Investigation of hydrogen embrittlement of an API 5 L X52 pipeline through potentiostatic charging

The evolving global energy landscape, shaped by climate change and geopolitical challenges, accelerates the shift to renewable sources. Hydrogen is a promising energy carrier for retrofitting Europe's gas pipeline infrastructure at low cost. However, the susceptibility of steel pipelines to hydrogen embrittlement (HE) poses significant safety risks. This study presents a novel in situ methodology combining potentiostatic electrochemical charging and mechanical testing to investigate HE in vintage API 5 L X52 pipeline steel. The effects of electrolyte acidity, applied potential, and hydrogen recombination suppression were systematically explored and related to the absorption of ∼1 ppm of hydrogen simulating the critical operating condition in pipelines. This led to a sharp drop in ductility and transition to mixed-mode fracture with a brittle fracture evolving radially in the outer layer and progressing to a ductile core. Additionally, the role of MnS inclusions was confirmed not only as crack initiators but also as crack propagators, even under moderate hydrogen levels. These findings provide new insight into the interplay between microstructure, electrochemical parameters, and embrittlement behavior, with implications for the safe integration of hydrogen into legacy steel networks.