The little bit of corrosion is normal wear and tear. The exhaust system is made of aluminized steel so it will rust. But don't worry, the metal is very thick and the rust on the outside will not affect the performance or life of the muffler. Whenever exhaust systems get holes, it's from rotting from the INSIDE-OUT. Water condensation builds up inside the exhaust pipes whenever you start your car or let it sit for a while. If your exhaust doesn't get up to proper operating temperature for the proper amount of time, the water condensation just stays in your exhaust pipe. Then when you park it again, there is just a pool of water sitting in your pipes and causes it to rust from the inside out.
The rust on the outside is ugly but it won't affect the longevity of the muffler. It can probably be removed with some rust remover. You can maybe try spray painting it with some high temperature rust inhibitor.
The rust on the outside is ugly but it won't affect the longevity of the muffler. It can probably be removed with some rust remover. You can maybe try spray painting it with some high temperature rust inhibitor.