Painting Exhaust Components

[ARCHINSTL]

I will be getting a new Bosal catback (including muffler) and front pipe shortly.
While the existing system is quite rusty, it is intact and apparently not yet leaking, and should pass the safety inspection. Presuming it does, and does not fall off during the Winter, I should have some time to paint this.

Has anyone used OTC paint for exhaust pipes and the muffler? I'm talking something like Rust-Oleum's rattlecan Barbeque Grill Paint, which is supposed to be good for 1200 degrees. It is even available in five colors!
The instructions say nothing about a primer - just clean and scuff the surface. Since these parts will presumably be rustfree, it would seem to be the right time.

My AZ/ADV muffler is only 3 years old and already quite close to having perforations, despite (relatively) limited exposure to salt. I think the front pipe is OE, and presume the catback was replaced at some time. I replaced the cat in 2005 to pass the test - but it is really rusty - dunno if I will leave it in or replace it with a pipe. Emissions testing on mature cars is no longer required in MO - just safety.
I'd just like to get more life out of the system, as well as avoid getting a facefull of rust every time I'm under the system (and YES, I do wear safety glasses - ever since getting something in an eye in '07 while doing the muffler).
Tom M.

[4wdchico]

You might get some benefit if you paint the muffler and a little bit of the upstream pipe. The major front section of the system will get too hot for the paint to last very long.

OTOH, if you paint it now and let it sit all winter, the paint will be well cured when you do put the heat to it. It would be interesting to see how much paint was on the system after a good long high speed, or up hill, run.

[takza]

Most of the exhaust...as mentioned...gets real hot from the engine back to 6" or so after the cat...except for the doublewalled areas of the downpipe. Weak rust areas in the front part are where the downpipe clamps to the trans and maybe erosion of the pipes in and out of the cat...espec if it is aftermarket? Where it doesn't get hot...it is prone to rust....could be a good quality paint would help on this part. A welded muffler probably helps. My ss tubing is as good as new but discolored...except for where it was clamped some to hang it in the middle...but since it is oversized it makes little difference.

You'd need to clean the oil off the parts before painting them.

[ohcanada_00]

i recently painted an exhaust for a friend using stove paint. You can pick it up at any wood stove store and it comes in a pretty wide aray of colors. So far, its been really good. no flaking, no bubbles and looks killer. It scrubs well and looks nice even after a few months.

[keith]

If you want to prime it, use phosphoric acid. For mild steel, it will convert a few microns of the surface into iron phosphate which is a primary corrosion prevention and primer. Since iron phosphate is a metal, it won't burn off at exhaust temperature. The "conversion coating" as its known by, is not very pretty. It looks like corroded aluminum. Usually this conversion coating is sealed with a polymer sealant, but there are no sealers that I know of that will take over 450 F so the paint will have to be the sealer.

Some sources of phosphoric acid are "Navel Jelly", Allodine" and "Coca Cola". It works on SS but not quite as well. It depends on the grade of SS. It works better on the 4xx SS as they have more iron in them.

Wear rubber gloves, wipe the phosphoric into the metal with a soft nylon "scotchbrite" pad or use a good degreaser just before doing the conversion coating.