Hydrogen barrier coatings for pure hydrogen/hydrogen-blended natural gas pipelines: a focused review

Constructing new hydrogen pipelines or utilizing existing natural gas networks represents an effective pathway for large-scale hydrogen energy transport. However, the permeation of hydrogen atoms into metallic materials during transport can induce hydrogen embrittlement (HE), posing a severe threat to pipeline safety. Developing hydrogen barrier coatings (HBCs) with superior pipeline adaptability is a critical strategy to mitigate this issue. This paper systematically reviews four HBC material systems: metal-based, ceramic-based, 2D materials, and polymer-based composites. Beyond a comparative analysis of their barrier performance, we deeply elucidate the hydrogen barrier mechanisms, including the physical/chemical barriers and hydrogen trapping effects in inorganic materials, as well as the synergistic mechanisms between organic polymer matrices and functional fillers. A key contribution of this review, which distinguishes it from existing literature, is the construction of a comprehensive full-chain evaluation framework. This framework integrates “Preparation Quality (density, adhesion, thickness) – Hydrogen Barrier Efficiency (permeation rate, permeation reduction factor) – Protection Performance (HE resistance, fatigue resistance) – Pipeline Applicability (environmental coupling, coating–substrate interactions)”, thereby providing a standardized basis for assessment. Finally, considering the specific requirements of hydrogen transport scenarios, the paper outlines current pipeline coating application requirements and proposes future research directions to support the development of safe and efficient hydrogen transport infrastructure.