i didnt find anything about this when i searched for it. the only thing that i found in the search that included rust was about wheels and brakes. but has this happened to anyone? i have an eisenmann on my car, and i just really noticed it today. on the bottom on the inside of the left tip, there's some rusting going on. what can cause this? anything i can do? any input is appreciated. thanks in advance.

 

overheating from the welding of the pipe to the exhaust. You're basically sc$#@ed unless it is still under warranty.

 

does it look like this?
http://www.m5board.com/vbulletin/showthread.php?t=91540

 

yeah it kind of looks like that, except more orange and white in color and is inside the exhaust tip.

 

It's experiencing decarburization. It happens with 304 as it cools after welding. Chromium carbides form (the carbon bonds with the chromium).

 

is it not the BMW muffler is made of grade A stainess steel

 

i swapped the bmw muffler for an axle back eisenmann. anyway.. thanks for the input guys. jet190rs and that link he provided and black525i were right. thanks again.