The real problem here is wear. You're not going to run a machine for hundreds of years without spare parts. So either you need several dozen machines to cannibalize them to keep one running, or you need the technology to manufacture spares. But that shouldn't actually be too hard if you say it's mostly industrial era technology. I.e. no electronics, hardly any micromachinery. The biggest problem would be raw material, since turning iron ore into steel is a process that cannot be efficiently done on a small scale, but if you can just salvage steel from somehwere else (i.e. broken machine parts) just turning that into spare parts would be vastly easier. Heck, if you can melt down steel, you can even reuse the broken parts as raw material, the actual material loss is pretty insignificant.
Physical erosion in 600 years is pretty unlikely unless you get sahara-like sandstorms. Rain and damp however will turn unprotected metal into piles of rust. Or more like ruststains on the floor. I'd alos be curious how the environment is so dangerous it can kill a human in a few seconds. If its something physical it should affect the metal too maybe? If there's corrosive gases in the atmosphere for example.
Anyway, the important part for preserving metal is that it is kept reasonably dry. The thermal stresses would most likely damage any machinery to a point where it won't work, however that should be easily repairable, maybe all you need is to correct some dents with a hammer, if you're lucky. A bigger problem with temperature is, again, water. But a dry space underground should preserve metal well enough to make machines worth salvaging.