A critical review of hydrogen-induced cracking (HIC) of API 5L pipeline steel grades in the oil and gas industry

Hydrogen-induced cracking (HIC) poses a significant threat to the integrity of carbon steel components, such as pipelines and pressure vessels, particularly in hydrogen-rich and sour service environments containing hydrogen sulfide (H₂S) in the oil and gas industry. Although HIC damage is a serious threat to the integrity and reliability of oil and gas pipelines and other steel components, most research focuses on another hydrogen damage mechanism, i.e., hydrogen embrittlement (HE). This comprehensive critical review paper brings this research gap and explores all of the critical aspects of multifaceted HIC phenomena in API 5L pipeline steels, including update on (1) mechanisms of HIC; (2) critical factors affecting HIC susceptibility; (3) standardized testing methods (NACE TM0284 and slow strain rate testing (SSRT)) and advanced testing methods; (4) techniques for inspection of HIC; and (5) various HIC mitigation strategies. Particular attention is given to the hydrogen-related pipeline failure and hydrogen environmentally assisted cracking (HEAC) modes in the presence or absence of external stresses due to various forms of HIC, with detailed analyses of (1) hydrogen blistering (HB) and delamination (HD); (2) hydrogen stress cracking (HSC), often referred as types 1 and 2 sulfide stress cracking (SSC) in presence of H₂S; (3) stress-oriented hydrogen-induced cracking (SOHIC); and (4) synergy of hydrogen damage mechanisms (HIC + HE). A detailed analysis of the influence of microstructure, alloying elements, inclusions, precipitates, and environmental factors (pH, temperature, and H₂S) on hydrogen diffusion and trapping processes, critical hydrogen concentration and distribution, as well as HIC initiation and propagation, is also provided. The review critically discusses the challenges in mitigating HIC and the efficacy of existing prediction models and inspection tools for assessing HIC damages, providing a guideline for steel selection in critical hydrogen transportation and storage applications. We proposed a novel and integrated HIC mitigation strategy for pipeline steels, based on both contemporary theoretical (experimental and modeling) and practical in situ approaches. This seminal review paper advocates collaboration, standardization, and the development of innovative predictive HIC mitigation management. It provides comprehensive guidelines for both scientists and industrial partners to enhance the maintenance strategies and safety of carbon steels exposed to hydrogen-rich environments during exploitation.