This is nothing terribly important but I am just curious: is it possible to turn rusty weapons into normal ones? To remove the rust somehow?

Unfortunately, no. Rustiness is a characteristic of those weapons, not a sign of wear; they have a fixed number of HPs, and repairing any further damage simply returns them to their as-found condition.

It's exactly as strange as being able to charm ailing wolves into becoming your familiars, and (instead of winding up with healthy wolves at some point) watching them grow into Level 50 ailing wolf powerhouses.

Hmm, that's a pity. I always thought there was something you can do with these kinds of weapons, just didn't know what. It would be cool to find a super rare tech weapon hidden under the rust for example. There is even one junk dealer (in The Boil) who tells you something like "...a little spit and polish will clean them up just like new...". Anyways, thanks for your response!

No problem. I think they were added to the game to supply flavor, as in the idea that one of the downsides of technology is that mechanical things eventually wear out. Their stats (speed, damage, HPs, etc.) are always lower than even the most basic non-rusted version.

And one example of putting them to use would be leaving them lying around for your humanoid opponents to pick up right before you engage them. There are few things more amusing than watching the Shrouded Hills bridge thieves try to attack your party while hampered by rusty spikes, for example.