This article was originally published on May 31, 2023, and updated on June 11, 2025.
As industries move to adopt hydrogen as a clean energy source, the demand for robust pressure sensing technology has never been greater. But hydrogen introduces unique challenges. For example, many hydrogen applications have processes that can cause hydrogen ion diffusion. This can lead to hydrogen permeation and embrittlement, which can cause premature failure of your measurement instruments.
Ashcroft is a leading authority in pressure and temperature instrumentation, with decades of experience designing solutions that meet the unique demands of hydrogen environments. We wrote this article in response to a question that came into our help desk.
Read on to learn about hydrogen permeation and hydrogen embrittlement, why they matter in hydrogen applications and how several Ashcroft® pressure transducers are uniquely engineered to mitigate each of these issues. You will also find additional resources that may address other questions you may have about hydrogen applications and selecting the right instrumentation for your system.
What is hydrogen permeation?
Hydrogen permeation occurs when high pressure and temperature cause H₂ molecules to separate into hydrogen ions. These ions are small enough to penetrate the thin lattice structure of metal diaphragms, such as those found in many pressure transducers and diaphragm seals.
In instruments that rely on the metal diaphragms to convey system pressure — either directly to a strain gauge or through a fluid-isolated sensor that attaches to a strain gauge — the diaphragm becomes the weak link in the system. Once inside the diaphragm, the ions reform as H₂ molecules in the isolation fluid and form hydrogen bubbles, disrupting the pressure sensor performance and causing zero and span shift errors (or instrument failure) over time.
Figure 1. Hydrogen permeation illustration
Hydrogen is used in many industrial applications and processes, including:
- Petroleum refining – hydrocracking
- Fuel cells
- Hydrogen fueling stations
- Glass manufacturing
- Semiconductor manufacturing
- Aerospace applications
- Fertilizer and ammonia production
- Welding, annealing, and heat-treating metals
- Pharmaceuticals
- Power plant generator cooling
- Hydrogenation of unsaturated fatty acids in vegetable oil
How to prevent hydrogen permeation
When selecting the right instrumentation for your hydrogen applications, the biggest factors include material and design. Here are a few strategies to consider:
1. All-welded instruments with 316L or A286 wetted materials
Transducers that feature all-welded construction and materials with a tight lattice structure, like 316L stainless steel and A286, enhance resistance to hydrogen-induced damage.
2. Gold-plated diaphragms
Using gold-plated 316L stainless steel diaphragms, which are offered on diaphragm seals, provide an ultra-dense lattice that acts as a barrier to hydrogen ions and dramatically increases the diaphragm's resistance to permeation.
3. Application pressure range
In addition to the lattice structure of a material, hydrogen permeation is also influenced by the pressure of an application. The higher the pressure of the application, the larger the force that is applied to the diaphragm. This force stretches the lattice structure of the material, allowing more hydrogen ions to permeate the material.
With this in mind, you should use a material that not only has a tight lattice structure but is also well suited to handle the pressure range of the application.
What is hydrogen embrittlement?
Hydrogen embrittlement occurs when hydrogen atoms infiltrate metal components, reducing their ductility and making them prone to sudden, brittle fractures. This phenomenon, also known as hydrogen-induced cracking or hydrogen attack, can occur in both gaseous and aqueous hydrogen environments.
Like hydrogen permeation, embrittlement is driven by hydrogen’s ability to penetrate metal structures—but in this case, the result isn’t measurement drift, it’s material failure.
Here's how it happens:
Once again, as hydrogen molecules (H₂) diffuse, they create hydrogen ions, which are among the smallest ions in the world and can penetrate microscopic flaws or imperfections on the surface of metals like high-strength steels, titanium alloys, aluminum alloys and electrolytic copper. Once inside the metal, these atoms can recombine into H₂ molecules. As the molecules accumulate, they exert pressure within the material structure.
Over time, this internal stress can lead to cracking, even when the material is exposed to stress levels below its yield strength. The result is a sudden and often catastrophic failure of the metal.
Figure 2. Hydrogen embrittlement illustration
Types of hydrogen embrittlement
In addition to the general definition of hydrogen embrittlement discussed above, NASA crews who work with hydrogen created the HEE Index. This material screening tool evaluates the severity of hydrogen embrittlement effects on certain materials. They also defined a few more types, including:
- Hydrogen Environmental Embrittlement (HEE): The weakening of certain mechanical properties that occurs when a material is subjected to applied stress and intentionally exposed to a gaseous hydrogen environment.
- Internal Hydrogen Embrittlement (IHE): The deterioration of specific mechanical properties that result from the inadvertent introduction of hydrogen into vulnerable metals during forming or finishing processes.
- Hydrogen Reaction Embrittlement (HRE) — The degradation of certain mechanical properties that takes place when hydrogen reacts with the metal matrix to form metallic compounds like metal hydride at relatively low temperatures. This form of hydrogen damage can occur in materials such as titanium, zirconium and even some types of iron or steel-based alloys.
How to prevent hydrogen embrittlement
Similar to hydrogen permeation, when selecting instruments to combat hydrogen embrittlement, material selection and instrument design are critical. However, the risk factors are different.
For instance, while some prevention strategies, like choosing 316L stainless steel or using gold plating, help with permeation and can also reduce embrittlement risk when the material is thin or under minimal stress. For embrittlement, where the primary risk is structural cracking or failure, the focus should be on high mechanical stress, material strength, and prolonged exposure to hydrogen pressure.
Generally speaking, if you want to ensure safe hydrogen applications, use pressure transducers with at least 316L stainless steel. And for pressure ranges 5,000 psi or greater, Ashcroft recommends using A286 diaphragm, which maintains a tight lattice structure at pressures up to 20,000 psi and avoid oil-filled sensors, which can create bubbles and sensor drift.
The Ashcroft® E2F Explosion-Proof Pressure Transducer and the E2S Intrinsically Safe Pressure Transducer feature A286 diaphragms and 316L stainless steel sockets that are approved for hydrogen applications.
Ready to learn more?
Armed with more information about the dangers of hydrogen permeation and embrittlement, you may have more questions about choosing the best instrumentation for your hydrogen system. Here are a few related articles that you may find interesting:
- Advancements in Pressure Sensors for Hydrogen Applications
- What are Safe Temperature Sensors for Hydrogen Applications?
- Choosing Pressure Sensors for Hazardous Locations
- How Much Do Pressure Transducers Cost? (6 Factors Impacting Price)
- How Does Media Temperature Affect Pressure Transducer Performance?
Contact us anytime to speak to an industry expert. In the meantime, download our guide to learn how to avoid hydrogen hazards.
