Because of increasing demands on hydrogen storage for green energy systems, the applied materials have to withstand severe conditions in terms of hydrogen partial pressure and temperature. The two industrial steel grades L80 and P110 are widely used for pipe line applications and were therefore chosen for this study. To determine the hydrogen uptake and the material performance under a constant load at pressures up to 1000 bar and 200 °C, a new autoclave test bench was established. Hydrogen charging at 1000 bar resulted in hydrogen contents of 1.24 wt.-ppm for L80 and 1.36 wt.-ppm for P110 respectively. Furthermore, the effective diffusion coefficients of both materials were determined as 1.4 · 10 ⁻⁶ cm ²/s for L80 and 1.1 · 10 ⁻⁶ cm ²/s for P110 by performing electrochemical permeation measurements. Based on the effective diffusion coefficients, numerical simulations were applied to calculate diffusion profiles and to examine the critical hydrogen content for embrittlement, which is 1.73 wt.-ppm for L80 and 1.0 wt.-ppm for P110 respectively. Although at 1000 bar higher hydrogen contents during tests have been obtained than critical hydrogen contents, none of the conducted constant load tests failed under a load of 90 % yield strength, not even for steel P110.