The hydrogenation of specimens was made by electrochemical method. For this aim a special deoxygenated,
near-neutral pH NS4 solution was chosen, Capelle et al. (2010). At these conditions hydrogen atoms are generated
on the steel surface by the electrochemical reduction of water molecules according to known reactions, Cheng
(2007). Before testing, the specimens were coated by special dielectric insulation and after the circular “windows”
(d=5mm) with open surface of metal were made. This open surface of metal served as work electrode for
electrochemical charging of hydrogen. The location of the “windows” with open surface of metal depends on the
subject of test: base metal, weld metal or heat affected zone, Capelle et al. (2013). The electrolytic hydrogenation of
specimens was made with application of the standard three-electrode electrochemical cell (open surface of metal
(working electrode), auxiliary counter electrode and reference calomel electrode) where the Potentiostat VMP has
been used. For modelling the hydrogen entry conditions in real operating pipelines, where there is the situation of