[MontrealFRS]

So I went outside this morning and took a picture of my car from far and noticed brown spots on the pipes after the muffler going to the midpipe.
As I came close I realised it was surface rust pretty much all over the piping...
I live in montreal quebec and I got destroyed by salt /snow... ext but ive only had this exhaust for like 6-7 months and have bought exhausts before and never had this problem.
So i did my research on the greddy thinking it was all 304ss.... but to my surprise...
only the mufflers come t304 and the rest of the piping is t409..
What can I do to prevent this from getting worse?? Is there a way to clean the surface or not do anything.?( The mufflers are intact and shiny btw ).