any word on DEF causing more rust out in exhausts?

[Dmace]

The urea goes in before the Catalytic converter, and it comes out as water vapor and nitrogen. There is no corrosion, burning fuel makes water. Let us try and stick to actual problems not making up things

Water + Metal = Rust
How can you say water in an exhaust system won't cause rust? Especially in the coldest part of the exhaust system...