Material Selection

Designers of high-pressure hydrogen storage vessels and piping systems should understand the effect of hydrogen exposure to materials (e.g., hydrogen embrittlement) in order to make appropriate material selections. Note that certain surface finishing techniques (e.g., electro-polishing) and welding may introduce hydrogen into a metal, resulting in accelerated embrittlement.

Generally acceptable materials include austenitic stainless steels, aluminum alloys, copper, and copper alloys.

Nickel and most nickel alloys should not be used since they are subject to severe hydrogen embrittlement.

Gray, ductile, and malleable cast irons should not be used for hydrogen service.

Materials should be carefully selected using good quality control procedures and with a clear understanding of the specific storage system or piping system operating conditions.

Ideally, testing (i.e., direct exposure of the material to hydrogen) and analysis should be done to assure that the material will perform as expected at planned operating conditions as well as worst-case conditions. If testing isn't practical, referring to existing material selection guidance found in the literature may provide the needed assurance.