Up here in the rust belt, everything gets rusty, especially exhaust systems. And when we need to replace part of the exhaust, it often requires heating up the nuts and bolts that hold it together so they’ll come apart.
On this one I heated up the nuts and took the bolts out with my air wrench, and as you can see, where the nuts were is completely burned up and unusable. On another car, I could only get one of the bolts out and had to torch the other completely out. Yes, that means heating it until it melts out of where it was. Makes a nice shower of sparks, always fun.