Embrittlement is a problem at high pressure because the stuff being embrittled has to be strong to contain pressure. Take away the pressure, and it only needs t

Embrittlement is a problem at high pressure because the stuff being embrittled has to be strong to contain pressure. Take away the pressure, and it only needs to not have holes in it. For decades, lamp gas -- carbon monoxide and hydrogen - was piped to homes, factories, offices, and ... street lamps, in cast -iron pipes. Then they switched to methane, same cast-iron pipes. They started out pretty brittle, really. Still in use, though.