And yet another problem with hydrogen is that unlike helium it is reactive, including with some metals. And those metals tend to become brittle fall apart after

And yet another problem with hydrogen is that unlike helium it is reactive, including with some metals. And those metals tend to become brittle fall apart after a while: https://en.wikipedia.org/wiki/Hydrogen_embrittlement https://en.wikipedia.org/wiki/Hydrogen_embrittlement