The specially designed, fully equipped, and computerized devices for the underwater long-term measurements have been used to study the hydrogen permeation rate through the structural steels under natural sea water conditions. By applying constant cathodic potentials, the polarization current and the hydrogen permeation rate were recorded. The temperature and the concentration of S{sup}(-2) ions in sea water were also measured. After the tests, the concentration of residual hydrogen in samples and the chemistry of the membrane surface were analyzed. The obtained permeation data were compared with the S{sup}(-2) content in sea water and with the chemistry and appearance of formed deposits. The effect of SRB on the hydrogen permeation through structural steels is dependent on the site of the sample placing and on the sea water temperature. At a lower water temperature, the low hydrogen absorption was measured due to a lower activity of SRB. The highest hydrogen uptake accompanied by the highest content of S in corrosion and cathodic deposits was observed for membranes situated on the sea bed. The electric field of cathodically protected wall did not affect the hydrogen absorption. The hydrogen uptake recorded under the natural sea conditions can be higher than that measured in the laboratory tests, which should be taken into account while servicing marine constructions, especially embedded ones.
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