AbstractIn the present work, the hydrogen diffusion during cyclic stress testing in the ferritic chromium steel 1.4521 (X2CrMoTi18‐2) is investigated. Therefore, electrochemical hydrogen permeation measurements are carried out on a hollow cylinder geometry. Simultaneously an alternating stress is applied using a stress ratio of R=‐1. At low stress amplitudes, no influence on the diffusion behaviour of hydrogen is found. At a higher stress amplitude, close to the macroscopic yield strength, a delayed hydrogen permeation by a factor of two is observed. It is postulated that this observation is a result of the nucleation of new hydrogen traps during the measurement. Hydrogen content measurements using carrier gas hot extraction support this hypothesis.