When pressure sensors come into contact with hydrogen, this often results in difficulties. Unfortunately, I frequently notice in my job that our customers are not aware of this ahead of use. Critical is why they often do not even tell us that their medium contains hydrogen. We only learn when we get a complaint. But why do we get yourself a complaint? Why is especially hydrogen so critical to pressure sensors?
A simple 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 even to put it simply, the pressure sensor starts leaking or is completely destroyed. In the case of pressure sensors, specifically thin membranes required for measuring pressure play a decisive role. Atomic hydrogen will not only penetrate the metal, but additionally pass through it by diffusion.
It 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 technique results in a detuning of the bridge at least temporarily, resulting in a falsification of the measurement signal.
However, the consequences described above occur in various materials differently. Which means that the effects of hydrogen could be lowered substantially by selecting suitable materials.
Note
Shameless on our pressure sensors and about hydrogen can be found on the WIKA website. If you use hydrogen as the medium, your contact will gladly recommend an optimum solution for the application.