The need for structural materials that can resist hydrogen assisted degradation becomes critical for the continuation of the development of the hydrogen economy. Hydrogen concentration in steel for traditional storage tanks can increase up to several 1000 ppm during exposure to a hydrogen environment due to gfas, with embrittlement occurring as a result. Application of hydrogen permeation barrier (HPB) coatings, e.g. aluminium oxide, significantly reduces hydrogen embrittlement and therefore enable usage of low-cost Duplex steel for metal hydride storage tanks. A new neutron reflectivity (NR) approach is exploited to characterise crystallographic changes due to the presence of hydrogen in Al/Al2O3-coated Duplex steel in order to obtain new measures for the assessment of quality of hydrogen permeation barriers.