Gary Wrote: "The only place we have any hope of finding alien hardware is in deep space where the only weathering was due to micrometeors."

I have to disagree with you. if it crashed in the polar regions it could get encased in ice, in a desert, covered by sand, in a tar pit preserved like a fossil. Even in an ancient pine forest preserved in amber.

Even at certain depths of the ocean the oxygen content is pretty low and it takes quite a while to rust away, that is if it was a rustable metal.
See info on the wreck of the aircraft carrier York Town.

Did you see that comercial about how long it takes for certain things to decompose?

I had this sci fi idea that pieces of rare metals like platinum and titanium could be pieces of an ancient spacecraft that got blown up in a war in outer space and rained down on Earth, melted into the tectonic plates regurgitated by volcanism, mined by humans, and made into parts of space craft. Now that's recycling!

Of course I don't believe this is the case in real life.