Hydrogen Influence on Metals: Hydrogen Embrittlement
With the ongoing advancement of hydrogen technologies, materials testing is faced with new challenges: due to the influence of hydrogen (hydrogen embrittlement) on metallic materials during transport and storage, they must undergo comprehensive testing. Pipelines and tanks are the main method of transportation for gaseous hydrogen. Here, ASME B31.12 plays a central role in materials testing as the leading standard for tests on hydrogen-carrying pipes and pipelines.
- Gaseous hydrogen is compressed (200-700 bar) in hydrogen tanks or hydrogen cylinders prior to transport or for storage purposes. To ensure maximum safety at this pressure level, the mechanical stability of the material must be ensured against hydrogen embrittlement. To meet the safety requirements to the greatest extent possible, the material used must be characterized.
- Pipelines are ideal for transport of large volumes of hydrogen across long distances. The already existing natural gas pipeline—with adaptations—is an efficient solution for the transport of hydrogen. Here, material characterization plays a crucial role in the fulfillment of safety standards in order to optimally use the existing infrastructure for both natural gas and hydrogen. It is also possible to mix hydrogen with natural gas. In the development and adaptation of new infrastructures, it is important to know the strength of the used components in terms of their hydrogen embrittlement properties.
Hydrogen embrittlement and material behavior in a hydrogen environment at high pressure are the core elements regarding quality control and development of new materials.
Standardized methods Testing solutions in compressed hydrogen environment Safety standards Interesting customer projects
What is hydrogen embrittlement?
Hydrogen embrittlement is when hydrogen penetrates metal, by which metal loses its ductility (extensibility, formability) and becomes brittle over time. This leads to premature failure below the yield strength of the metal or the design stress of the respective components. In other words, the material gradually gives way to fatigue.
Depending on the source of the hydrogen, a differentiation is made between two types of hydrogen embrittlement (HE):
- Internal hydrogen embrittlement. Here, hydrogen penetrates the material during the manufacturing process.
- Hydrogen-environment embrittlement (HEE). This involves a process in which hydrogen is absorbed from the environment and promotes material embrittlement.
Test method for determination of the behavior of metals under the influence of hydrogen (hydrogen embrittlement)
Many standardized test methods are used to determine the behavior of metals under hydrogen influence. ZwickRoell offers the right testing solutions for these types of tests:
- The ASTM F519 standard describes a mechanical test method with sustained loading to evaluate the behavior of high-strength metallic materials under the influence of hydrogen (hydrogen embrittlement, plating process)
- The ASTM F1624 standard describes an accelerated test method for determining the susceptibility of high-strength metallic materials to hydrogen-influenced time-delayed failure.
- The ASTM E1681 standard defines a method for determining the threshold stress intensity factor for environment-assisted cracking of metallic materials. This test method is also specified by the ASME B31.12 standard in the context of pipe testing and pipeline testing in a hydrogen environment.
Among other conditions, the following standard tests are carried out in a hydrogen environment:
- Tensile tests: ASTM E8 tensile test on metals (as well as ISO 6892-1)
- Creep tests: ASTM E139 Guidelines for conducting creep, creep-rupture and stress-rupture tests of metallic materials, ISO 204 Uniaxial creep testing in tension, ASTM E1457 Standard test method for measurement of creep crack growth times in metals
- SSRT (slow strain rate testing): ASTM G129, ASTM G142
- Creep fatigue / creep fatigue crack growth: ASTM E2714, ASTM E2760
- Fracture mechanics: ASTM E399 K1C critical stress intensity factor, ASTM E1820, BS8571, ASTM E647 Crack growth rates
- Low cycle fatigue / LCF: ASTM E606
- High cycle fatigue / HCF: DIN 50100, ASTM E466-15, ISO 1099
- Tests such as ISO 9015 – Hardness test on arc welded joints, ISO 22826 – Hardness testing of narrow joints welded by laser and electron beam according to Vickers and Knoop, ISO 2639 – Determination and verification of the depth of carburized and hardened cases
Testing systems and options for the simulation of a compressed hydrogen environment
ZwickRoell offers solutions for accurate determination of the extent to which pipelines and tanks are susceptible to hydrogen induced cracks. The findings and results from tests and investigations are subsequently incorporated in the fracture mechanics-based design approach for the hydrogen transport and storage infrastructure to ensure maximum safety of the structural materials.
Creep testing machines, static universal testing machines and servohydraulic testing systems up to 100 kN are used for these tests. The wide variety of tests includes tensile tests, fatigue tests, and fracture mechanics investigations that are performed at pressures up to 1,000 bar in a hydrogen environment via hydrogen autoclave (up to 400 bar; special versions up to 1,000 bar) or hollow specimen adapter (hollow specimen technology; up to 200 bar), and at temperatures ranging from -85 °C to +150 °C.
Comparison between autoclave technology and the hollow specimen method
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Overview of the safety standards
- GB/T 26466: Stationary Flat Steel Ribbon Wound Vessels for Storage of High Pressure Hydrogen
- GB/T 35544: Fully Wrapped Carbon Fiber Reinforced Cylinders with an Aluminum Liner for Theon-Board Storage of Compressed Hydrogen as Fuel for Land Vehicles
- GB/T 34542: Storage and Transportation Systems for Gaseous Hydrogen - Part 1: General Requirements
- EN 17533: Gaseous Hydrogen - Cylinders and Tubes for Stationary Storage
- EN 17339: Transportable Gas Cylinders - Fully Wrapped Carbon Composite Cylinders and Tubes for Hydrogen
- ISO 19881: Gaseous Hydrogen - Land Vehicle Fuel Containers
- CGA G-5.4-2019 Standard for Hydrogen Piping Systems at User Locations
- CGA G-5.6-2005 Hydrogen Pipeline Systems
- CGA G-5.8-2007 High Pressure Hydrogen Piping Systems at Consumer Locations
- ASME B31.12- 2019 Hydrogen Piping and Pipelines
- ASME STP-PT006-2017 Design Guidelines for Hydrogen Piping and Pipelines
