Development of an experimental setup for testing X52 steel SENT specimens in electrolytic hydrogen to explore repurposing potential of pipelines

Hydrogen is considered a key alternative to fossil fuels in the broader context of ecological transition. Repurposing natural gas pipelines for hydrogen transport is one of the challenges of this approach. However, hydrogen can diffuse into metallic lattices, leading to hydrogen embrittlement (HE). For this reason, typically ductile materials can experience unexpected brittle fractures, and it is therefore necessary to assess the HE propensity of the current pipeline network to ensure its fitness for hydrogen transport. This study examines the relationship between the microstructure of the circumferential weld joint in X52 pipeline steel and hydrogen concentration, introduced electrolytically. Base material, heat affected zone and fused zone were subjected to 1800, 3600, 7200 and 14400 s of continuous charging with a current density J = −10 mA/cm 2 in an acid solution. Results showed that the fusion zone absorbed the most hydrogen across all charging times, while the base material absorbed more hydrogen than the heat-affected zone due to the presence of non-metallic inclusions. Fracture toughness was assessed using single edge notch tension specimens (SENT) in air and electrolytic hydrogen. Results indicate that the base material is particularly vulnerable to hydrogen environments, exhibiting the greatest reduction in toughness when exposed to hydrogen compared to air. • Develope an experimental setup for SENT fracture toughness tests in electrolytic hydrogen. • Identified optimal hydrogen charging conditions, introducing approximately 1 ppm H/h into base material. • Fused zone charge more hydrogen than base material and heat affected zone, showing a lower toughness drop in hydrogen environments. • Hydrogen embrittlement susceptibility was highest in base material, as evidenced by fracture mechanics tests. • Vintage X52 steel exhibit reasonable hydrogen compatibility under 60–80 bar, indicating potential for hydrogen transport repurposing.