Material selection for high-pressure valves in hydrogen stations

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When selecting materials for pressure valves, it is essential to consider resistance to hydrogen embrittlement, high-pressure tolerance, corrosion resistance, and sealing reliability, in order to ensure safe and stable operation in high-pressure hydrogen environments. The key material selection criteria are as follows: 1. Main material – 316L stainless steel: It is the most widely used material, offering excellent resistance to hydrogen embrittlement and corrosion; it is suitable for hydrogen systems with a pressure of ≤35 MPa. Its low carbon content and high nickel-chromium composition effectively suppress hydrogen-induced cracking, making it the preferred choice for medium and high-pressure hydrogen valves. Inconel alloys (such as Inconel 625, 718): Used in ultra-high pressure applications (such as 70 MPa hydrogen refueling stations); they possess excellent resistance to hydrogen embrittlement, fatigue, and high-temperature conditions, enabling them to withstand extreme operating conditions. Titanium alloy: lightweight and corrosion-resistant, suitable for high-pressure systems around 45 MPa; it has excellent impact resistance and is often used in valves for hydrogen storage tanks in vehicles. Aluminum alloys (such as 6061T6): Used in specific components (such as bottle valves); they have a low density and moderate strength, but require a design to prevent hydrogen permeation, and are commonly found in 70 MPa hydrogen storage systems. 2. Sealing material: Soft seal – made of polytetrafluoroethylene (PTFE) or reinforced PTFE; suitable for medium and low pressure applications, offering good sealing performance and low friction. Metal hard seal: Uses nickel-based alloys (such as Inconel 625) or tungsten carbide, offering resistance to high temperatures and pressures as well as strong resistance to hydrogen permeation; suitable for conditions of 70 MPa and above. Perfluoroether rubber: Used in components such as pressure relief valves; it resists hydrogen swelling and has a wide temperature range (-20~260°C), ensuring long-term sealing reliability. 3. Criteria and standards for material selection: Matching the pressure rating – 316L stainless steel is used for pressures of 10–35 MPa ； For 35–70 MPa, Inconel alloys or titanium alloys are preferred. Requirements for resistance to hydrogen embrittlement: The material must pass tests in accordance with standards such as ISO11114-3, showing no cracks under high-pressure hydrogen conditions over an extended period of time. Surface treatment: Electro-polishing of the inner wall reduces the risk of hydrogen penetration, improves surface smoothness, and prevents the accumulation of impurities. Connections and gaskets: For flange connections, PTFE gaskets with a Shore hardness of 55–65 are recommended to ensure sealing. 4. Practical application scenarios: Hydrogen refueling stations generally use 316L stainless steel cartridge ball valves (PN42.0MPa), combined with a metal hard-seal mechanism, to ensure the safety of hydrogen filling. Fuel cell system: Uses 316L stainless steel stop valves or solenoid valves, enabling precise flow control and remote automated operation. Storage and transportation of green hydrogen: High-pressure shut-off valves must feature a leak-free design; some products have achieved a 18-month leak-free record, which is promoting the use of domestic alternatives.