True enough. But if the tracks were made of a ferrous metal that could rust/tarnish/oxidize, then, on the parts of the track that didn't come into contact with the ground, you could have some rather realistic weathering. As for spare track sections that are often mounted on the hull, some real rust would be nice.
But in general, I'm not talking about heavy rust that is a sign of neglect but just a light "dusting" so to speak.
ORIGINAL: brel
Never seen pictures of a tank with rust on it in service, all the rusty tank had been shot up during combat or target practice or were in the process of being cut up of at a metal breakers (scrap yard)
the only rusty bit on a tank would be the exhaust system(muffler)