The rapid growth of hydrogen infrastructure requires materials capable of withstanding extreme operating conditions, especially in Printed Circuit Heat Exchangers (PCHEs). These units are extensively used for H2 compression in refuelling stations, where design pressures and temperatures can reach up to 1034 bar and 250°C. However, the diffusion welding process used to make them can cause alterations in the microstructure, which may affect the material's susceptibility to hydrogen embrittlement. This study investigates hydrogen penetration in chemically etched and diffusion-welded AISI 316L. A comparative analysis was conducted to evaluate the hydrogen absorption kinetics of the material in two different states: the base metal (before diffusion welding) and the monolithic diffusion-welded block.