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Hydrogen Embrittlement of Sensors (ChatGPT)
Amardip Ghosh #Member Profile
Above specifications are for Setra Pressure Transducer Model AXD H
https://www.setra.com/hubfs/Setra_Product_Data_Sheets/Setra_Model_AXD_Data_Sheet.pdf
Hydrogen Embrittlement is a phenomenon where metals become brittle and crack because hydrogen atoms diffuse into the material. It's most common in high-strength steels and some other metals (like nickel alloys), but in principle, any metal can be vulnerable under certain conditions.
Here’s how it happens:
1.Hydrogen atoms, often generated from corrosion, electrochemical reactions, or even the hydrogen gas itself, penetrate the metal.
2.Inside the metal, these tiny hydrogen atoms can congregate at internal defects (like dislocations, grain boundaries, or voids).
3.Over time or under stress, the metal loses ductility and can crack — sometimes without much warning.
If the sensor's diaphragm or wetted components are made from materials susceptible to hydrogen embrittlement (like certain stainless steels or high-strength alloys), over time the hydrogen exposure can cause:
1.Micro-cracks in the diaphragm
2.Drift in pressure readings (due to mechanical property changes)
3.Complete failure (rupture of the diaphragm or sensor body)
4.Also, hydrogen can permeate through thin metal diaphragms — this can lead to hydrogen collecting inside the sensor cavity, affecting the internal electronics (though this is a slower process).
Real-world outcomes:
1.Sensor calibration may drift over time.
2.Sudden failure (no output or wrong output).
3.Tiny leaks from the sensor body.
Mitigation (what manufacturers often do):
1.Use hydrogen-resistant materials (e.g., Hastelloy, special stainless steel grades, or gold-coated diaphragms).
2.Add protective barriers (like coatings) to prevent hydrogen permeation.
3.Design sensors specifically rated for "hydrogen service".
How hydrogen embrittlement affects pressure sensors like the Setra 206 on hydrogen lines
The Setra Model 206 pressure transducer utilizes 17-4 PH stainless steel for its diaphragm and all wetted components . While this material offers excellent mechanical strength and corrosion resistance, it is not recommended for use with hydrogen due to its susceptibility to hydrogen embrittlement.
17-4 PH stainless steel, being a precipitation-hardened alloy, is particularly vulnerable to this phenomenon, especially under high-pressure hydrogen environments. Over time, exposure can result in:
Micro-cracking of the diaphragm
Drift or failure in pressure readings
Sudden mechanical failure
Potential hydrogen leakage
These risks are especially pertinent in applications involving high-pressure hydrogen, such as fuel cells, electrolyzers, or hydrogen storage systems.
Recommendations for Hydrogen Applications
For applications involving hydrogen, it's advisable to consider pressure transducers specifically designed for such environments. These sensors typically feature:
Alternative materials: Use of Hastelloy, Inconel, or gold-plated diaphragms that offer better resistance to hydrogen embrittlement.
Protective coatings: Application of hydrogen-impermeable coatings to prevent hydrogen diffusion.
Specialized designs: Sensors engineered to withstand the unique challenges posed by hydrogen environments.
For instance, Setra's Model 209H and AXD H are designed for high-purity and corrosive gas applications and may offer better compatibility with hydrogen.