Armor exhausts: to rust or not to rust?

[Minsk94]

Armor scale modelers love to cover mufflers and exhaust pipes of their models in significant layers of rust. But the question is: would they really rust so badly? If in beginning they were painted just like the rest of a vehicle, we need to allow some time for the paint to pill of. Now, a deep rust will not set in in a matter of a day, that may take a while too. Not to mention that military vehicles were constantly cleaned and repainted. On top of that we can add a short life span of those vehicles as well (they may not even survive long enough for rust to appear).

So the question is: would those exhausts rust as bad as we try to present them? Maybe they were just dirtier, but not rustier?

[sdimmick]

Given the temperature (700 to 1200 degrees depending on Diesel vs Gas powered) that they are exposed and quality of materials used, rust would set in with in a couple days of of the vehicle being used. It wouldn't have the tonal values/brightness that modelers like to depict, it would be more along the lines of a dull brown color like tracks are. Look at an older car (IE one that is over 20 years old or so) that doesn't have a stainless steel exhaust to get a good idea.

[Minsk94]

That would also depend on the weather and local climate. But even on the cars exhaust pipe doesn't get rusted within couple of days. Otherwise it would rust through within several months. But obviously the material used to make a pipe will play a big role too, no questions there.
Little bit off the subject, but why would the tracks be brown?

[sdimmick]

[quote="Minsk94"
Little bit off the subject, but why would the tracks be brown?[/quote]

Its a catch-all color...I've seen tracks range to a polished steel to a very rusty color, depending on operating environment.
IMO its also a good color for scale modelling tracks