While allows have different physical properties like hardness relative to pure metals, their reactive qualities don't change a great deal - steel rusts just like iron, for example. Now, if you're reacting the trit with something else to make a different chemical compound, then maybe it won't react with air. Remember, allow != compound. When dealing when metals, you're usually working with alloys.
Ah, valid; probably should have realised that myself, but long day at work was long. >> /feebleexcuse
It could be that the outer hull and innermost structure (i.e. the bit you see in space and the bits you walk around in) are something quite markedly not-tritanium, if we want to try and handwave the instability at 'atmospheric temperatures', whatever the hell they actually are. Assuming that it's just room temperature with a mild margin of error, I guess it sorta works, though conduction and so on could quickly become a problem.
That having been said, :science: and :EVE:. As much as I really want to try and apply my knowledge of physics to explain some of the less hideous mechanics when I'm not busy with work, I tend to just turn a blind eye to things like cloaking or warp drives. I'm unsure if there's another course of action in tritanium's case -- although could it be that it's not necessarily
used for the hulls of (at least sub-capital) ships? That'd neatly sidestep the issue, since whether or not ships are space 'structures' as such is debatable.
inb4 I've missed some piece of PF, since I've only really been going off the item description for tritanium