Influence of gaseous hydrogen on corrosion of pipeline steel

The paper discusses the interaction of hydrogen with operated pipe steels under conditions modelling transportation of hydrogen through the existing gas transmission network in Ukraine and the role of molecular hydrogen in the processes of corrosion and hydrogenation of pipe steels taking into account operational factors (stresses, working environment, ageing). The tests have been done on steel X70, widely used in pipelines of the Ukrainian gas transmission network. Gaseous hydrogen was supplied to the tested specimen’s area by means of electrolysis using a couple of platinum electrodes and a power supply. It is established that hydrogen significantly affects the electrochemical processes on steel in a model corrosive medium, which indicate the intensity of internal corrosion and hydrogenation of steel from the inner surface of the pipe. In particular, polarization resistance, as a measure of the corrosion activity of the steel, changes essentially with supplying electrolytically generated hydrogen. An additional mixture of the corrosive environment, modelling turbulence in the pipe, intensifies metal dissolution. Operated steel exhibits a higher corrosion activity under these testing conditions. The obtained results indicate the exceptional importance of evaluating the mechanisms of hydrogen interaction with pipeline steels from the point of the safe operation of the existing pipeline network in the case of transportation of hydrogen or its mixtures with natural gas.