MAX-Phase Coatings as Hydrogen Permeation Barriers

Gas-driven permeation test: H₂ on the upstream side dissociates, dissolves and diffuses through the wall as atomic H, then recombines and is detected downstream. A dense MAX-phase coating sharply cuts the flux that gets through.

H₂ molecule Dissolved H atom MAX-phase coating Steel / cladding
Through the wall
Downstream flux
PRF —
The permeation reduction factor (PRF) is the ratio of steady-state flux without and with the coating. Hotter walls let more hydrogen through and shorten the time-lag before breakthrough. Values are illustrative.