Noticing Rust on Elbow

Hi Guys, I am up and running for the first time for about a week. I have a stoker rear venting into a masonry, clay lined chimney. I installed black stove pipe and a black stove elbow where the straight pipe meets the stove exhaust. The elbow is a 3-4 piece type elbow with sections that rotate to get the angle that you need. I just started noticing tan discoloration appearing where the rotating seams of a couple of the elbow sections meet. Is this normal? Is it a problem? I don't see or smell any exhaust and the carbon monoxide monitor thankfully reads zero. Thanks!

probably just some fly ash, the pipe is normally under vacuum, so, No, it shouldn't be a problem. Maybe some moisture getting down the chimney and picking up of the ash and leaking out?

Can you post pics? I have the same kind of elbows. Maybe there is a lot of moisture in your exhaust stream or condensation is happening somehow. If the crimped end of your elbow is facing the stove, the male parts of the sections should be facing down, which might reduce the chance of moisture coming out of the sections or stack. I'm sure more expert advice than mine will follow.

Burning coal, I won't use anything other than 316 grade stainless steel. I currently have 304 SS pipe & even that has small perforations in it from corrosion after being on it's 3rd winter. Black stovepipe sucks. You can buy it cheap, then continuously replace it......or spend some $$$ & never do it again.

Here's what my black stovepipe looked like after one winter in a damp basement....

sorry for the poor quality pics and they would need to be rotated 90 degrees to the left but in the first pic it is at the bottom as the pipe starts to turn horizontal and the second pic is near the bottom also- both along the seams. It seems to be a very minor case of what Smity has although my elbow is inside and is not subject to dampness unless the damage was done before I began burning

I'm still running my SS pipe with all the little holes in it. If you have a decent draft, there is no way it will leak CO into the house......unless there's a downdraft. In my case, whenever the oil boiler kicks on it puffs back for a split second, at the instant the oil ignites. More of it comes out my glass vents than the holey pipe, though.

Forgot to add: I used to have downdrafting issues until I installed a chimney cap.

Wow Smitty that is nasty.

It is! Just 1 summer of being unused in the basement & that's what I found in the fall!

Here is a pic of my current pipe. You can see the darker circular patterns on the pipe -- those are open holes. Most of the damage was from that first season of use, because I did the same thing I did with the black pipe -- just left it hooked up & no cleaned for the summer ( I figured there was no way SS would corrode... ). Now, I clean the pipe, spray a baking soda / water mix on it & store it upstairs.