Yes — brass is compatible with hydrogen. Copper and its alloys — brass, bronze and copper-nickel — are rated compatible with gaseous and liquid hydrogen, and hydrogen embrittlement is mainly a problem of high-strength steels. The one grade to avoid is oxygen-bearing copper (Cu-ETP), which hydrogen embrittles: use an oxygen-free grade instead. For a hydrogen-wetted pressure part, take the pressure class from your system standard and put the alloy, threads, sealing faces and cleanliness on the drawing.
Hydrogen projects are moving from pilot scale to industrial deployment: refuelling stations, electrolysers, blending trials in gas networks. Around every one of these systems sit small turned parts — instrument fittings, sensor bodies, adaptors, cooling-water connections — and material engineers ask the same question: is brass compatible with hydrogen?
The answer is yes, with one exception and a few design rules. This guide covers how the metals behave, which alloy belongs in which position of a hydrogen plant, and the drawing details that decide whether a turned part stays leak-tight. Brassland machines brass, copper and aluminium components to customer drawings.
Which metals are compatible with hydrogen
| Material | Behaviour in hydrogen | What it means for the design |
|---|---|---|
| Brass, bronze, copper-nickel | Compatible with gaseous, liquid and slush hydrogen | Used for valve bodies, fittings and instrument parts; brass is among the recommended valve-body materials for liquid-hydrogen valves |
| Oxygen-free copper | Relatively unaffected by high-pressure hydrogen — tested in hydrogen at 69 MPa | The copper grade to specify for parts in hydrogen or in a reducing atmosphere |
| Oxygen-bearing copper — Cu-ETP (C11000) | Embrittled by hydrogen: its oxide inclusions react with the gas | Do not use where the part sees hydrogen, or is brazed or annealed in a hydrogen-bearing atmosphere |
| 300-series stainless steel (316 preferred) | Recommended for gaseous-hydrogen piping | The usual material for piping and high-pressure lines |
| High-strength and martensitic steels | Susceptible to hydrogen embrittlement — delayed cracking under load | The failure mode that hydrogen codes are written around |
Ratings from NASA NSS 1740.16 (Tables A5.1 and A5.2) and the Sandia National Laboratories technical reference on hydrogen compatibility — both linked below. NASA cancelled NSS 1740.16 in 2005, so it serves as a reference rather than a current requirement.
Why hydrogen embrittlement is mainly a steel problem
Hydrogen embrittlement is the loss of ductility that occurs when atomic hydrogen diffuses into a metal. High-strength and martensitic steels are the classic victims: the damage is delayed, it happens under load, and it is the failure mode that hydrogen codes are written around. Copper behaves differently. The permeability of hydrogen through copper is very low — lower than through austenitic stainless steel — because both the solubility and the diffusivity of hydrogen in copper are low.
The one grade to avoid: oxygen-bearing copper
The clear warning concerns copper, not brass. Standard electrical copper, Cu-ETP (C11000), contains oxygen as copper oxide. Hydrogen reduces that oxide and forms water vapour inside the metal, which opens the grain boundaries — often called hydrogen disease. The process is slow at ambient temperature, because both species have to diffuse, and typically shows up after brazing or annealing in hydrogen-bearing atmospheres. For copper parts that see hydrogen or a reducing atmosphere, specify an oxygen-free grade instead of Cu-ETP.
Pressure rating: set by the design and the system standard
A brass alloy has no hydrogen pressure rating of its own. The pressure a fitting holds results from its design — wall thickness, thread and seal — and the pressure class is set by the standard that governs your system. It is confirmed by the proof and leak tests of your qualification.
- Free-machining brass is qualified on the part. CW614N and CW617N contain lead for chip breaking; for a hydrogen-wetted part in these alloys, the proof and leak test on first articles is the evidence.
- Cyclic loading needs its own test. Fatigue behaviour in hydrogen gas is established on the component, so state the load cycles in your test specification.
- Start from the system standard. ISO/TS 15916 covers the basic safety considerations for hydrogen systems; the code that governs your project sets the material rules and the pressure class.
Where brass parts are used in a hydrogen plant
- Water and cooling circuits of electrolysers and compressors — water service, not hydrogen contact. Lead-free CW724R or dezincification-resistant CW602N are the usual choices; see corrosion & DZR.
- Instrument air and pneumatic control — standard CW617N or CW614N fittings.
- Mechanical, non-wetted parts — spacers, bushes, fasteners and sensor housings outside the gas path.
- Hydrogen-wetted pressure parts — material and pressure class are chosen by the system designer to the governing code. 300-series stainless steel is the usual piping material for gaseous hydrogen; brass is among the recommended valve-body materials for liquid-hydrogen valves.
What to put on the drawing
- Alloy by EN designation (for example CW617N to EN 12164 or EN 12165, or CW724R where lead-free is required) and the temper.
- Pressure class and proof or leak test as required by your system standard — you define it; we machine to the drawing, and the pressure test is carried out by an external laboratory or in your qualification.
- Sealing details: thread standard and class, surface roughness on sealing faces, O-ring groove tolerances. Hydrogen is a small molecule, so the seals and threads deserve as much attention as the alloy.
- Cleanliness: name your cleanliness specification (hydrocarbon and particle limits, packaging) — we degrease and pack to the agreed procedure.
- Documents: EN 10204 3.1 material certificate with the heat analysis, first-article inspection report, and any additional test record your qualification needs. See the EN 10204 guide.
Frequently asked questions
Is brass compatible with hydrogen?
Why is hydrogen embrittlement a concern for fittings?
What should engineers check for hydrogen-service brass?
Sources & references
Last reviewed: 27 September 2026. Brassland machines components to customer drawings; the qualification of a part for hydrogen service follows the system standard and is carried out by the system manufacturer.