When pressure sensors come into contact with hydrogen, this often results in difficulties. Unfortunately, I very often notice in my job that our customers are not aware of this prior to use. This is why they often do not even tell us that their medium contains hydrogen. We only find out when we receive a complaint. But why do we get a complaint? Why is especially hydrogen so critical to pressure sensors?
A basic rule is that a large number of metals become brittle when exposed to hydrogen. Hydrogen atoms that diffuse into the metal grid change the strength of the material. In the worst case, this results in cracks in the material. Or to put it simply, the pressure sensor starts leaking or is completely destroyed. In the case of pressure sensors, in particular thin membranes required for measuring pressure play a decisive role. Atomic hydrogen can not only penetrate the metal, but also pass through it by diffusion.
This has several effects: When piezoresistive measuring principles are used, it becomes critical if hydrogen reacts with the internal transmission medium or accumulates there. This initially only falsifies the measurement results, but can later on also lead to complete destruction of the sensor in individual cases. The addition of hydrogen also changes the instrumentation characteristics of the resistance structures of the measurement bridge of thin-film sensors. Despite being reversible, this process leads to a detuning of the bridge at least temporarily, resulting in a falsification of the measurement signal.
However, the effects described above occur in different materials differently. This means that the effects of hydrogen can be lowered substantially by selecting suitable materials.