Comment by akiselev
7 years ago
Not just any opening: just about any microscopic crack would let it out and most non-metal materials are effectively porous when trying to contain helium under pressure. It's even used to detect leaks in high vacuum chambers.
You don’t even need cracks. Helium (and hydrogen) can diffuse through metal, especially at high temperatures. Hydrogen embrittlement is a problem for processes that use high temp hiydrogen like the Haber process.
how is it typically dealt with? regular annealing?
I’m not sure about in modern processes, but Bosch’s original solution for the Haber-Bosch industrial process was to just periodical replace an expendable steel liner in the reaction vessel.