3.2.4 Materials selection for installation

Materials used for the installation of hydrogen and fuel cell equipment must be suitable for such application during the scheduled lifetime unless replacement is foreseen.

Where necessary, adequate allowance or protection against corrosion or other chemical attack must be provided, taking due account of the intended and reasonably foreseeable use. Hydrogen gas dissolved in liquids will permeate into adjoining vessel materials. At elevated temperatures and pressures, hydrogen attacks mild steels severely, causing decarburisation and embrittlement.  It is, therefore, vital that if hydrogen is stored or handled under pressure compatible materials, e.g. special alloy steels, are used for pipe work, vessels, etc.