Wood, Coal or Pellet Stove Corrosion During the Off Season

[bdhsfz6]

During the warm months when the stove is not in use, dampness enters from the chimney and causes corrosion. I tried using Damp Rid and other moisture absorbing products, but there is just too much moisture for this to be effective. The flue has a damper but it doesn't seal completely and moisture gets past. For the last few years, I started taking out a section of flue pipe between the chimney and stove to keep moisture out. This works but as you can imagine, it's a messy job and leaves the stove unusable until the flue pipe is replaced. Not convenient if you want a quick fire on a chilly spring or fall day.

I'm not aware of any damper that seals the flue completely. What do others do to protect their stoves from internal corrosion when not in use?

 

[ponytug]

Flue stopper.

 

[MAX-24-Dean]

We used to plug the stove pipe with wool, but we had sheep to sheer so it was always available.

 

[ponytug]

We used to plug the stove pipe with wool, but we had sheep to sheer so it was always available.

The fluestopper is made from hardy Yorkshire herdwick wool felt.

Chimney Sheep® Draught Excluders: Wool, Warmth & Savings

Block 93% of heat loss with BBA-approved Herdwick wool excluders. Cut bills, reduce noise & fit any chimney. Breathable, moth-proof & UK-made.

chimneysheep.co.uk

All the best,

Peter

 

[bdhsfz6]

The fluestopper is made from hardy Yorkshire herdwick wool felt.

Chimney Sheep® Draught Excluders: Wool, Warmth & Savings

Block 93% of heat loss with BBA-approved Herdwick wool excluders. Cut bills, reduce noise & fit any chimney. Breathable, moth-proof & UK-made.

chimneysheep.co.uk

All the best,

Peter

Looks interesting but how do you get it in the flue without removing the pipe. Can't do it from inside due to the stove design.

 

[ponytug]

Looks interesting but how do you get it in the flue without removing the pipe. Can't do it from inside due to the stove design.

They make other sizes and shapes, but my guess is that your stove has secondary/tertiary combustion, so that's not going to solve it for you then.

The only other blocking solution that I know of is actually capping the flue every spring and uncapping it in the fall. It works ok if you have decent access to the cap (flat roof, fixed ladders), but I'm guessing that's not the case.

Is it feasible to clean out the ashes and soot in the spring and then leave the door off or fully open? If not, would you consider coating the inside every spring with a stove blacking compound?

We had our damper tested recently and it leaked several hundred cfm@50Pa (standard conditions). That's just crazy high in my opinion. It has no seal, and the tolerances are +/- 3/8" or so.

All the best,

Peter

 

[CalG]

I always pull the stove flue pipe from the down stairs stove during summer. The front room stove is soapstone. During pre season cleaning, I have not noted corrosion under the condensed combustion products.

The chimney thimble is stuffed with fiber glass batting, just because it's at hand. Aluminum foil works also.

 

[Cycledude]

During the warm months when the stove is not in use, dampness enters from the chimney and causes corrosion. I tried using Damp Rid and other moisture absorbing products, but there is just too much moisture for this to be effective. The flue has a damper but it doesn't seal completely and moisture gets past. For the last few years, I started taking out a section of flue pipe between the chimney and stove to keep moisture out. This works but as you can imagine, it's a messy job and leaves the stove unusable until the flue pipe is replaced. Not convenient if you want a quick fire on a chilly spring or fall day.

I'm not aware of any damper that seals the flue completely. What do others do to protect their stoves from internal corrosion when not in use?

I have wood furnace in basement, rust inside the furnace is something I have never worried about, my furnace is over 40 years old

 

[oosik]

We are just too dry here to get any type of corrosion. You might consider using stainless steel stove pipe. I used double wall stainless on my wood stove. Simply for safety reasons.

 

[bdhsfz6]

it's not the pipe that corrodes, it's the inside of the stove. It's a Harman Magnum Stoker and uses ordinary 1/4" sheet steel for the fire box. Moisture combines with the coating of fine coal ash and makes sulfuric acid. It's impossible to completely clean ash from all the recesses in the stove so the best approach is to keep it dry.

Removing the flue pipe between the stove and chimney does the job but it's messy and leaves the stove unusable for the occasional fire on a cool spring or fall day.

I was hoping to find a mechanical damper that would completely seal the flue but would open easily to light a fire.

 

[gstrom99]

I really don't worry about it. I have a good chimney cap and clean my stainless chimney once a year. The first burn some years has a musty odor to it, but nothing after that.

What kind of chimney do you have? Do you have a cap? Can you get to the top of the chimney, to put some sort of "bag" over it? Kind of a pain, and not easily removed, for your "chilly spring/fall" burns, though...

 

[bdhsfz6]

I really don't worry about it. I have a good chimney cap and clean my stainless chimney once a year. The first burn some years has a musty odor to it, but nothing after that.

What kind of chimney do you have? Do you have a cap? Can you get to the top of the chimney, to put some sort of "bag" over it? Kind of a pain, and not easily removed, for your "chilly spring/fall" burns, though...

It's a masonry chimney that I can access from the roof but as you say, it's a hassle to do for an occasional fire.

 

[ponytug]

it's not the pipe that corrodes, it's the inside of the stove. It's a Harman Magnum Stoker and uses ordinary 1/4" sheet steel for the fire box. Moisture combines with the coating of fine coal ash and makes sulfuric acid. It's impossible to completely clean ash from all the recesses in the stove so the best approach is to keep it dry.

Removing the flue pipe between the stove and chimney does the job but it's messy and leaves the stove unusable for the occasional fire on a cool spring or fall day.

I was hoping to find a mechanical damper that would completely seal the flue but would open easily to light a fire.

Actually, the moisture plus ash gets you something closer to lye, pH 12ish. That plus the other salts in the ash is quite corrosive, even if it isn't acidic.

Random trivia: Different trees concentrates different ratios of elements, leaving different chemical composition of the ash. At one time, not only were ashes used to make lye, or something close to it (KOH), but also specific types of wood ashes were used to make pottery glazes of different colors.

Something to think about as you all burn your Yule logs...

All the best,

Peter

 

[Mtsoxfan]

keep an old style light bulb lit in firebox. How much electricity can it really use?
I use to use a lightbulb in a box with beer I was fermenting to maintain temp in winter. Never cared or even thought about cost...

 

[bdhsfz6]

Actually, the moisture plus ash gets you something closer to lye, pH 12ish. That plus the other salts in the ash is quite corrosive, even if it isn't acidic.

Random trivia: Different trees concentrates different ratios of elements, leaving different chemical composition of the ash. At one time, not only were ashes used to make lye, or something close to it (KOH), but also specific types of wood ashes were used to make pottery glazes of different colors.

Something to think about as you all burn your Yule logs...

All the best,

Peter

This is true with wood ash. Coal ash + moisture = h2s04, sulfuric acid.

 

[jyoutz]

keep an old style light bulb lit in firebox. How much electricity can it really use?
I use to use a lightbulb in a box with beer I was fermenting to maintain temp in winter. Never cared or even thought about cost...

Can incandescent bulbs still be found?

 

[ponytug]

This is true with wood ash. Coal ash + moisture = h2s04, sulfuric acid.

Ooops! My bad. I missed that you were heating with coal. Yes, the deposits on the stove higher up are acidic, and definitely corrosive. There isn't much to be done about that, I am afraid. Weekly fires all summer?

Not so great for making pottery glazes from the clinkers, either.

All the best,

Peter

 

[Mtsoxfan]

Can incandescent bulbs still be found?

I think I remember many years ago they were phasing them out. The CFL's are junk, IMHO. And there are so many expensive, but cheaply made LED's. 50000 hours my ass...

 

[jyoutz]

I think I remember many years ago they were phasing them out. The CFL's are junk, IMHO. And there are so many expensive, but cheaply made LED's. 50000 hours my ass...

I don’t know how long LEDs last in actual use. I can just say that I’ve never had one burn out.

 

[bdhsfz6]

Ooops! My bad. I missed that you were heating with coal. Yes, the deposits on the stove higher up are acidic, and definitely corrosive. There isn't much to be done about that, I am afraid. Weekly fires all summer?

Not so great for making pottery glazes from the clinkers, either.

All the best,

Peter

I guess I should explain the reason I posted the thread in the first place.

I used to light the coal stove in Nov and run it thru Apr with the occasional fire in Oct & May. I would remove the flue pipe in May and replace it in Oct to keep moisture out of the stove. This worked well for almost 40 years.

This year, the coal vs oil price isn't that much different. At my age, it's no longer worth the effort required to burn coal. I do like to have a backup heat source other than oil though. Than means it's important to keep the coal stove ready to go on a moments notice. Putting the flue pipe back in place just adds time & effort, and I'd like to simplify the process.

What started me thinking about this is, it was -9F here last Monday morning and the oil burner decided to quit. It would have been nice to light a coal fire while I worked on the oil furnace just in case it needed parts. The house could get quite cold during the 2 hour drive to town and back at -9 and a wind chill of -22. Luckily, it was just a failed cad cell which I had on hand. I was able to fix it in about 15 minutes. Could have been much worse.

I was hoping that someone knew of a mechanical device, similar to a damper, that would open and close a flue completely with the turn of a handle. That way, I could keep the stove stoked and ready to go with a turn of a handle and a match without worrying about corrosion from moisture.

I guess the best thing to do is to redesign the stove - chimney connection with a section of flue pipe that is more easily removed & replaced, and just deal with the mess.

Thanks to all who responded with ideas.