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View Full Version : Is it Really - Black "Iron" Pipe



Bob La Londe
05-05-2018, 01:02 PM
I'm pretty sure its low C steel, but I thought I'd ask. If I wander over to the local box store and pick up a piece of black "iron" pipe is it really iron or is it low C steel? It bends more like steel.

wombat2go
05-05-2018, 01:33 PM
https://www.astm.org/Standards/A53.htm

wmgeorge
05-05-2018, 01:35 PM
Its steel.

J Tiers
05-05-2018, 01:38 PM
Low C steel is still 99.8% or so iron......

Does it really matter? Nobody makes wrought iron pipe for general sale AFAIK.

Bob La Londe
05-05-2018, 01:54 PM
Low C steel is still 99.8% or so iron......

Does it really matter? Nobody makes wrought iron pipe for general sale AFAIK.

Weldability.

J Tiers
05-05-2018, 01:58 PM
It's welded to make it, so that should be a given......

Jim Stewart
05-05-2018, 02:13 PM
I've welded 3/4" and 1" black iron pipe. No problem.

-js

Willy
05-05-2018, 02:37 PM
Yup, "black iron" pipe takes to welding very nicely.
I believe that it is probably the go-to source of of tubing for many amateur welding projects due to it's availability at every hardware store. Used within it's limitations it's great for non-critical applications.

metalmagpie
05-05-2018, 07:31 PM
YMMV. When I buy black "iron" pipe, what I get is painted black. What I really want, which is really hard to find, is bare pipe.

metalmagpie

loose nut
05-05-2018, 07:33 PM
The name is a hold over to days gone by. Probably "malleable iron" or "wrought iron" pipe at one time hence the name.

CCWKen
05-05-2018, 08:21 PM
YMMV. When I buy black "iron" pipe, what I get is painted black. What I really want, which is really hard to find, is bare pipe.

metalmagpie
The only time I've seen that is with nipples. Pipe around here is either painted black or galvanized.

reggie_obe
05-05-2018, 08:29 PM
YMMV. When I buy black "iron" pipe, what I get is painted black. What I really want, which is really hard to find, is bare pipe.

metalmagpie

Is they didn't paint it, by the time it's made the long voyage from the sub-continent, it would be all rusty outside.

3 Phase Lightbulb
05-05-2018, 08:29 PM
I bought lots of bare SCH40 pipe from a steel supplier. Before I got the bare stuff I used Home Depot SCH40 "black iron" pipe and it was absolutely wonderful to work with. It machined very well when I was notching it and it welded really well. The only problem with it is that black anti-corrosive coating needs to be removed but other than that, it smells and tastes like mild steel.

lugnut
05-05-2018, 09:17 PM
The true test is to trying to bend it with a elcheapo Harbor Fright bender. True pipe will bend, the other will just pull apart. Been there done that.

3 Phase Lightbulb
05-05-2018, 10:12 PM
The true test is to trying to bend it with a elcheapo Harbor Fright bender. True pipe will bend, the other will just pull apart. Been there done that.

The home depot black iron pipe I used would also bend very nicely with the HF pipe bender. It bends really well with the HF bender. I made this minibike with Home depot black iron pipe and a HF pipe bender:

http://www.bbssystem.com/pictures/minibike/mini4.jpg

http://www.bbssystem.com/pictures/minibike/mb6.jpg

metalmagpie
05-05-2018, 10:18 PM
The home depot black iron pipe I used would also bend very nicely with the HF pipe bender. It bends really well with the HF bender. I made this minibike with Home depot black iron pipe and a HF pipe bender:

http://www.bbssystem.com/pictures/minibike/mini4.jpg

http://www.bbssystem.com/pictures/minibike/mb6.jpg

First minibike I've seen with a snowplow attachment!

rws
05-06-2018, 03:53 AM
In the construction industry, black iron pipe is used for chilled and hot water distribution lines. Usually 2" and down are threaed, over that is welded. However, some applications call for all welded lines like for fuel, so even 3/4" lines are welded using "socket" fittings.

Hardware stores and the like call it "gas" pipe.

3 Phase Lightbulb
05-06-2018, 11:30 AM
In the construction industry, black iron pipe is used for chilled and hot water distribution lines. Usually 2" and down are threaed, over that is welded. However, some applications call for all welded lines like for fuel, so even 3/4" lines are welded using "socket" fittings.

Hardware stores and the like call it "gas" pipe.

Does steel pipe build up some type of scale or protective layer that prevents corrosion beyond internal surface corrosion? I would think black iron pipe (mild steel) would just rust through from the inside out if used for water applications? It's great for gas and provides excellent physical protection from someone driving nails into walls, or cutting into walls, etc.

J Tiers
05-06-2018, 11:41 AM
Usually there is hard water deposit that builds up faster than the corrosion. Corrosion (oxidation, rust) needs oxygen, and there is only the free oxygen that comes in with the water. Nothing like sitting out in the weather.

Cast iron pipe was used for drains.... and in that service was wet and then exposed to air, alternately. It would last for 80 years.... at least ours did, we only had it re-lined a few years ago and the house is from the 30's.

wmgeorge
05-06-2018, 01:33 PM
Does steel pipe build up some type of scale or protective layer that prevents corrosion beyond internal surface corrosion? I would think black iron pipe (mild steel) would just rust through from the inside out if used for water applications? It's great for gas and provides excellent physical protection from someone driving nails into walls, or cutting into walls, etc.
For city water lines or water lines for drinking water its galvanized pipe. For CW, HW and Steam the boiler or water treatment usually keeps it from rusting on the inside. Once you get all the "free" oxygen out of the water, usually by heating to a certain temperature the rust issue goes away, in a closed loop system. Of course black pipe is also used for natural gas and air lines also. Rumor is the galvanized comes off and clogs strainers and valves. Kind of an old wife's tale. I think copper and galvanized can be used for natural gas, but tradition gets in the way!

rws
05-06-2018, 02:34 PM
I have rarely seen galvanized specd for gas, but sometimes it is. Copper is used for gas with flare fittings. These flex lines used now are soft copper, kind of like cheating since there is no skill to make them up. Funny gas pipe can be welded black iron, but you don't solder copper gas pipe.

wmgeorge
05-06-2018, 05:32 PM
I have rarely seen galvanized specd for gas, but sometimes it is. Copper is used for gas with flare fittings. These flex lines used now are soft copper, kind of like cheating since there is no skill to make them up. Funny gas pipe can be welded black iron, but you don't solder copper gas pipe.

Tradition says and more than likely its not true that natural gas contains sulfur or perhaps coal gas is mixed with it, and copper or galvanized pipe can react to it. I am pretty sure in Europe they use copper pipes like we do for water to supply natural gas? As a pipefitter I have silver brazed copper pipe for medical gases.
The worst stuff I have seen used is that flexible gas line, very thin stainless steel corrugated pipe covered with a yellow PVC cover. Installed correctly and to Code its safe, but otherwise its a disaster. Its used behind walls and in ceilings or crawl spaces, people drill or drive nails and bingo its a major fire!

J Tiers
05-07-2018, 12:26 AM
....
The worst stuff I have seen used is that flexible gas line, very thin stainless steel corrugated pipe covered with a yellow PVC cover. Installed correctly and to Code its safe, but otherwise its a disaster. Its used behind walls and in ceilings or crawl spaces, people drill or drive nails and bingo its a major fire!

That stuff is only ever intended for use behind an appliance that may need to be shifted sometimes, or to make the connection more easily. I do not like it, but it gets used. Trying to get iron pipe cut and threaded to line up exactly with an appliance connection in a tight space is a real hassle.

reggie_obe
05-07-2018, 06:55 AM
That stuff is only ever intended for use behind an appliance that may need to be shifted sometimes, or to make the connection more easily. I do not like it, but it gets used. Trying to get iron pipe cut and threaded to line up exactly with an appliance connection in a tight space is a real hassle.

No. What wmgeorge is referring to is this: https://www.homedepot.com/p/1-2-in-x-25-ft-CSST-Corrugated-Stainless-Steel-Tubing-11-00525/203073939
Intended to replace threaded pipe in walls and under floors, not flex-line used as an appliance service connection. Major problem with its is "certification". The only training the manufacturer requires is that the purchaser read the supplied, free instruction manual and fill out the registration card in the back.

wmgeorge
05-07-2018, 09:38 AM
No. What wmgeorge is referring to is this: https://www.homedepot.com/p/1-2-in-x-25-ft-CSST-Corrugated-Stainless-Steel-Tubing-11-00525/203073939
Intended to replace threaded pipe in walls and under floors, not flex-line used as an appliance service connection. Major problem with its is "certification". The only training the manufacturer requires is that the purchaser read the supplied, free instruction manual and fill out the registration card in the back.

Correct. Its like Romex for the home owner. I can only imagine the fires that will result from Joe Six Pack doing his own gas piping.

J Tiers
05-07-2018, 10:09 AM
Sheesh.... didn't know about that stuff.

I sure would not use it.

Bob La Londe
05-07-2018, 10:11 AM
Correct. Its like Romex for the home owner. I can only imagine the fires that will result from Joe Six Pack doing his own gas piping.

Safety plates are your friend.

reggie_obe
05-07-2018, 10:26 AM
Safety plates are your friend.

Correct! ...and to be used when running PEX through a sill plate or stud as well. But will Joe Homeowner spend the extra cost, no.

J Tiers
05-07-2018, 03:40 PM
Correct! ...and to be used when running PEX through a sill plate or stud as well. But will Joe Homeowner spend the extra cost, no.

Plumbers and electricians do not use them either, in many cases....

Ries
05-07-2018, 04:34 PM
The last mill making real wrought iron pipe was in Scandinavia, Sweden, I think, and it closed in the early 70s. Real wrought iron pipe was used in corrosive and some petrochemical applications, and was replaced by stainless steel and other high tech alloys like monel and inconel in those applications in the sixties.
So, originally, there was wrought iron pipe.
And you still come across cast iron pipe sometimes, which is still made in the USA for drain and sewer applications.

JoeLee
05-07-2018, 10:59 PM
YMMV. When I buy black "iron" pipe, what I get is painted black. What I really want, which is really hard to find, is bare pipe.

metalmagpieI haven't seen any bare steel pipe since I was a kid. It's either black paint or galvanized.

JL...................

3 Phase Lightbulb
05-07-2018, 11:03 PM
I haven't seen any bare steel pipe since I was a kid. It's either black paint or galvanized.

JL...................

Steel suppliers sell it. It's just SCH40 steel pipe. I bought 100's off feet of it years ago in 3/4" and 1/2" sizes. Here is a link to one supplier:

https://www.metalsdepot.com/steel-products/steel-pipe