The project aims to obtain a fundamental understanding of the effect of inhibitors in high-pressure gaseous hydrogen on the detrimental interaction of hydrogen with steels. The obtained fundamental understanding will facilitate a renewed sustainable energy system, which depends on transporting and storing hydrogen added gas mixtures in existing or new high-pressure structural systems. Gas impurities added to pressured hydrogen can have an inhibiting effect on hydrogen uptake in the material, mitigating hydrogen embrittlement. First, a reproducible in-situ charging methodology for gaseous hydrogen with or without gas impurities will be developed. Subsequently, a systematic evaluation of the effect of different inhibitors on hydrogen uptake in three different steels, selected based on their straightforward microstructure to yield fundamental comprehension, will be performed and the related inhibition mechanisms will be elucidated by advanced surface characterization. Moreover, the effect of multiple parameters (temperature, hydrogen pressure, inhibitor concentration, surface roughness) on the inhibitor efficiency will be evaluated by melt extraction, which determines the hydrogen uptake capacity. A novel in-situ constant load 4 point bending set-up in gaseous hydrogen environment will be developed in order to quantitatively determine the influence of the most effective inhibitors on the hydrogen embrittlement behavior.