As the world moves toward a hydrogen-based energy future, reusing existing pipeline infrastructure offers a cost-effective and sustainable solution for hydrogen transport. However, a major challenge lies in preventing hydrogen-induced cracking, which can compromise pipeline integrity.
The NoHENTRY project addresses this issue by developing advanced surface conditioning techniques to protect pipeline and compressor components from hydrogen damage, enabling safe and efficient reuse of current systems.
As the world transitions towards a hydrogen-based energy future, the need for effective and sustainable hydrogen transport solutions becomes increasingly important. One of the most promising ways to achieve this is through the reuse of existing pipeline infrastructure for hydrogen (H₂) transport. However, a critical challenge remains: the structural integrity of these pipelines may be compromised by hydrogen-induced cracks. These cracks are caused when hydrogen atoms are absorbed by the pipeline’s surface layer, potentially leading to material failure over time.
The NoHENTRY (No Hydrogen Entry) project aims to overcome this challenge by providing strategies for surface conditioning of the inner surfaces of existing pipelines and compressor components, making them resistant to hydrogen gas. This will allow the reuse of current pipeline systems for hydrogen transport in a cost-effective and climate-friendly manner.
Investigating hydrogen penetration: A multi-dimensional approach
At the core of the NoHENTRY project is a comprehensive understanding of the key parameters that influence hydrogen penetration through metallic and non-metallic surfaces. These include:
- Atomic-scale surface properties: Understanding how hydrogen atoms interact with the metal surface, particularly in the context of Fe-based alloys.
- Hydrogen dissociation, adsorption, and diffusion: The fundamental processes that control the material properties and determine hydrogen’s ability to infiltrate the pipeline.
The project combines advanced atomistic simulations with experimental evaluation, using real-world samples from serviced parts of the gas grid. This dual approach allows for a thorough analysis of how hydrogen behaves when in contact with different materials and surface conditions.
Early successes and promising results
In its first year, the NOHENTRY project has achieved several exciting milestones:
- Synthesis of unique alloys: The team successfully synthesized a series of binary and ternary alloys with a fully ferritic microstructure – without any second phases. This is a significant achievement, as the ferrite phase has a different stability region depending on the alloy’s composition. A carefully selected chemical composition and annealing treatment were used to isolate the effect of added elements on hydrogen interactions in the ferrite matrix. This approach is novel and has not been explored in hydrogen-related research before.
- First Results from Hydrogen Pick-Up Tests: Preliminary pick-up tests, conducted using high-pressure hydrogen charging in an autoclave, revealed key differences in alloy behaviour. These tests atmospherically reduce the thin oxide layer (present from atmospheric oxidation), producing a more metallic surface. X-ray Photoelectron Spectroscopy (XPS) measurements confirmed iron reduction reactions, allowing comparison of hydrogen uptake between oxidized and reduced surfaces for each binary alloy.
- Thermal desorption spectroscopy (TDS) quantification showed that hydrogen was primarily trapped in high-temperature traps in samples with a natural oxide layer. In contrast, samples with metallic (reduced) surfaces exhibited significantly lower hydrogen content, suggesting that surface oxides act as hydrogen storage layers. Clear differences between alloying elements were observed. This hypothesis of surface oxide stability was supported by XPS measurements, which confirmed the persistence of surface oxides in the more reactive alloys. As a result, hydrogen remains trapped within these surface oxide layers in the binary alloys containing more reactive metals.
- Next steps on hydrogen pick-up testing: Given the clear role of the oxide layer in hydrogen absorption, upcoming research will examine:
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- The impact of specific iron oxide phases and their trap energies through controlled oxide layer growth via annealing.
- The dynamics of reduction reactions and their influence on hydrogen trapping capacity.
- Development of a new permeation testing setup: To further investigate hydrogen-material interactions, a gaseous permeation cell was designed and constructed. The cell allows to extract fundamental hydrogen diffusion properties of a material by registering the amount of hydrogen that permeates through disks at different temperatures. Methodology is still under development, and testing protocols are being defined.
- Next steps on permeation testing: Upcoming experiments aim to identify and quantify hydrogen traps to understand how a material reacts to hydrogen exposure. Hydrogen traps and their associated trap energies are linked to specific defects (such as inclusions, second phases or grain boundaries) that are present in the microstructure of the material linked to specific microstructural features such as inclusions, grain boundaries, and second phases. Preliminary tests have demonstrated that trap energies can be reliably determined through temperature-dependent experiments, aligning well with literature values. The next objective is to examine how the chemical composition of the binary alloys influences the surface oxidation associated trap energies and, in turn, affects hydrogen interaction.
The path forward: A collaborative effort
In the final year of the project the aim is to integrate findings from both experimental techniques (pick-up and permeation testing) and computational modelling (DFT calculations performed by project partner University of Ghent).
Central to this effort are hydrogen trap defects at the surface & subsurface – which are key microstructural features that can be characterized through both methodologies. By combining these complementary perspectives, the project aims to build a comprehensive understanding of hydrogen behaviour in pipeline steels. These integrated insights will be consolidated and presented at the SteelyHydrogen 2025 conference.
This work has been performed as part of the NoHENTRY project, funded by the Energy Transition Fund (Energietransitiefonds) of the Directorate-General Energy (Algemene Directie Energie) of the Federal Public Service for the Economy (FOD Economie) of Belgium.
