HOME / sitemapFAQsBOOKSHelp WantedsAdvertiseContact   you are here: Hotline/Forum => Letter 31203
most fun in metal finishing

What is black iron?


Q. Can anyone explain to me, what is Black Iron and what is the chemical composition of black iron, please?

Vinu Varughese
water utility - Philadelphia, Pennsylvania


A. Hi, Vinu. It is not possible to say what a term like "black iron" means out of context because it is not a specification but merely slang used as a shortcut. But because you are with a water utility, I'll assume you are referring to "black iron pipe". In this context, 'black iron' is just slang referring to steel pipe with black paint on it or no paint on it as opposed to being galvanized.

As the son of a plumber from before the age of plastic pipe, "black iron" was used on gas pipes (and often still is), whereas galvanized piping was used on waste piping.

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey


A. It is my understanding that black iron is also called "black rust" as opposed to red rust. The black rust is much less "fluffy" than red rust. That is, red rust will allow oxygen and moisture to permeate to the surface and allows the progression of corrosion. The black rust is a protective oxide layer that helps block any progressive corrosion. This is sometimes referred to as a conversion coat. The black rust is ferrous oxide whereas the red rust is ferric oxide.

William Calvert
- York, Nebraska

June 30, 2008

A. The context I heard it in is the manufacture of ferrous sulfate. We were looking at potential markets for it.

Thomas Vinson
- Austin Texas

December 28, 2011

A. I've seen the term 'black iron' for cookware at
They refer to 'deep spun cold roll steel' as black iron.
Maybe that's of help to you?

Kelly Dee
- Auckland, New Zealand

June 29, 2011

Q. In the context of horse bits, what base material does one use to make a mouth piece that develops "black rust" (aka patina?) rather than red rust? Do I need a special steel alloy that is somehow further processed?

Andy Dearmont
hobbyist - Lincoln Nebraska


Q. I am researching pipe to be used in boiler exhausts. I what to know if Black Iron Pipe or Galvanized Iron Pipe works best in exhaust pipe? Hope you consider my inquiry.


A. I've seen both used, Richard, and they both seem okay. I'd guess that a high temperature paintamazoninfo is better for high temperatures than galvanizing though.

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

October 29, 2009

Q. I have spent the morning looking for sheet "black iron" material with no success. As I remember it was a soft easily formed material, black in color. It was used in car body repair and is easily shaped,welded or brazed. Where can I get some? Black pipe is altogether a different material.

dean baker
dean machines - Eugene Oregon

October 30, 2009

A. Hi, Dean. I believe you are thinking of hot rolled low carbon steel sheet/plate, available from steel supply houses like Ryerson. Good luck.


pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

November 9, 2011

Q. What is black iron in the context of a 'scythe' ?

Badol Roy
- Dhaka, Bangladesh

October 3, 2008

Q. I was actually wondering if there was a metallic alloy or compound referred to as black iron or if it may have a nickname for a metallic element?

Sean Coleman
- Australia, Victoria, Melbourne

Black iron pipe -- same as black steel? same as spiral welded steel? same as ductile iron?


Q. What's the difference of black iron spiral welded steel pipe as compared to a spiral welded steel pipe, if any?

Charles Bryan Carame
Baguio Water District - Baguio City, Philippines


Q. What is the difference between black iron pipe and black steel pipe and their applications?

Sol Posada
- Hollywood, Florida

Steel Pipe: A Guide to Design and Installation

January 27, 2010

Q. Black iron pipe for the fire protection: what is meant by black iron pipe? What are the standards and codes for this pipe, and what is the difference between seamless and welded pipes? May I weld a seamless pipe?

ramesh kumar
piping design - al khobar, KSA

June 23, 2010

A. Black iron in the true sense really means wrought and tempered iron.

It may be in all its forms - plain wrought (as in kitchenware), faggoted iron (originally referred to as "Best", "Best Best" (for faggoted twice) and "Triple Best" (for faggoted three times).

It may be hardened or unhardened, so the term is very generic, usually to differentiate from cast iron.

The term is also erroneously used to refer to Ductile Iron or Low Carbon Steel, but it is not the same thing.


Ron Shaw
Engineering - Newcastle, United Kingdom

January 5, 2011

Q. Which is the most accurate classification (or made-of-what-material type) of a black iron pipe? Carbon steel or Mild steel?

Rosalie Taunan
ultrasonic flowmeter user - Davao City, Philippines

January 5, 2011

A. Hi, Rosalie. All three terms are slang rather than specifications, so the point may be moot anyway. But I think that I would use the term "mild steel" or "mild carbon steel" because the term "black iron" is actually inaccurate as Ron has mentioned, and some "carbon steel" is not mild whereas black iron pipe probably is mild.


pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

March 1, 2011

Q. For pipes that do not have threads, do you just call them unthreaded pipes or is there a specific term for it?

Aaron Clark
- L.A., California, USA

March 3, 2011

A. Hi, Aaron.

I believe you simply specify it as black iron pipe by size and wall thickness, like this: 2" NPS (nominal pipe size) Sch. 80 black iron pipe. But note that a 2" NPS pipe is neither 2" I.D. nor 2" O.D. :-)


pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

January 27, 2012

A. From what I found out today, there is no such thing as black iron pipe. If you call a steel house and asked for black iron pipe you get seam welded steel pipe painted black and it is hard to thread. If you go to a plumbing supplier and ask for black iron pipe you get ductile iron pipe, which is gray and easy to thread. Steel pipe can be used for some pressure application and as structural members. Black iron pipe is only for pressure not for structural. Personally I don't know how you can call steel pipe black iron, just confusing everyone.

Steven Rondeau
- Au Sable Forks, New York

January 30, 2012

Hi, Steven. You're right that steel pipe shouldn't be called iron pipe. But when people say "black iron pipe" they may mean steel pipe whether we like it or not.

At the same plumbing store, if you ask for "tin" you'll get galvanized sheet metal -- steel sheets with a coating of zinc -- no tin anywhere. If you ask for tin foil, you'll get aluminum foil. The practical answer is that you must rely on real specifications to describe what you want, rather than slang which will mean different things in different contexts.


pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

September 16, 2012

A. Actually black iron, by means of sheet, is Iron that is treated to withstand high heat. I'm not sure what type of iron it is or how it's prepared exactly, but I do know it's iron and not steel. I know this because a lot of our scrap cannot be tossed in the steel/galvanized scrap bins because the recycler will not take ferrous materials. Instead we have to take it to an all purpose recycler since we can throw the crap away in our dumpster. I work in a sheet metal shop, we use it primarily to fabricate heat exchange/exhaust ducts for AC/kitchens where stainless steel ductwork is impractical. Don't call a steel mill looking for it, call an Iron works or a metal dealer geared toward sheet metal for construction if you're looking to find this.

Jason Wright
- Pearl City, Hawaii, USA

January 22, 2013

Q. What is the grade of B.I. Pipes and G.I pipes?

Dyebhe Day
- Philippines

January 23, 2013

A. Hi Dyebhe.

With no disrespect, I don't think that's the question to ask or how to proceed. Rather, pick a standards body that you want to use, like ASTM or ISO, look up some standards for the kind of pipe you want, and check if they properly cover what you want (for example, pressure pipe vs. drain pipe, threadable vs. weldable). Maybe start with ASTM A53. You will sometimes see an ISO or ASTM stamp right on the pipe. Good luck.


pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

February 15, 2013

Q. Kindly let me know the Carbon composition of Black Iron.

Lahiru Jayasuriya
- Madampe, Sri Lanka

February 14, 2013

A. Hi Lahiru.

The way I see it, you are taking a very imprecise piece of slang, "black iron", which means many different things to different people, and trying to put a fine point on it. I don't think it's possible to answer you. Sorry, but I think it's rather like asking us to tell you how many pounds a "heavy" rock weighs? Good luck; maybe I'm wrong.


pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

April 7, 2014

A. Black iron pipe, even though thought of as steel, is called as such because steel is an alloy mix of iron & carbon. Technically, the pipes are iron because steel is simply iron w/ hardening agents (alloys) carbon being the primary alloy hardening agent. All steel is iron. Because there are several classifications of pipe (stainless, galvanized, carbon/fiber, etc.) the traditional black iron classification was maintained for simplifying purposes, as the pipe truly is black iron.

S Davis
- Auburn, Maine, USA

May 31, 2014

A. Know cast iron from steel, just always heard carbon steel referred to as black iron. Cut and thread "black iron" for gas lines

Jeremy burns
- cleveland, Tennessee

May 2014

Indeed S.; indeed Jeremy. Some readers want "black iron" to have a precise, well-defined meaning that precludes other people from using the term to describe other things, but life just doesn't work that way ...

To an infantryman, a "tank" is an armoured fighting vehicle, whereas to a fuel delivery driver a "tank" is a vessel to hold petroleum products -- and no matter how one group rants and shouts, that's the way it is. So too with "black iron".


pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

What is black steel? What's its fire rating?

October 21, 2014

Q. I came across a requirement by a mall consultant that the smoke extractor duct we proposed has to be in black steel. As standard we do provide extractor ducts in mild steel. Consultant himself couldn't explain why it's specified. So ... he wanted 2 hours fire rating for the duct as well. In terms of fire protection, is black steel better than mild steel? Or is it a wrong usage of terminology by using black steel instead of mild steel? Can black steel be used for duct manufacturing? I heard black steel is the very basic result of steel formation and untreated. Appreciate if some one could share your knowledge.

Sunil Lukose
- Dubai, Dubai, United Arab Emirates

November 2014

Hi. "Black steel" is slang, not a specification. Still, Jason W claims above that if you call an iron works or a metal dealer geared towards sheet metal, rather than a steel mill, you'll all be on the same page. Good luck.


pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

ADD a Q or A to THIS thread START a NEW THREADView This Week's HOT TOPICS



JobshopsCapital Equip. & Install'nChemicals & Consumables Consult'g, Train'g, SoftwareEnvironmental ComplianceTesting Svcs. & DevicesUsed & Surplus

©1995-2015     -    Privacy    -    Search