Stainless T discoloration

[Dune]

It seriously reduces the corrosion resistance of the metal If it is just the tee that is not a big deal really but if it is the liner to it can be a problem.

The corrosion resistance of stainless steel is based upon the impermeability of surface oxides.

http://scienceline.ucsb.edu/getkey.php?key=372

 

[transmogrifire]

pretend it has a liner and you can't see the dicolouration. I'm sure if i split my class A apart it would look similar or worse.

 

[bholler]

Ok guys you obviously know more about the properties of the metals used in the liner products than the engineers from olympia i just talked to last week I apologize for the misunderstanding

 

[begreen]

I can't understand why in that pic the tee and snout are discolored but the liner appears to not be discolored.

That is what led me to suspect the downward slope of the snout. Using an IR thermometer, I've found that heat pockets at the top of the pipe when this happens. My guess is that this is due to the slowing down of the hot flue gases.

 

[bholler]

That is what led me to suspect the downward slope of the snout. I have found that heat pockets at the top of the pipe when this happens.

I have never seen it but it does make sense i could see how it could happen for sure

 

[Oldman47]

I read through that reference Dune and do not see anything in it that claims that discolored stainless is somehow degraded. It does talk about chromium being the main player in making stainless be stainless. On the other hand have a look at any older motorcycle exhaust and you will see that it is a solid blue for several inches after the pipe leaves the exhaust port of the engine. I am talking about a mild steel pipe with a chrome corrosion resistant coating turning a deep blue in the first week of use. It never rusts out any faster than the rest of the pipe even though it is that deep blue for most of its life. My first bike ever I went crazy trying to clean off that blue color but it is the color of the oxidized chrome coating and I was wasting my time trying to remove it. The pipes will rust but it happens where the chrome coating gets scratched regardless of the color not due to heat damage of the chrome coating. Newer bikes use stainless pipes with heat shields so you can't see the blue color but it is still there under the cool running chromed covers.

 

[Dune]

I read through that reference Dune and do not see anything in it that claims that discolored stainless is somehow degraded. It does talk about chromium being the main player in making stainless be stainless. On the other hand have a look at any older motorcycle exhaust and you will see that it is a solid blue for several inches after the pipe leaves the exhaust port of the engine. I am talking about a mild steel pipe with a chrome corrosion resistant coating turning a deep blue in the first week of use. It never rusts out any faster than the rest of the pipe even though it is that deep blue for most of its life. My first bike ever I went crazy trying to clean off that blue color but it is the color of the oxidized chrome coating and I was wasting my time trying to remove it. The pipes will rust but it happens where the chrome coating gets scratched regardless of the color not due to heat damage of the chrome coating. Newer bikes use stainless pipes with heat shields so you can't see the blue color but it is still there under the cool running chromed covers.

I know.

 

[Dune]

Ok guys you obviously know more about the properties of the metals used in the liner products than the engineers from olympia i just talked to last week I apologize for the misunderstanding

I am a contentious person in general and I try very hard to be neutral or just stay out of things on this site out of respect for my friend Craig, who founded this site and the great crew of moderators he assembled here. You obviously know more than the average bear about wood stoves and your input is valued here but I assure you that the corrosion resistance of stainless steel is intact after discoloration as long as it isn't exposed to a corrosive environment. The notion that bluing of the pipe has somehow reduced it to a lesser state is utterly ridiculous and is clearly the sentiment of some know it all engineer. FYI there are a lot of engineers on this site.

If you like, I could write an entire paper on the oxidation properties of stainless steel since I have been a custom fabricator specializing in S.S. for over 30 years.

It is a great selling point though, I guess.

 

[fire_man]

the corrosion resistance of stainless steel is intact after discoloration as long as it isn't exposed to a corrosive environment.

Does this imply if one had a coal burning stove (ie a more corrosive fuel) that there would be more concern than for a wood burning stove?

 

[JayD]

My thoughts are off gassing of oils in the manufacturing or just handling or wiping down with a dirty rag before it was heated caused the discoloration

 

[bholler]

I assure you that the corrosion resistance of stainless steel is intact after discoloration as long as it isn't exposed to a corrosive environment

And what would you call an environment In which the stainless is constantly exposed to corrosive gasses? Wood some is corrosive that is why we use stainless in the first place.

Does this imply if one had a coal burning stove (ie a more corrosive fuel) that there would be more concern than for a wood burning stove?

Yes coal will eat up compromised or improper alloy stainless pretty quickly.

 

[surfing woodsman]

From my experience with stainless steel is that the pipe will be fine and this discoloration should not be an issue. My drag car has stainless headers and although the steel is thicker we have exhaust temperatures of 1300 degrees and have no failures in the material while burning alcohol and methanol. We have had these temperatures for several hundred passes so I would say that there is nothing to worry about. Just my opinion

 

[bholler]

The notion that bluing of the pipe has somehow reduced it to a lesser state is utterly ridiculous and is clearly the sentiment of some know it all engineer. FYI there are a lot of engineers on this site.

If it was one engineer i would agree with you but i know of at least 4 companies that recommend replacement of blued pipe. I will readily admit that i am sure you know more about the material than me but if the manufacturer tells me that if it is blued that the metal is compromised who am i to say they are wrong. And i also have said here that i think it will probably be ok but it needs fully inspected to make sure and the situation needs monitored. In this case it looks like it is only the tee any way which honestly could have been done out of black pipe so i dont see any problem with leaving it if that is the only issue.

 

[perfoliate]

Just to throw one more log on the fire. We manufacture equipment designed to be run in hazardous locations. Our temps run 300-600 degrees Celsius continuously 24/7 365 days a year for years and years. The stainless steel heat exchangers are in and past that discoloration range. They flow hazardous vapors into the catalyst in the range of 50 to 700 scfm and back out without issue or any real degradation of the stainless steel. If there was we would be out of business. Having said that if there is excessive moisture or truly corrosive solvents run through it, it can become compromised but I wouldn't expect anything like that coming out of a woodstove.

 

[Dune]

That is what led me to suspect the downward slope of the snout. Using an IR thermometer, I've found that heat pockets at the top of the pipe when this happens. My guess is that this is due to the slowing down of the hot flue gases.

Or to flame impingement.

And what would you call an environment In which the stainless is constantly exposed to corrosive gasses? Wood some is corrosive that is why we use stainless in the first place.



Yes coal will eat up compromised or improper alloy stainless pretty quickly.

Not corrosive enough to affect 26 gauge steel pipe for many, many years.
I call that a benign environment for 18-8 S.S. Coal on the other hand, could potentially produce sulphuric or carbonic acid which would indeed be a corrosive environment.

 

[perfoliate]

My guess is the replacement policy is all about liability. They have no way to know what your environment is like, how hot it got or the final condition of the product. Easier to just have a blanket policy to recommend replacement in all cases.

 

[Dune]

Does this imply if one had a coal burning stove (ie a more corrosive fuel) that there would be more concern than for a wood burning stove?

There is a coal burning stove in Brewster in the general store on Rt. 6A at the intersection of Rt. 124. If I remember correctly it is a Glenwood Baseheater, can't remember the model name, but it is big (as is the general store). The steel smoke pipe hasn't been replaced in 15 years that I know of.

On the other claw, I am installing a coal stove in my boat (also a Glenwood [yehaw]) and due to the input of bholler I am using stainless steel for the entire flue.
The boat is a corrosive environment nevermind what is going on inside the pipe.
Sorry to get all anecdotal but I love talking about all this stuff and who else would listen but you folks?

 

[perfoliate]

There is a coal burning stove in Brewster in the general store on Rt. 6A at the intersection of Rt. 124. If I remember correctly it is a Glenwood Baseheater, can't remember the model name, but it is big (as is the general store). The steel smoke pipe hasn't been replaced in 15 years that I know of.

On the other claw, I am installing a coal stove in my boat (also a Glenwood [yehaw]) and due to the input of bholler I am using stainless steel for the entire flue.
The boat is a corrosive environment nevermind what is going on inside the pipe.
Sorry to get all anecdotal but I love talking about all this stuff and who else would listen but you folks?

Gonna have to check that out next time I'm down cape. [emoji106]

 

[clark77]

Boy I really sparked a conversation here. I see and understand both views though. I do think that manufactures tend to side on the cautious side of things so for them to say replace if there's any discoloration, that's just the world we live in. Plus it puts more money in their pockets in sales.
With regards to the bluing, I've seen lots of headers with it on them for many many years. Yes that's not a flue pipe but it's similar.
I will probably end up getting a new tee at some point but not while I'm in the middle of the burning season. I have to trim the flex liner so I'll prob just do it when the weather gets warm.
I appreciate everyone's feedback on this and there's not a cut and dry answer on what to do.

 

[bholler]

Not corrosive enough to affect 26 gauge steel pipe for many, many years.

I agree with that for sure i am not really worried about the tee but i thing that a good inspection of the liner is in order because it is so much thinner it will certainly fail much sooner than the tee. and the tee is visible anyway so you can see if something is going wrong with it.

 

[clark77]

last week I contacted Olympia Chimney supply since they are the ones who manufacture the current tee I am using. I first sent their customer service am email, and after their first response, I sent them the pictures I posted in this thread. After speaking with the Operations Manager, she replied back today saying they are not concerned with the discoloration due to it being used for wood burning. See below emails.

Sent: Sunday, February 22, 2015 4:51 PM
To: Customer Service
Subject: Email Form Submitted
Name:kevin
Subject:Question
Message:

I have a question regarding a forever flex TLF6 6" tee connector. I have a 1 week old stove and tee connector and I am starting to get discoloration. it actually happened all in one day and I noticed that the horizontal section was no longer level or slightly uphill out of the back of the stove but it was canted slightly downhill out of the back of the stove. what is the extent of discoloration that is still good. What colors are bad to have on the stainless? Thanks again. kevin

From: Lisa Devaney

Date:02/23/2015 9:50 AM (GMT-05:00)

To: "'[email protected]'"

Subject: RE: Email Form Submitted

Dear Kevin,

I asked our operations manger your inquiry and he said: Please let him know that some discoloration is perfectly normal. Stainless steel will turn various different colors depending on the amount of heat that is absorbs. These colors may range from brown to blue. The only concern would be if there is a very dark blue area and this would tell us that the metal got very hot.

I hope this has helped.

Lisa Devaney
Customer Service
Direct: (570) 504-7177
Fax: (866) 237-0593
(broken link removed)



Sent: Monday, February 23, 2015 7:40 PM
To: Lisa Devaney
Subject: RE: Email Form Submitted

Lisa,

Thank you for the quick response. Attached are two photos from my tee connector. Seems that my wife had the air wide open while letting the stove get up to temp. The stove was in the middle of the burn range (500-600) degrees. I think the flames reached portions of the tee. Can you show the operations manager the pictures and let me know what he says? Thank you for your time.

Kevin

From: [email protected]
Date: Wed, 25 Feb 2015 14:43:58 -0500
Subject: FW: Email Form Submitted

Dear Kevin,

Our operations manager says: This discoloration is definitely abnormal. The steel got very hot very fast. The heat was stuck in one area of the tee for quite some time. There was either a draft problem on start-up or some type of fire catalyst was used to get the initial fire going.

This color shows a temperature range somewhere between 1,500 and 2,000 degrees F.

And wanted to know:
please ask him how he started the first burn.

Lisa Devaney

Sent: Wednesday, February 25, 2015 11:04 PM
To: Lisa Devaney
Subject: RE: Email Form Submitted

I noticed the discoloration at the same time as when I noticed that the horizontal section of the tee was slanted downhill and not level or slightly above level like it was when it was installed. I asked my wife about it because she was the one who was burning the stove that day and she said that she had the air wide open (reloading during the middle of the day) and the flames were wrapping up around the secondary baffle. she said the stove top did not exceed 625 degrees during that time. she turned the air down after the stove got to that temp. no fire catalyst was used to get a fire going. the fire was started and has not gone out in the two weeks we have had this new stove.
I started my first burn on 2/13/15 and this did not happen until 2/19/15. prior to that date, there was no discoloration on the tee and I had the stove top burning from 400 degrees all the way to 700 degrees (this is the optimum range for burning with my stove). I started my first burn with crumpled news papers with several pieces of kindling on top, then as that burned down, I added smaller splits until a nice coal bed was formed.
I've spoken to a few stove people and they suggest that since the tee was slanted downward slightly, it let the gasses linger inside the tee instead of letting them escape upward through the flue pipe. causing the tee to get hot and discolor.
I'm not sure how I could have a stove top temp of 625 but have temps in the tee at over 1500 to 2000 degrees though.
I have since fixed the tee to have a slightly upward slant out of the stove so that the smoke/gases will escape up and out of the stove and tee connector.
I've spoken to a few stove/flue installers and stove dealers and they said that I shouldn't worry about the discoloration and that it will not have any ill effects on the tee connector. I just want to make sure of that with you guys since its a piece that you manufacture. let me know if I should replace immediately or if I can keep it or if I should replace after the burning season is over. I've been burning with it since the 19th and there has been no change in its color. thank you again for your time.

kevin

Dear Kevin,

Our operations manager replies:


The stove top temperature and the flue gas temperature will be quite different. There was definitely very hot glue gas stuck in the tee for quite some time. Since you are only burning wood I am not too concerned with the discoloration. The tee is made from 316 stainless so it will hold up to wood fires very well. The reason I was initially concerned is because stainless steel looses some of its anti corrosion properties after it hits elevated temperatures on multiple occasions. It would be concerning if you were burning coal or oil. I do not think you will have any future problems.

Thanks,
Steve Penatzer
Operations Manager

Lisa Devaney

Customer Service

 

[bholler]

well that answers that

 

[fire_man]

This is my brand new T after two or three hot fire with the bypass open for about 15 minutes - stovetop never got over 250F.
The orange stuff at the joint is a failed attempt at using High Temp silicon.

 

[Dune]

This is my brand new T after two or three hot fire with the bypass open for about 15 minutes - stovetop never got over 250F.
The orange stuff at the joint is a failed attempt at using High Temp silicon.

View attachment 155119

Why did you think you needed RTV?

 

[Wisneaky]

I bet if you had a probe thermometer in that pipe it would be over 1500 degrees. I have had my wood furnace temp read only 250 degrees, but pipe temp was over 700 degrees.