PSI - Issue 59

Myroslava Hredil et al. / Procedia Structural Integrity 59 (2024) 151–157 Myroslava Hredil, Oleksandr Tsyrulnyk, Ivan Shtoyko, Olha Zvirko / Structural Integrity Procedia (2024)

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Electrochemical behaviour of iron in acidic aqueous solutions is similar to hydrogen electrode, the following equilibria are established: H 2 ⇄ H 2 ( ads ) ⇄ 2H( ads ) ⇄ 2H + + 2 e – , (2) which depend on hydrogen pressure and activity of hydrogen ions (pH) in the solution. Hydrogen uptake by metal can be described as another equilibrium: H ads ⇄ H abs , (3) which also depends on hydrogen pressure in the system according to (2). Therefore, the saturation of the solution with hydrogen shifts the equilibrium (3) towards hydrogen absorption by steel, i.e., its hydrogenation. In our case of a near-neutral environment, the steel surface is covered with corrosion products, and the process of hydrogen generation at the steel surface is slowed down; however, the regularities are maintained. Supplying the electrolyte with gaseous hydrogen thus facilitates the uptake of atomic hydrogen formed as a result of steel corrosion. Hydrogen, in turn, creates internal stresses in steel up to cracking. Moreover, Li and Cheng (2007) found that hydrogen enhanced anodic dissolution of X70 pipe steel in the near-neutral solution. Therefore, exploring the prospects of hydrogen transportation via the existing gas transmission network, the possible intensification of electrochemical corrosion inside the pipeline, its hydrogenation, and HIC of pipe steel shouldn’t be neglected. Using the pipeline system, which has already operated for a long time, might be concerned with a high risk of failures due to HIC and HE. Implementing hydrogen technologies this way requires further extensive studies to ensure the reliability of the pipeline system and the safety of operators and customers. Conclusions Saturation of the model environment, simulating condensate at the pipe's inner surface, with hydrogen considerably reduces polarization resistance of X70 steel and intensifies its hydrogenation. The polarization resistance drop due to the hydrogen action for the steel X70 operated for 37 years is much more significant than that for the steel in the initial state. Recovery of corrosion resistance after eliminating the hydrogen factor is less significant. A combined action of environment mixing and hydrogen bubbling leads to hydrogen-assisted cracking, and it’s more pronounced for the operated steel. It should be taken into account when assessing the risk of integrity violation of the existing gas pipeline network in the case of transporting hydrogen of its mixtures with natural gas. Acknowledgements The present work was financially supported by the Department of Education and Science of Lviv Regional State Administration, Ukraine (Сontract No. 74 dated June 26, 2023). References Al-Moubaraki, A. H., Obot, I. B., 2021. Top of the line corrosion: causes, mechanisms, and mitigation using corrosion inhibitors. Arabian Journal of Chemistry 14(5), 16 – 27. Andreikiv, O.Y., Hembara, N.Т. , 2022. Modeling of the Influence of Hydrogen on the Deformation of Metals. Materials Science, 57 (6), 774 – 781. Barrera, O., Bombac, D., Chen, Y. Daff, D., Galindo-Nava, E., Gong, P., Haley, D., Horton, R., Katzarov, I., Kermode, J. R., Liverani, C., Stopher, M., Sweeney, F., 2018. Understanding and mitigating hydrogen embrittlement of steels: A review of experimental, modelling and design progress from atomistic to continuum. Journal of Materials Science 53, 6251 – 6290. Campari, A., Ustolin, F., Alvaro, A., Paltrinieri, N., 2023. A review on hydrogen embrittlement and risk-based inspection of hydrogen technologies. International Journal of Hydrogen Energy 48(90), 35316 – 35346. Dmytrakh 1 , I.M., Syrotyuk, A.M. and Leshchak, R.L., 2021. Effect of preliminary hydrogenation – dehydrogenation of low-alloy steel on its ability to absorb electrochemical hydrogen. Materials Science 57, 387 – 396. Dmytrakh 2 , І.М., Syrotyuk, А.М., and Leshchak, R.L., 2021. Specific features of electrochemical hydrogenation of low-alloy pipeline steel in a model solution of ground water. Materials Science 57, P. 276 – 283.