Effect of High-Pressure Hydrogen and Water Impurity on Aluminum Alloys

Abstract

Abstract Aluminum alloys are desirable in mobile fuel cell applications due to the combination of strength, hydrogen resistance, and low density. In dry hydrogen environments, the fatigue and fracture resistance of common structural aluminum alloys are not degraded compared to air environments. However, aluminum alloys can be susceptible to stress corrosion cracking in humid air, which raises questions about the potential deleterious effects of moisture impurities in high-pressure hydrogen environments. While this study does not address the effects of the air environment on aluminum hydrogen pressure components, we assess the fracture resistance of aluminum alloys in high-pressure hydrogen containing known amount of water. High-pressure gaseous hydrogen at pressure up to 100 MPa is shown to have no effect on elastic-plastic fracture measurements of common high-strength aluminum alloys in tempers designed for resistance to stress corrosion cracking. Complementary sustained load cracking tests in high-pressure hydrogen were also performed in gaseous hydrogen at pressure of approximately 100 MPa with water content near the maximum allowed in hydrogen standards for fuel cell vehicles. These tests show no evidence of environmental-assisted cracking at loading conditions approaching the onset of unstable fracture in this configuration. In summary, typical moisture content in fuel cell grade hydrogen (< 5 ppm) do not promote hydrogen-assisted fracture or stress corrosion cracking in the tested aluminum alloys.