Transport by pipe is one the most usual way to carry liquid or gaseous energies from their extraction point until their final field sites. To limit explosion risk or escape, to avoid pollution problems and human risks, it is necessary to assess nocivity of defect promoting fracture. This need to know the mechanical properties of the pipes steels. Hydrogen is considered to day as a new energy vector, and its transport in one of the key problems to extension of its use. Within the European project NATURALHY, it has been proposed to transport a mixture of natural gas and hydrogen. 39 European partners have combined their efforts to assess the effects of hydrogen presence on the existing gas network. Key issues are durability of pipeline material, integrity management, safety aspects, life cycle and socio-economic assessment and end-use. The work described in this paper was performed within the NATURALHY work package on Durability of pipeline material . This study makes it possible to emphasize the hydrogen effect on mechanical properties of several pipe steels as X52, X70 or X100, in fatigue and fracture, and in two different environments: air and hydrogen electrolytic.