Electrogravimetric and coulometric measurements were performed on thin palladium film by means of a quartz crystal microbalance. According to the applied potential, two regions appear: the α-phase and the β-PdH phase. If in the first one microbalance and coulometric measurements gave compatible results in the latter phase large differences were observed. Various hypothesis can explain this dysfunction. On the one hand, the quartz microbalance would not only measure a mass change in the β-PdH phase but a frequency change related to the stress due to the insertion of hydrogen atoms in the palladium lattice as well. Therefore, the Sauerbrey equation would not be valid. On the other hand, the trapping of hydrogen in sites close to the electrode surface would change the rheology of this sublayer, which can change the value of the Sauerbrey coefficient. At least in the α-PdH phase, the model presented in this paper was in good agreement with the experimental results. In addition to the classical mechanism (Volmer, Heyrovski, Tafel reactions) the consideration of a trapping of hydrogen in a sublayer under the electrode surface and a direct desorption of the trapped hydrogen is validated.