alluminum paint on exhaust question

Mufflers (silencers in the UK) generally rust from the inside out, especially if the car is used for many short journeys. Water vapour in the exhaust condenses on cool surfaces (like the inside of the silencer) and if that surface does not get hot enough to burn off the water, the rusting process begins. Painting the outside will not prevent this.

Having said that, I believe that 'custom car' type shops sell exhaust manifold (headers for our friends across the pond) paint. If it will cope with the temperatures there, the silencer should not present a problem.

The middle muffler is double walled so the outer wall rust is not important.

The rear muffler is common to rust by the tailpipe... you can try the rust converter to neutralize that rust... but you probably can't extend the muffler's life by that much...

I typically get 7+ year on rear muffler... and more on center muffler... so with that much life, it is not worth the effort to try to save it.

thanks a lot for the tips. I mainly drive HWY 70miles a day. Given that, according to your reasoning, it will unlikely to rust from inside. The system is still solid, but the welding circumference is getting bad, esp. because I forgot the wash the underbody after last snow season.

Rust converter has been pretty effective in my other body project, but not sure it will work on the high-temp exhaust system. Will try.

I bought high-temp paint, but it all requires a baking at 500F for 2 hours, which is impossible for me. normal driving even hour-long idling wont deliver such high temp for needed cure.

again, many thanks for sharing your knowledge.