This Deliverable provides a comprehensive analysis of how hydrogen affects the performance and reliability of materials and components used in natural gas transmission and distribution networks. It examines hydrogen-induced failure modes and degradation mechanisms in both metallic and non-metallic materials under hydrogen exposure. The report consolidates experimental data from research studies, project results, and relevant standards to evaluate material behaviour in hydrogen-containing environments especially in the context of hydrogen blending in the gas grid. It also discusses the compatibility of various materials and components with hydrogen service, providing insights to support decision-making for the safe integration of hydrogen into existing gas infrastructure. The findings serve as a foundation for guiding future research, testing, and operational practices, aiding the transition toward hydrogen-enriched energy systems.
