Selection of Materials
Materials of construction, including materials used in valves and seals, must be carefully selected to account for their deterioration when exposed to hydrogen at the intended operating conditions.
The mechanical properties of metals, including steels, aluminum and aluminum alloys, titanium and titanium alloys, and nickel and nickel alloys are detrimentally affected by hydrogen.
Exposure of metals to hydrogen can lead to embrittlement, cracking and/or significant losses in tensile strength, ductility, and fracture toughness. This can result in premature failure in load-carrying components. See discussions of hydrogen embrittlement for compressed gas systems and cryogenic liquid systems in the Hydrogen Storage and Piping Systems section.
Additionally, hydrogen diffuses through many materials, particularly nonmetals, due to its small molecular size.