Material integrity refers to the ability of materials to retain their properties and perform well throughout their lifespan in infrastructures, such as in plants and components. Selecting the right materials and ensuring their performance in the hydrogen value chain is crucial for safe and efficient use of both hydrogen and ammonia. Similar to hydrogen, ammonia (NH3) is an energy carrier. However, it must be decomposed to produce hydrogen, which can then be used as 'fuel'.
FME HYDROGENi has conducted a study where they have mapped which materials are in contact with hydrogen and ammonia in the hydrogen value chain. The study is a collaborative effort by the four research areas in FME HYDROGENi, aimed at gathering essential information on material systems, applications, environmental conditions, and integrity challenges in the hydrogen value chain. It is partly based on a digital survey and interviews conducted with industry partners.
Hydrogen has potential to cause hydrogen embrittlement and corrosion in metals, as well as degradation of polymers. While hydrogen is absorbed and transported as atoms in metals, it is present as hydrogen molecules in polymers. Polymers can typically suffer from impaired mechanical properties caused by swelling from hydrogen ingress, and failure due to sudden decompression of high-pressure hydrogen.
– We need to ensure that structural metallic materials in the hydrogen value chain, like carbon manganese steels, stainless steels and nickel alloys have sufficient resistance to hydrogen embrittlement, because it will reduce ductility and impair fracture and fatigue properties, says Vigdis Olden, Senior Research Scientist at SINTEF.
Ammonia is inherently corrosive to some metallic materials, and the main challenge here is stress corrosion cracking.
Materials in production and transport of hydrogen
The study shows that increased lifetime of components in electrochemical cells and stacks for hydrogen production is on the industry partners wish list. One challenge here is how to avoid hydrogen embrittlement in steel interconnect plates in the electrochemical cells. Another topic of interest is if applying surface oxide scales on the metallic components in electrochemical cells can help protecting against corrosion due to ammonia. It is also assumed beneficial for handling and costs if more components in fuel cell stacks could be produced in polymers instead of steel.
Materials for end use applications in onshore and maritime transportation will be primarily the same as for production and hydrogen transport and storage. Hence challenges here may be related to the lifetime of fuel cells and piping.
– In pipeline transport of hydrogen, it is well established that mechanical properties of metallic materials and their weldments are impaired by hydrogen ingress. A central question is thus whether we can avoid or reduce the amount of hydrogen atoms entering the metal, says Vigdis.
– Will for instance the presence of impurities like O2 and CO in the H2-gas ensure a stable oxide layer on the steel surface and shield the steel from absorbing hydrogen? And what about the polymer (epoxy) flow coating on the inside of transport pipelines, will it withstand the influence of hydrogen or degrade and go into the gas stream? She asks.
There are many factors to consider when designing hydrogen infrastructure and selecting materials. HYDROGENi´s study maps out known challenges and knowledge gaps for various materials that come into contact with hydrogen and ammonia.
Those interested in learning more about the topic can contact HYDROGENi through Vigdis Olden.
