Diffusion behavior of hydrogen through thermally sprayed coating of 316L stainless steel

Along with other hydrogen barrier coatings, thermally sprayed coating is one of the potential barriers against hydrogen permeation. In this research, specifications of hydrogen diffusion through thermally sprayed 316L stainless steel coating over structural steel are scrutinized by different methods, including complete and partial charging and discharging tests utilizing Devanathan-Stachurski cells. Besides, various mathematical methods are applied to obtain data about the diffusion coefficient of hydrogen, in addition to the solved and trapped hydrogen contents in the coating. The analyses are supported by means of X-ray diffraction (XRD) and microstructural observations to confirm interpretations of hydrogen permeation behavior across the coating. Because of the specific microstructure of the sprayed coatings and continuous ferritic phases across the coating, which develop short pathways for hydrogen diffusion, the thermal sprayed stainless steel coating exhibits diffusion coefficient near that of ferritic steels. Furthermore, the coating contains significantly more reversible and irreversible trap concentrations than that of ferritic steels comprise.