectors. Therefore, this phenomenon has been intensively studied for over 100 last years. However, many of its features remain unexplained today, what makes it difficult to use certain materials in the conditions favorable for the HE development. The paper covers one of the poorly explored methodological aspects of the HE study – the issue of control of hydrogen concentration in steel using the electrolytic hydrogenation. The electrolytic hydrogenation is widely used under laboratory conditions for metals saturation with hydrogen. However, the unique dependence of diffusive active hydrogen concentration in steel on the cathodic current density during electrolytic hydrogenation is not established until now. Therefore, the interpretation of mechanical testing results following the hydrogenation is hindered.

Using gas analysis, the authors of this paper studied the changes of diffusive active hydrogen concentration in S235JR low-carbon steel and the degrees of its surface and microstructure damage in a wide range of cathodic current densities (between 20 and 600 mA/cm²) of electrolytic hydrogenation. It is established that the dependence of hydrogen concentration in steel on the current density is much more complex than it was considered before. It is shown that the degree of steel surface damage, represented by blisters, depends on the hydrogen concentration. The authors found the substantial similarity between the dependence of hydrogen concentration in steel on the electrolytic hydrogenation current density and the dependence of hydrogen concentration in hydride forming metals on gas pressure during thermal hydrogenation. The authors suggested the explanation of special aspects of the established dependence taking into account the accumulation of steel microstructure damages.