[aerojoe23]

I thought H2 under pressure still embrittled metal. But it isn't an area I study, I'd like to read more about it.

[samtho]

There will be the occasional free H+ ion but most of them will have paired off. Given a long enough time, there could be a small amount of damage done to the metal. There are ways to get around this by positively charging the vessel or using certain types of metals with a strong positive charge.