The exhaust-system on my diesel is all original and I live in the rust-belt
The car lived all its life here...
Also had a W124 230E back home (Indonesia - right along the equator). It was not too humid but the muffler kept rusting and created many holes that kept getting patched until one day it fell off when I started the engine...
I always wondered bout that too.
Whenever I see gas cars here they throw out a lot of water vapor and some just drip water from the exhaust pipes. The diesels don't do that
They have their own smoke hehehe..