The need for structural materials that can resist hydrogen assisted degradation becomes critical for the continuation of the development of the hydrogen economy. A new neutron reflectivity (NR) approach is exploited to characterise crystallographic changes due to the presence of hydrogen in Al/Al2O3-coated Duplex steel. The degree of hydration after exposure to high pressure hydrogen will be obtained for each layer component. Also hydrogen-induced macroscopic film swelling as well as the increase in crystal lattice plane distances of the films will be determined by NR in order to obtain new measures for the assessment of quality of hydrogen permeation barriers.