Penspen and National Gas Transmission Launch Study to Protect Hydrogen Infrastructure from Embrittlement

Penspen—that UK engineering consultancy everyone in pipeline integrity and energy transition circles knows—and National Gas Transmission—the folks who run Britain’s high-pressure gas network—teamed up on a gas inhibition study. Their mission? To tackle hydrogen embrittlement in existing steel pipes. With the UK sprinting towards zero-emission technology, repurposing over 6,000 km of natural gas corridors for hydrogen could be a real game-changer. But here’s the catch: high-pressure hydrogen can weaken steel, messing with its strength and safety. This partnership is zeroing in on impurity gases—think trace oxygen—to block atomic hydrogen and keep our pipelines in top shape as we shift to a low-carbon future.

Why Hydrogen Embrittlement Matters

Hydrogen embrittlement isn’t just a buzzword—it has real consequences. When atomic hydrogen sneaks into steel under pressure, it chips away at tensile strength, ductility and fracture toughness. Peer-reviewed studies show pipeline steels like X80 and L360 take a serious hit: elongation ratios drop to 0.50–0.78 in hydrogen versus air, and fatigue crack growth can more than double above 13 MPa. Left unchecked, embrittlement leads to brittle fractures and shortened pipeline lifespans—jeopardizing safety and putting big investments on the line.

Gas Inhibition: How It Works

The key idea behind this study is inhibitor gases. By adding tiny amounts of oxygen (O₂) into the hydrogen stream, you form a protective molecular layer on the steel. Oxygen molecules adsorb first, blocking hydrogen from dissociating and slipping into the microstructure. Lab tests have shown that the right O₂ partial pressure can slash hydrogen uptake—even in blends with CO₂, which otherwise accelerates embrittlement by forming corrosive carbonic acid. Penspen will use inline inspection tools and detailed materials analysis to map how gas mixtures, steel grades and weld microstructures affect inhibitor performance.

Strategic Implications for the UK’s Energy Transition

This isn’t just an academic exercise; it’s a practical lever for industrial decarbonization. Building entirely new hydrogen pipelines would cost tens of billions and take ages to permit and construct. Conversely, retrofitting 6,000+ km of existing network with gas inhibitors could unlock up to 20% hydrogen blends right away—delivering significant CO₂ savings and fast-tracking green hydrogen into power generation, heavy industry and transport. All of this uses our existing hydrogen infrastructure while paving the way for full conversion down the line.

Lessons from Decades of Research

Research into hydrogen embrittlement goes back over a century, then spiked in the 1970s with early hydrogen storage projects. Throughout, low-alloy steels like X52, X65 and X80—mainstays of transmission pipelines—have shown consistent vulnerability: elongation ratios drop to as low as 0.50–0.78 in hydrogen, and fatigue crack growth rates can double above 13 MPa. Weld heat-affected zones (HAZ) are particularly susceptible, with cracks propagating up to 30% faster than in base metal. These historic insights are now guiding the new gas inhibition trials, turning long-standing theory into real-world solutions.

Challenges and the Road Ahead

Rolling out gas inhibition across a vast network isn’t without its hurdles. Current gas quality specs limit oxygen to parts-per-million, so moving to percentage-level O₂ will need fresh guidelines from regulators and trade bodies. Plus, keeping an eye on inhibitor levels means ramping up sensor arrays and inline inspection tools—adding complexity, although still more cost-effective than building brand-new pipelines.

On the bright side, we’ve already got a skilled workforce in place. Asset managers, weld inspectors and integrity engineers who know natural gas inside out can pivot to hydrogen with minimal retraining—once they master the nuances of inhibitor management. In effect, this approach bridges today’s pipeline expertise with tomorrow’s vision for sustainable energy and large-scale hydrogen production.

By the time the study wraps up, Penspen and National Gas Transmission plan to release a best-practice guide detailing ideal inhibitor mixes, monitoring strategies and steel grade recommendations—a blueprint operators can use as they roll out zero-emission technology across their networks.

Ultimately, if this study hits its marks, it could be a real turning point. Instead of starting from scratch, operators could repurpose most of what’s already buried underground—cutting capex, slashing greenhouse gas emissions and helping the UK meet its ambitious net-zero targets. That’s the kind of practical innovation we need right now in the race to a sustainable energy future.

About

Penspen is a UK-based engineering consultancy founded in 1982. Known for its expertise in pipeline design, integrity management and energy transition projects, Penspen supports clients across oil, gas and emerging hydrogen sectors worldwide.

National Gas Transmission became its own entity in 2021 after taking on high-pressure gas transmission assets from National Grid. It’s now at the forefront of hydrogen blending, pipeline repurposing and gas compatibility research in the UK.