# Should I use Stainless or Galvanized chimney pipe?



## chris-mcpherson (Jun 21, 2010)

Some of it will be enclosed in a direct vent bump out and about 20' of it will be exposed. Doing the job in Stainless will cost me ~$400 more. Money is definitely an issue but I don't want it to cost me more in the long run.


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## madison (Jun 21, 2010)

I believe, stainless for the portions exposed to the elements and eye.  Otherwise, galvanized.  It was my understanding that the galvanized appearance will change with exposure to the rain/snow, but integrity is not affected.

I used galvanized inside, and painted it with high temp black.  Stainless outdoors.  Pics in sig. link.

Hope this helps.


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## chris-mcpherson (Jun 21, 2010)

That's what I thought about the integrity of the galvanized but, I have a supplier pushing the stainless with it's rust and corrosion resistance properties. I thought galvanized would hold up just as well. I figured it was an issue of aesthetics only.
Would it be advisable to paint galvanized pipe? If so, I could paint it the color of my house.


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## vvvv (Jun 21, 2010)

chris-mcpherson said:
			
		

> That's what I thought about the integrity of the galvanized but, I have a supplier pushing the stainless with it's rust and corrosion resistance properties. I thought galvanized would hold up just as well. I figured it was an issue of aesthetics only.
> Would it be advisable to paint galvanized pipe? If so, I could paint it the color of my house.


i would & keep extra paint on hand in case it peels


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## tiber (Jun 21, 2010)

You MUST paint galvanized. If you're looking for "hands free", you want stainless.

Myself, I want it to match the side of the house, and I don't want a blinding obilisk of light at dawn and dusk to piss off my neighbors, so I'm going to get galvanized.


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## chris-mcpherson (Jun 21, 2010)

tiber said:
			
		

> I don't want a blinding obilisk of light


Damn good point.
I was considering stainless so it would look shiny and new but it could end up being too much of a good thing. After consideration and the responses in this thread I'll use galvanized and paint it my house color.
Thanks guys.


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## madison (Jun 21, 2010)

I think high temp paint would be advised for fire resistance (? local codes ?) and longevity.  Which is going to add to the cost of the project.


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## chris-mcpherson (Jun 21, 2010)

Oh yeah...didn't think of that. Any idea what the approximate temp would be over half way up a 26' run would be?


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## DAKSY (Jun 22, 2010)

chris-mcpherson said:
			
		

> Oh yeah...didn't think of that. Any idea what the approximate temp would be over half way up a 26' run would be?



Hot enough that the Class A  will STILL require a 2" clearance to combustibles.


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## chris-mcpherson (Jun 22, 2010)

I was referring to the type of paint to use. Am I limited to hi-heat stove paint?
DAKSY...what part of NY are you at? I grew up in the Adirondacks.


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## tiber (Jun 22, 2010)

Well just high heat paint. Engine and brake paint comes in a variety of colors. Try Pep Boys, napa, etc.


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## madison (Jun 22, 2010)

Bar-bq paint as well is an option.

I personally would not want to try anything but high temp paint, during normal operation, the class a gets pretty warm, and i imagine if you screw up and get a chimney fire or stove overfire, you will blister the paint and possibly your home in the process.


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## DAKSY (Jun 22, 2010)

chris-mcpherson said:
			
		

> I was referring to the type of paint to use. Am I limited to hi-heat stove paint?
> DAKSY...what part of NY are you at? I grew up in the Adirondacks.



East of Albany in Rensselaer County...Averill Park...Actually live on Burden Lake. 
Love the Adirondacks. Lotta GREAT motorcycle roads up there...


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## Renovation (Dec 27, 2010)

Hi Folks,

I just thought I'd bump this thread up, since I'm making the same decision.  I'm planning on completely enclosing my pipe in an insulated chase, so it will not be visible or exposed to the elements.  I'd like to save $200 by getting galvanized instead of stainless, unless there's a compelling reason not to. 

From this thread, it seems not, which is good news for me.  But if anyone has any additional insights, I'd like to hear them.  If not, I'm content.

Thanks, and happy burning!


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## pen (Dec 27, 2010)

*This is the part of the stainless steel spec sheet from simpson*
Cost for this pipe is 172.97 from http://www.ventingdirect.com/simpso...ess-steel-class-a-chimney-pipe-length/p656032

Specifications

Material Specifications:
Outer Wall: 430 G-90 Galvanized Steel, .016" Thick, or .021" Galvalume Steel
Inner Wall: 430 Stainless, .020" Thick.
Insulation: Thermal Tech Blanket

Misc:
Maximum Temperature Rating: Rated for continuous use at 1000Â°, intermittent use at 2100Â°
Supported Fuels: Wood, Oil, and Coal
Warranty: Lifetime Warranty
UL Listed: 103HT, 103 

*Here it is for the galvanized*
The cost is 142. 70 http://www.ventingdirect.com/simpso...alvanized-class-a-chimney-pipe-length/p656033

Specifications

Material Specifications:
Outer Wall: 430 G-90 Galvanized Steel, .016" Thick, or .021" Galvalume Steel
Inner Wall: 430 Stainless, .020" Thick.
Insulation: Thermal Tech Blanket

Misc:
Maximum Temperature Rating: Rated for continuous use at 1000Â°, intermittent use at 2100Â°
Supported Fuels: Wood, Oil, and Coal
Warranty: Lifetime Warranty
UL Listed: 103HT, 103 



_Are these spec sheets wrong?  Other than the 30 dollar difference, I don't see what the heck the difference is?  This is the same spec sheet that pops up for these products on other sites as well.  I'm confused._

pen


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## Renovation (Dec 27, 2010)

pen said:
			
		

> *This is the part of the stainless steel spec sheet from simpson*
> Cost for this pipe is 172.97 from http://www.ventingdirect.com/simpso...ess-steel-class-a-chimney-pipe-length/p656032
> 
> Specifications
> ...



Hi Pen,

If you compare the sections of your citations that I've highlighted in blue with this quote from the DuraTech catalog:



> Materials and Construction:  Inner wall of 0.020" *430 stainless steel*. Outer wall options of 0.016" 430 stainless steel or 0.021" galvalume steel



You'll see the blue sections are typos, and should read "430 stainless" instead of "430 G90 Galvanized".  Then your quoted spec is consistent with the catalog, and with its own description of the stainless inner wall, which says 430 stainless, not galvanized.

The upshot seems to be, there is no difference in the specs of the galvanized and stainless pipe, except for material!  So they seem otherwise equivalent, which is a good thing for me. 

Make sense?


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## pen (Dec 27, 2010)

So the stainless pipe is stainless inside and out and the galvanized pipe is stainless only on the interior?

If so, and you don't mind the appearance, they both seem to be rated equally each with a lifetime warranty.  I guess it depends on how much aesthetics matter to you.

pen


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## Backwoods Savage (Dec 27, 2010)

Personally I could care less what my neighbors think about my chimney. It is SS up the side of the house and looks just fine. I've had galvanized before and that too looked fine. No paint.


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## chris-mcpherson (Dec 27, 2010)

I cared a little bit what a galvanized chimney would look like but in the end, the money savings meant more. I'm glad I decided to save the money because even though it's on the side of the house with the driveway... unless you mean to look at it, you don't even notice it. I have a feeling that a shiny SS chimney would have stuck out like a sore thumb.
I've also seen nothing that says galvanized MUST be painted... only tips on HOW to do it if you want to.


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## wkpoor (Dec 27, 2010)

Galvanize will rust if near smoke. My chimney cap was originally galvanize and it rusted badly. Replaced it with stainless. I'm thinking this will apply to the pipe also. Keeping it painted will probably prevent the rust but will add a maintanence aspect. Depending on how diffecult it is to access would affect my decision.


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## firefighterjake (Dec 27, 2010)

chris-mcpherson said:
			
		

> I cared a little bit what a galvanized chimney would look like but in the end, the money savings meant more. I'm glad I decided to save the money because even though it's on the side of the house with the driveway... unless you mean to look at it, you don't even notice it. I have a feeling that a shiny SS chimney would have stuck out like a sore thumb.
> I've also seen nothing that says galvanized MUST be painted... only tips on HOW to do it if you want to.



I was a bit concerned about the look of the stainless steel chimney running up the side of my house . . . and it's not like I'm all about looks or keeping up with the Jones. I just thought it might look a bit odd. 

However, after having it installed I discovered that 1) you tend to forget about the look after awhile and 2) I lucked out since you can really only see the last 2-3 feet from the road due to the location of the chimney and position of my house.


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## Renovation (Dec 28, 2010)

pen said:
			
		

> So the stainless pipe is stainless inside and out and the galvanized pipe is stainless only on the interior?



Yessir, that's how it looks to me.  And, as you see, there seems no difference in performance specs, certification, etc.  

In terms of warranty, wait a half hour...

I just checked, and the warranty appears to not distinguish between galvanized and SS skin.  Interestingly, it _is_ void if the pipe is not installed by a certified professional.  I guess they saw me coming.


> If so, and you don't mind the appearance, they both seem to be rated equally each with a lifetime warranty.  I guess it depends on how much aesthetics matter to you.



Well, appearance does matter, but no one will see it.  I'm planning on going the extra yard, and  enclosing the pipe all the way to the top--even above the roof line, in an insulated chase.  I'm hoping that a straight, 8" flue, double wall stovepipe into class A, 25' total, enclosed and insulated all the way to the top would draw with a candle, let along a cool-outlet cat.  I'm doing everything I can to make a future-proof flue that will draw well enough that it should work well with any stove I care to throw under it, even one with a 6" outlet, without having the risk of smoke spillage that a 6" flue on an 8" stove would have.  (fingers crossed)

So, if I can save $200 with a galvanized rather than stainless skin I'll never see, with no performance hit, that's good!

Thanks to all for your advice.


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## oldspark (Dec 28, 2010)

If I planed on having the house for a long time I would go with the SS, sure they both offer the same protection but the galv. has a thin layer of protection so if it gets scratched some way it will rust there where as the SS will never rust no matter what. And if you decide to paint it that will add up over the years.


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## LLigetfa (Dec 28, 2010)

I've seen enough cheap class A chimneys rusted away that I would never go that route.  Forget about those supposed lifetime warranties where inferred quality is implied.  They are all about marketing.  Good luck ever getting satisfaction on a claim.


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## Renovation (Dec 28, 2010)

LLigetfa said:
			
		

> I've seen enough cheap class A chimneys rusted away that I would never go that route.  Forget about those supposed lifetime warranties where inferred quality is implied.  They are all about marketing.  Good luck ever getting satisfaction on a claim.



Hey LL,

Thanks for your insights.

Agreed on the warranty.

Have you ever seen a quality (say Simpson) galvanized Class A pipe  that's enclosed rust away?


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## tiber (Dec 28, 2010)

> Have you ever seen a quality (say Simpson) galvanized Class A pipe  that's enclosed rust away?



(Real Life Disclosure - I work for a large construction company)...

If you want the shortest possible answer: Simpson uses hot-dip galvanization, which means it cannot possibly rust unless you puncture the pipe. 

Oh boy. This opinion I think comes from a misunderstanding of metalurgy. The galvanized pipe is less likely to rust out than stainless. It's entirely counterintuitive. Galvanization works by dipping the steel in zinc, which chemically bonds it to the steel. The metals are hot enough there's actually a layer of steel-zinc co-mingled. Stainless steel is dipped in chrome (yes the same stuff on your car), but because of the properties of chrome its simply on there and not chemically bonded. What happens is light dings and scratches don't cause the chrome layer to be hurt, but when you get under the chrome layer is when the steel can rust and bubble up the chrome layer. This is very similar to the bubbling on a chromed car bumper. Normal wear and tear is called galling. For a chimney this chrome isn't pure chrome, it's usually chrome alloy of some kind. It's entirely serviceable. The empire state building, for example, is stainless. The portland arch is aslo stainless. They have to polish the empire state building because the chrome alloy doesn't deal with acid rain too well, but the portland arch they just let hang out. Like galvanization, big chimney pipe companies know wood smoke tends to be acidic and make their stainless steel to deal with it.

But, you're talking a process that takes 20 years. This is aggrevated in a low oxygen environment where the chrome is forced to give up oxygen it's absorbed and so in a hot, dry, airless environment (a lot like a chimney, actually) you can force the chrome to burn off or change it's PH enough to attack the steel. Short of a chimney fire, this isn't going to happen, but this is why chimney fires are so bad for chimneys. Inside the chimney doesn't matter as much because it's expected to be reasonably dry (no surface water). The outside of the chimney, not so much. This is why chimney pipe erosion usually starts at the top. 

Galvanization is where things get weird. Galvanized chimneys from decent brands are almost all hot dip, which is what co-mingles the metals. You can actually electroplate it, and I think this is where the really cheap galvanized stuff got a bad name. Electroplating is worse than chroming because a piece might be galvanized, but the layer is so thin it's a joke. Furthermore you can subject metal to blackening where galvanization is actually semi porous and it's filled with oil. A little oil on a chimeny pipe is OK, it prevents it from getting dull in shipping. If it almost slips out of your hands or it has a sheen from the oil, it's too much and this is a sign that something was blackened rather than hot dipped. If you want an example of this, a lot of construction materials are actually blackened so that when you screw something together, the oil eventually wears off and the parts anneal themselves together from contact. 

Now, knowing all that happy horse crap, put a 1ft section of pipe at the top of your chimney system and keep an eye on it. When the chimney starts to erode, just replace the 1ft pipe piece to keep the smoke away from the much more expensive 4ft ones. 

*EDIT:* Before someone asks the obvious: Why is the inside of a chimney stainless rather than galvanized - The stainless surface is a lot, lot smoother which makes it easier to clean. The chrome process is expensive, which is why chrome pipes cost more. However, the chrome inside of a chimney isn't likely to die any time soon because there's nothing in there which could damage the chrome unless you're using a really, really aggressive brush.


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## PJF1313 (Dec 28, 2010)

Tiber - 

  Thanks alot for the metalurgy education!
Also, a great tip by using a 1 foot scrificial piece at the last section.


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## pen (Dec 28, 2010)

I'm surprised to hear that stainless is dipped in chrome.  I always assumed the chrome was just part of the alloy mix.

pen


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## LLigetfa (Dec 29, 2010)

tiber said:
			
		

> (Real Life Disclosure - I work for a large construction company)...


I've worked in construction and heard more than my share of bull.  I have to call BS on this one.

There are of course, many different grades of stainless.  Try holding a magnet to some stainless steel.  On some grades, you will feel a bit of pull.  On others you won't.


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## tiber (Dec 29, 2010)

LLigetfa said:
			
		

> tiber said:
> 
> 
> 
> ...



That's due to what's been galvanized or chromed. Chrome itself is nonferrous. You can chrome dip iron bars if you want.

Anyway don't take my word for it: http://www.simpsonmfg.com/docs/AnnualReport2006.pdf

Simpson sells their "Laser cut hot dip galvanizing" in the 2006 report.


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## oldspark (Dec 29, 2010)

LLigetfa said:
			
		

> tiber said:
> 
> 
> 
> ...


 +1 I worked in a meat processing plant for 29 years and no way is glav. in any way shape or form better than SS!


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## Renovation (Dec 29, 2010)

Wow, neat thread guys.

Here's what I found out about the two materials:

From http://chemistry.about.com/cs/metalsandalloys/a/aa071201a.htm



> What Is Stainless Steel and Why Is it Stainless?
> 
> In 1913, English metallurgist Harry Brearly, working on a project to improve rifle barrels, accidentally discovered that adding chromium to low carbon steel gives it stain resistance. In addition to iron, carbon, and chromium, modern stainless steel may also contain other elements, such as nickel, niobium, molybdenum, and titanium. Nickel, molybdenum, niobium, and chromium enhance the corrosion resistance of stainless steel. It is the addition of a minimum of 12% chromium to the steel that makes it resist rust, or stain 'less' than other types of steel. The chromium in the steel combines with oxygen in the atmosphere to form a thin, invisible layer of chrome-containing oxide, called the passive film. The sizes of chromium atoms and their oxides are similar, so they pack neatly together on the surface of the metal, forming a stable layer only a few atoms thick. If the metal is cut or scratched and the passive film is disrupted, more oxide will quickly form and recover the exposed surface, protecting it from oxidative corrosion. (Iron, on the other hand, rusts quickly because atomic iron is much smaller than its oxide, so the oxide forms a loose rather than tightly-packed layer and flakes away.) The passive film requires oxygen to self-repair, so stainless steels have poor corrosion resistance in low-oxygen and poor circulation environments. In seawater, chlorides from the salt will attack and destroy the passive film more quickly than it can be repaired in a low oxygen environment.



So according to this source, the stainless quality goes all the way through, and the material self-heals from scratches, which is my experience.

Now, on to galvanized steel:

From Wikipedia, http://en.wikipedia.org/wiki/Galvanization :



> Metal protection
> 
> In current use, the term refers to the coating of steel or iron with zinc. This is done to prevent galvanic corrosion (specifically rusting) of the ferrous item. The value of galvanizing stems from the relative corrosion resistance of zinc, which, under most service conditions, is considerably less than those of iron and steel. The effect of this is that the zinc is consumed first as a sacrificial anode, so that it cathodically protects exposed steel. This means that in case of scratches through the zinc coating, the exposed steel will be cathodically protected by the surrounding zinc coating, unlike an item which is painted with no prior galvanizing, where a scratched surface would rust. Furthermore, galvanizing for protection of iron and steel is favored because of its low cost, the ease of application, and the extended maintenance-free service that it provides.



So, as we all knew, galvanization is a surface coating of zinc, and more vulnerable, but the zinc will protect the steel from corroding if the coating is breached.

And another little tidbit--From http://www.finishing.com/108/38.shtml :



> Can you please let me know if there is any statistical information as to the durability & life span or structural astuteness of G60 galvanized steel.
> 
> Thanks,
> 
> ...



Now we know what the "G90" spec for the Simpson galvanized pipe means!   :coolsmirk:

So it looks like galvanized steel is not as durable as stainless, but durable in exposed applications.  Since I'm installing mine in a chase, I feel pretty good so far about going with galvanized, and spending my money on quality elsewhere.


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## oldspark (Dec 29, 2010)

pen said:
			
		

> I'm surprised to hear that stainless is dipped in chrome.  I always assumed the chrome was just part of the alloy mix.
> 
> pen


I am not sure where the idea of it being dipped came from but SS in not dipped.


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## Troutchaser (Dec 29, 2010)

I don't want anything to do with this SS and galvanized-which is better- issue, but just thought I'd add this:

I got galvanized (stainless interior) pipe and painted it black with a $12 can of BBQ paint, which will be enough for years to come should I need it.
After one year, the paint looks as good as the day it went on.


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