When pressure sensors come into contact with hydrogen, this often results in difficulties. Unfortunately, I very often notice in my job our customers have no idea of this prior to use. Bold is the reason they often do not even reveal that their medium contains hydrogen. We only find out when we receive a complaint. But why do we get a complaint? How come 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 effectiveness 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 totally destroyed. Regarding 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 employed, 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 result in 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 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. Therefore the consequences of hydrogen can be lowered substantially by selecting suitable materials.
Note
Further information on our pressure sensors and about hydrogen can be found on the WIKA website. If you are using hydrogen as the medium, your contact will gladly recommend an optimum solution for your application.