Rusting Black Stove Pipe

I noticed today that our black single wall stove pipe has rust spots and rusty pimples all over the pipe on the outside.
The single wall pipe is the only pipe that we can easily see as the rest goes through the ceiling into the triple wall ss pipe that is the chimney pipe.

the whole system is 4 or 5 yrs old. What is the life expectancy of this type of setup? Does the rust mean that it's going to be unsafe to use this up coming winter?
Does it need replaced?

If there are rusty pimples, there's a good chance there are pinholes underneath that rust, if so, the safest thing is to replace it.

Yes, replace it, don't try & analyze it!! Pipe is a lot smarter the us, it knows when it's time! I do my exposed black pipe every 3 yrs just because I can.

I was thinking that. It looks like the ceiling box where the single wall goes to triple wall is ok.
It's just a few feet of the single wall black pipe. How long should that last?

Also, my chimney cap is rusting, It appears that the install used a non stainless cap on top of the pipe. I was thinking of replacing the outside cap with a stainless cap to help with the rusting.

How long on the black pipe?? I got 2 1/2 lengths. Till it starts rusting. My double wall is goin on 11 yrs. When the cap is missing some day, I'd suggest replacing it. Until then---nah.

Pop the pimples and see if you can get an awl into it. If you can, it's junk.

Humrm, coal exhaust residue on iron plus h2o equals sulfuric acid...remove one or more of 3 things and the new pipe can last indefinitely.

1, remove iron containing pipe
2. remove moisture
3.remove residue

BTW: stainless will cost a lot more and last a tiny bit longer but, acid will win in the end.

I was thinking about the cap because it seems to be making a mess and helping to cause my shingles to brown around the stainless pipe.
I would love to find away to replace the pipe with a masonry chimney so I don't have to replace the black pipe every couple years -- even though it's not expensive.
its the cost of replacing the stainless pipe that really gets expensive .

Under normal operating conditions, I've heard the SS systems will outlast us. As for the staining from the cap, if you're not looking to replace due to the expense, maybe you could paint it with some Rustoleum to get you by. They might have some hot paint. Don't believe the cap gets that hot, in the winter.

Lifetime of your black stove pipe is contingent on how well you take care of it at the end of the burning season. What you don't want is to leave fly ash clinging to it thru the hot humid summer as McGiever pointed out.

At the end of each season I take all my black stove pipe down, haul it outside and scrub the inside with a mild soap solution and rinse it with the hose. Then I'll let it bake in the sunshine and dry completely. Then it gets stored in the attic till October. I use the heavier gauge stove pipe I ordered it online. It should last 8-10 years as long as I take good care of it every spring. Otherwise I've seen it disintegrate in one summer.

I should add that I have a very bad environment in my basement, if I were to leave it down there all summer.

Miles may vary.

well the last couple years I cleaned the pipe.
Thinking back this past year, I did not clean the pipe.
I guess that did not help the situation.

It is best to remove it, clean and store it. Reinstall it when your ready to heat. I don't bother with mine but have to change it every 4-5 years.

I follow what Lightning said. In addition, I coat the inside with fluid film for the summer rest. This year I stored it in my shed out in the woods, it has a timber floor and stays quite dry, Previously I used the attic, but now I have a good through the chimney pipe wall thermometer and did not want to stress it all summer with attic heat. I also use 22 gauge.

Ditto--3 or 4 yrs. I just dry brush mine w/ chimney brush & put it right back on the stove. I have excellent draft. Keep MPD closed off season. There is never excess/any rust, like stated, I just do it.

I don't think the brown stuff on your shingles is
from the steel cap.Some of us burning
coal get it even with Stainless caps.I have
a Stainless cap and have the rusty streak.