Discovery of a foreign-gas barrier effect for mitigating hydrogen corrosion and its enhancement approach: A multiscale modeling study

Hydrogen corrosion is a critical challenge to H 2 -containing equipment and needs to be well addressed in light of the booming hydrogen-energy industry. Herein, based on the molecular dynamics and density functional theory, we report the discovery of a foreign-gas barrier effect that foreign gases (CH 4 , CO 2 , N 2 or NH 3 ) tend to accumulate near metal (Fe, Cu, Al, Cr, and Ni) surfaces and effectively keep metals and H 2 apart. This effect is magnified at reduced H 2 concentrations and can be instrumental in mitigating hydrogen corrosion if well utilized. To take better advantage of this effect, specific surface coatings (e.g., graphene) are proven useful in boosting it by amplifying affinity differences between metal surfaces and gases. Moreover, based on computational fluid dynamics, it is found that special macroscopic structures, such as novel coaxial flow designs used for H 2 /CH 4 blending pipelines, can enhance this microscopic effect by yielding much lower near-wall H 2 concentrations than conventional T-pipes. This work provides important and enlightening findings for the design and protection of hydrogen-energy equipment. • Distribution of H 2 -containing gases near metal walls is probed on multiple scales. • A foreign-gas barrier effect that can improve hydrogen safety is discovered. • Specific coatings (e.g., graphene) and structural designs can enhance this effect. • A coaxial flow design enhances this effect by diluting H 2 near pipeline walls.