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Black Iron Pipe vs. Carbon Steel Pipe

08/16/2007 9:12 AM

What is the difference between black iron pipe and carbon steel pipe, or are there any?

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#1

Re: Black iron pipe

08/16/2007 9:42 AM

Sure are. Black iron pipe is cast from several grades of ductile or malleable iron whereas carbon steel pipe is generally wrought welded or seamless. Cast iron pipe is used for underground or submerged applications and for main steam pipes and branches that are subjected to acids. It was also common to use cast iron pipe and fittings for municipal cold water lines 4" diameter and above. Commercial cast iron pipe is unsuitable for lines subjected to expansion strains, contractions, and vibration unless the pipe is very heavy. It is not suitable for superheated steam or for temperatures above 575 degrees F. Cast iron pipe in underground applications (such as sewer lines) usually has bell and spigot ends whereas exposed pipe usually has flanged ends.

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#2
In reply to #1

Re: Black iron pipe

08/16/2007 9:49 AM

Good reply.

Ductile or malleable iron [DMI] can be used for potable water supply whereas carbon steel [CS] cannot; it rusts from within and sheds particles. DMI cannot be welded whereas CS can be. DMI cannot be threaded whereas CI can be; different horses for different courses.

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Nerdy.

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#3

Re: Black Iron Pipe vs. Carbon Steel Pipe

08/17/2007 2:05 AM

If you go to Home Depot and ask for schedule 40 (or 80) "black iron" pipe, you will get steel pipe, easily threaded and welded. Galvanized schedule 40 (or 80) pipe is the same stuff, but galvanized, of course, so you wouldn't want to weld it.

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#5
In reply to #3

Re: Black Iron Pipe vs. Carbon Steel Pipe

08/17/2007 8:25 AM

I know you can use black pipe for natural gas lines, but at Home Depot they told me I could not use the galvanized pipe for gas.

What is the "black" part of the black pipe. What is the coating or treatment?

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#7
In reply to #5

Re: Black Iron Pipe vs. Carbon Steel Pipe

08/17/2007 8:50 AM

I'd always assumed the black coating was carbonized oil (as on a black iron frying pan) but I read recently that it is simply lacquer.

Apparently, the problem with galvanized pipe for gas plumbing is that particles or flakes of zinc can get into valve orifices, etc. I'd think little particles of rust or lacquer would do the same, but evidently not.

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#13
In reply to #5

Re: Black Iron Pipe vs. Carbon Steel Pipe

08/18/2007 8:27 PM

The real reason you could not use galvanized pipe was the sulfur content of the gas. this is not necessary true today because most (all?) natural gas goes through a sulfur recovery unit before you receive it.

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#22
In reply to #5

Re: Black Iron Pipe vs. Carbon Steel Pipe

03/09/2010 3:11 PM

Galvanized pipe is perfectly fine to be used for natural gas systems. Is an approved material per Uniform Plumbing Code but check your local Administrative Authority...

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#23
In reply to #22

Re: Black Iron Pipe vs. Carbon Steel Pipe

04/18/2010 6:24 PM

The galvanized ban as back hen they did not remove the Sulfar and there was a chemical reaction deteriorating the galvanized pipe!

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#4

Re: Black Iron Pipe vs. Carbon Steel Pipe

08/17/2007 3:17 AM

this is as simple as the difference between Iron and Steel.

Iron has a higher carbon content so that it is Austenitic with cementite (not sure on the translations) and free carbon on the cristal border.

Steel is ferritic.

Of coarse the dealer may call a black steel pipe an iron pipe where he calls the galvanised version steel.

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#6

Re: Black Iron Pipe vs. Carbon Steel Pipe

08/17/2007 8:29 AM

In the pipe fitting world in the USA black iron is a slang name usually used to describe threaded sch.. 40, SA 53 ERW pipe. This would typically be used for systems below 150 lb. psi Although one would probably use cast iron or malleable fittings the pipe is made of steel. There is no difference in SA 53 pipe whether it is called black iron or not and whether it is beveled and welded or threaded.

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#8
In reply to #6

Re: Black Iron Pipe vs. Carbon Steel Pipe

08/17/2007 10:08 AM

There is a difference between black iron pipe and black steel pipe. Black steel pipe, as used for natural gas lines, for example simply means unplated steel pipe.

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#9

Re: Black Iron Pipe vs. Carbon Steel Pipe

08/17/2007 11:18 AM

As the term is commonly used in the USA, black iron pipe is just steel pipe which comes painted black. You can buy iron pipe, commonly used for plumbing due to its corrosion resistance, but if you order black iron pipe it will be steel pipe.

I don't know why it is referred to as "iron", but then hamburgers do not have any ham in them, gasoline is a liquid...

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#10
In reply to #9

Re: Black Iron Pipe vs. Carbon Steel Pipe

08/17/2007 1:40 PM

I don't know why it is referred to as "iron", but then hamburgers do not have any ham in them, gasoline is a liquid...

...and "iron workers" actually work with steel 99% of the time, and "wrougt iron" is typically steel, as are "tire irons".

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#11

Re: Black Iron Pipe vs. Carbon Steel Pipe

08/17/2007 11:35 PM

In addition to all the above you can join black pipe (threaded) with threaded copper adaptors directly whereas you cannot join galvanized pipe and copper. That will corrode unless you use special connectors. I'm forgetting what they call them. They are inert so you don't get the corrosion. I'm sure someone else can help with the name. They sell them in the plumbing supply houses. I've never seen them in home depot.

In fact you shouldn't even mix black and galvanized in the same runs. Give them enough time and they will corrode and leak at the joints. They didn't know that when they ran the gas lines in my house and mixed in a few galvanized fittings about a hundred years ago. Or they knew but figured they would be dead and buried by the time the pipes started leaking. I had to run all new black pipe.

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#12
In reply to #11

Re: Black Iron Pipe vs. Carbon Steel Pipe

08/18/2007 10:05 AM

The special connectors are dielectric unions.

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#14
In reply to #12

Re: Black Iron Pipe vs. Carbon Steel Pipe

08/18/2007 9:56 PM

Ive been in the business 17 years(industrial fabrication) and i have heard the term black iron used a lot to describe cheap steel pipe used primarily for plumbing. Threaded, welded and coupled. Its steel... they do make a cast iron pipe but its not commonly used for anything above ground anymore and rarely used at all. The term Black iron comes from an oil applied as a protective coating while the pipes still hot. It makes it black and leaves a rough feel kinda like old cast iron .I believe that was mentioned already though.

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#31
In reply to #12

Re: Black Iron Pipe vs. Carbon Steel Pipe

10/08/2010 1:08 PM

Dielectric unions are as they discribed - no electrical connection between the two pipes. Typical unions are ground joints.

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Anonymous Poster
#15
In reply to #11

Re: Black Iron Pipe vs. Carbon Steel Pipe

08/22/2007 5:19 PM

I'm working on chilled water i have to put on test for 8hrs at 400lbs every thing holds pressure but black iron thread to copper thread heard black iron to brass and brass to copper works but do u know why black iron to copper leaks

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#16
In reply to #15

Re: Black Iron Pipe vs. Carbon Steel Pipe

08/22/2007 7:13 PM

It seems it would have to be due to the placement on the galvanic series. Brass (yellow, naval, and red) is between copper and steel. Therefore the corrosion potential is less between brass and either of the other two, than from copper to steel. That problem shouldn't show up in a few hours, though. Were these newly assembled pipes that leak?

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#17
In reply to #16

Re: Black Iron Pipe vs. Carbon Steel Pipe

08/26/2007 4:45 PM

yes every thine was new

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Anonymous Poster
#18
In reply to #11

Re: Black Iron Pipe vs. Carbon Steel Pipe

04/05/2009 6:47 AM

Galvanic action between two dissimilar metals in the presence of water

Benjamin

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#19

Re: Black Iron Pipe vs. Carbon Steel Pipe

05/17/2009 9:40 PM

Would iron pipe be good enough steel to make wood lathe chisels? Would it hold a good edge if I heated it and quenched it? Is there an inexpensive source for 1/4 inch thick HSS?

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#21
In reply to #19

Re: Black Iron Pipe vs. Carbon Steel Pipe

11/23/2009 7:46 PM

Wood is softer then steel so you could use it but it would be poor quality to sharpen and it will bend easely.

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#20

Re: Black Iron Pipe vs. Carbon Steel Pipe

11/23/2009 7:30 PM

Black iron pipe is an old term for black pipe. Back when they first came out with pipe it was a very crude steel/iron mixture. They improved the process to steel pipe. The difference between iron and steel is all to evident. steel bends and iron does not. You can cut steel with a torch - iron you can not. Iron is casted - steel is manufactured, formed and casted in many forms/objects such as (tin) sheet metal, nails, screws, brackets, eating utensils, fry pans,cars-frames tools. metal buildings, pipe etc.etc. Pipe (crude)and galvanized use to be used for water, drains, petrolium products (oils-fuels etc.etc.) and gas (manufactured & natural), boilers, steam etc.etc. Today "black pipe" is still use for every thing but fresh water. Galvanize pipe is hardly used for fresh water any more because rusts and rots at the threads. Galvanized conduit (emt & rigid) is use in electrical sevices and underground to protect the wire but it has different characteristics. Typical black pipe is very low carbon content to resist rusting. There is higher carbon content steel pipe (also tubing)for typically higher pressures uses. What is most common is the low carbon steel blackpipe. which is after all of this is the same as (the old term) black iron pipe.

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#24

Re: Black Iron Pipe vs. Carbon Steel Pipe

05/19/2010 12:07 AM

This is all great input. Thank you. Code requirements aside, does anyone know what sort of longevity I can expect out of the standard "black steel pipe" that is sold at Home Depot or Lowe's in an underground natural gas application between a gas meter and a backyard grill? As previous posts have mentioned, this is basically just steel pipe that has a black varnish on it but is not coated with anything extraordinary. I believe this is the same pipe that is typically used inside of a house. I'd really like to use this for an outdoor application and would consider wrapping all 40' of it with special tape, or using anode bags, if there is a risk that this pipe would rust through in an unreasonable amount of time. Does anyone have experience using the black steel pipe sold at Lowe's or Home Depot in underground applications? If so, any thoughts on how good it will hold up? Thank you.

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Anonymous Poster
#25
In reply to #24

Re: Black Iron Pipe vs. Carbon Steel Pipe

06/17/2010 6:20 PM

If you are going to make a run of gas line, the simplest, most efficient, and safest thing to do is to buy pipe specially coated for underground burial, usually with a thick green coating, in my experience. Then, after making all threaded connections, coat any nicks or marks with a brush-on repair coating available where you buy the coated pipe. Also, be certain to coat all connections. Where the pipe is exposed at the riser, wrap it with protective tape, which is heavy mill plastic with a good mastic, and made especially for this purpose. When laying the pipe in the ground, be certain to level the bottom of the trench so that the pipe is evenly supported along its length. Remove all rocks, especially larger and sharped edged ones, from both the trench bottom and the fill dirt. It is even better to use tamped sifted dirt or sand on the trench bottom, and sifted dirt for the fill. Also, after the pipe is installed, and before filling the trench, pressure check the new installation to the above-ground connection point with pressurized nitrogen (doesn't change pressures significantly with temperatures). You do this on a sealed system, with attached gauge, at a set pressure, over a period of several hours. If the pressures stays the same, you have no leaks. If it drops, then you must find and repair the leak. All the above may be required by some code-enforcing agency, but the real reason you want to do it is for the safety of you, your family, and others in the vicinity. Natural gas isn't pooling as is LPG, and contains significantly less energy per cubic foot, so isn't so terribly explosive as LPG, but it still is nothing to be careless with. If you make a gas installation in your back yard to any lesser standard, you are not being frugal, but only foolish. Take it form an old man who has learned many things the hard way.

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#26

Re: Black Iron Pipe vs. Carbon Steel Pipe

10/07/2010 2:42 PM

So I am having a new house built and they used "black iron pipe" for the gas lines in the house, but at all connections or 90 degree turns they used what appears to be regular galvenized connectors. Will this casue a problem? i.e. should even the connectors and 90 degree turns be black iron as well?

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#27
In reply to #26

Re: Black Iron Pipe vs. Carbon Steel Pipe

10/07/2010 2:50 PM

Galvanize is better, so I wouldn't worry about it. There is a theory that some cheap galvanizing will cause flakes to build up in the line, which is why they have sediment traps at the inlet of all appliances. Your building code will mandate these sediment traps, and you won't pass inspection without them. But to answer your question, no don't worry about the galvanized fittings. They are higher quality than the black iron pipe. If you look outside at your gas meter, you will see you also have galvanize pipe outdoors....Most builders just use black iron pipe indoors since it is cheaper than galvanized pipe.

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#28
In reply to #27

Re: Black Iron Pipe vs. Carbon Steel Pipe

10/08/2010 4:04 AM

I really question your explication: this is concerning a gas distribution network in a house.

As explained earlier: you should not mix galvanised with black and certainly not mix galvanised with brass.

But as the pipe will not contain water, the risk for corrosion is low.

When the inspection prior to releasing the line did not make any comment, there will be no legal issue. If it still needs to happen, make sure that you point their attention on it.

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#29
In reply to #28

Re: Black Iron Pipe vs. Carbon Steel Pipe

10/08/2010 9:08 AM

In the US, it is perfectly ok to use galvanize outside and black iron inside as long as there is a dielectric union between the 2 because they are dissimilar metals. This is done all the time.

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#32
In reply to #29

Re: Black Iron Pipe vs. Carbon Steel Pipe

10/08/2010 5:55 PM

Both pipes is still steel no dissimilar metal - only one is coated with zinc - don't understand where you heard about dielectric union between the two. disimilar metal which have reactions to each other are ferrous and nonfarrous --

dis·sim·i·lar -- [dih-sim-uh-ler, dis-sim-] –adjective

not similar; unlike; different. Origin: 1615–25; dis-1 + similar

fer·rous --Spelled[fer-uh s] --–adjective Chemistry . of or containing iron, esp. in the bivalent state.

Origin: 1860–65; < L ferr ( um ) iron + -ous

non·fer·rous [non-fer-uhs] –adjective

1. (of a metal) containing little or no iron. 2. noting or pertaining to metals other than iron or steel.

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Anonymous Poster
#30
In reply to #26

Re: Black Iron Pipe vs. Carbon Steel Pipe

10/08/2010 1:02 PM

Yes they should. The gas utilities frown on galvinized (some will not allow it) because they found that the galvinize breaks down inside (chafes) from the chemicals in the gas (nat/propane) and contaminates (over time) the appliance gas valves to malfuction. A couple of fittings is low for contamination but it's there. It's what they probably had on hand cause the fitting are more expensive then black. The only place I can think of at the moment where galvinized is use a lot when the pipeing for liquid petrolium products but the threads are still exposed outside. From my point of view galvinize fittings should be discontinued. The deteriate at the threads most times cause there not coated. Your suppost to use brass/copper/plastic for water anyways.

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