Painting a NOS muffler

[K8096]

I have new a stainless steel exhaust system I'm putting on a '41 Cadillac, but I want to use a NOS muffler with it.  I bought 2 of them at Hershey a few years back, in the original boxes.  If I wanted to put a coat of high temp paint on the muffler, what works best?  The car it's going on is a driver, not a show car.   

 

   

[Spinneyhill]

If you put stainless pipes onto those mufflers you will promote galvanic corrosion in the mufflers.  You will have to paint or zinc-alum plate them inside and out near the SS to prevent this, esp. inside - remember the amount if water vapour (and water!) in the exhaust of IC engines.

[Rusty_OToole]

Years ago I put a new Walker exhaust system on my daily driver pickup truck. Before I put it on I brushed on 2 coats of aluminum stove pipe paint I happened to have lying around. 10 years later there was NO rust on it anywhere. The first 2 or 3 feet was darker, discolored by heat but the paint was still on and still keeping off rust.

I would say, use any high temp paint you like. I'm sure there are lots better paints today than 30 year old stove pipe paint, and that was plenty good enough.

Plain steel pipes and mufflers with a couple of coats of paint will last practically as long as stainless, I believe. Maybe not literally but it should make them last 20 or 30 years.

Edited April 10, 2019 by Rusty_OToole (see edit history)

[wldavis]

I am definitely no paint expert, but the metal on your mufflers looks like it has been galvanized.  

The process (galvanization) is intended to stop rust.  I do not know if you can successfully paint

over galvanized metal.  Back when i was a kid, my dad got me to paint over the galvanized gutter

system on our house most every year, but house paint back in the '50s & '60s (enamel) would not

stay on it very long.

[Spinneyhill]

Yes, those mufflers are galvanised, which is why I was talking about galvanic corrosion. You can paint galvanised steel with the right paint. For galvanised steel roofs, etch primers are used. I used the same stuff to prime PVC downpipes on the water tanks. I am talking of house paint, but no doubt there are similar paints for automotive applications.

[Bloo]

I guess painting on the outside probably helps those of you who have salted roads. Out here in Washington State, sheetmetal mufflers rust out from the inside. They fill up with water from the combustion process, and if the owner only goes on short trips, or just uses the car occasionally, the water doesn't go away. It just stays there until the muffler rusts through. One trick is to drill a tiny hole at the lowest point. It must be tiny, too big and you will hear it.

 

This effect is worst on V engines with dual exhaust. You can expect the bottom to drop out of a sheetmetal muffler in 6 months on the heat riser side. It also happens quickly on cars that have the muffler all the way in the back.

[lump]

Most exhaust systems definitely rust from the inside out, as Bloo said. Just because a muffler doesn't show much rust on the outside, doesn't mean it isn't badly rusted inside. One day they may just fall off due to corrosion...yet even in that state they often look really nice on the outside...except a few small places where it rusted right through. 

 

By the way, you can paint over galvanize with zinc chromate primer, then your favorite top coat. But it will stink to high heaven until all such paint is fully baked on. 

[Rusty_OToole]

Old galvanized that is dull can be painted and the paint will stay on. Brand new shiny galvanized is different. New shiny stuff has a slick, greasy feel to it. Once it is dull and rough to the touch it is fine. On a galvanized roof that is out in the weather this takes about 6 months.

Edited April 13, 2019 by Rusty_OToole (see edit history)

[jpage]

I used Krylon high heat silver on my Model A system and it lasted fairly well, although I would touch it up every year. It was just plain unfinished steel and the Krylon did not burn off, even on the manifold.Try to get it at an industrial store. There seems to be a difference in the paint from the big box stores.

[FLYER15015]

Use POR-15 silver.

I painted my exhaust manifold on the '40 Buick about 5 years ago and it still looks new.

Mike in Colorado

[Kestrel]

Try this. I used this on old ugly galvanized  steel barn door tracks 15 years ago. They still look like new.

 

"16 oz spray, zinc-sele flat cold galvanizing compound, rust preventive zinc rich primer provides ultimate rust prevention on clean, lightly rusted or galvanized metal, protects like hot dip galvanizing, compatible with rust-oleum top coats."

[plymouthcranbrook]

I used High temp enamel on the exhaust of a 1992 Chevy after it was replaced and it lasted for 9 years and was still on the car when I sold it. Really just need to find out what the exhaust on a 2001 Chevy Astro was made of as mine with `192.000 miles on it is still all original. And in NE IL the salt is so thick in winter the roads are white.    

[Vila]

I use Bill Hirsch Exhaust and Manifold paint on all of my antique cars exhaust systems and it works great.  Some cars have the bright aluminum color and other the cast iron gray color.

 

I have always used it on Non-galvanized mild steel exhaust systems and am not sure about how it would hold up on a Galvanized system, but I would thing a quick call to them will answer that question. 

 

You can find their phone number at:   https://www.hirschauto.com/Exhaust-And-Manifold-Coatings/departments/13/