Black Iron?

[donf]

Frequently, I hear or see the misnomer "black iron" used to describe carbon steel pipe. Can anyone offer any insight, history or technical basis for this term?

Thank you,

Donf

 

[rnd2]

Generally associated with wrought iron

 

[metengr]

Today, carbon steel pipe supplied under ASTM A 53 is sometimes referred to as "black iron pipe" because it contains mill scale (iron oxide) from manufacturing that is left on the surface of the pipe. This pipe can also be furnished as hot-dipped galvanized.

As rnd2 stated, the original "black iron pipe" term was essentially wrought iron pipe - iron with iron silicate slag and very little carbon. Iron oxide (black color) from forming operations at elevated temperature was left on the surface of the pipe, thus enhancing corrosion resistance in certain media. Traditional wrought iron was hand worked at elevated temperatures, resulting in glassy-like iron silicate slag embedded in ferrite (iron).

For those purists, from what I remember reading, actual wrought iron is no longer manufactured (discontinued in 1969). The "wrought iron" sold today is really very low carbon steel.

 

[unclesyd]

Good old wrought iron is still made, but not in the US as far as I know. I’ve heard that some wrought or puddled iron is still made on a very small scale by some artists .

There was another iron, Charcoal Iron, that I think was the original "Black Iron" .

The general usage now for “black” is for any steel, alloy or not, that doesn't carry a specification or has no coating.
ASTM A53 Black
ASTM A193 B7 Black
ASTM A325 Black

In fact some of the codes require “black or plain fasteners” to lubricated.

Here is the real thing.

http://www.realwroughtiron.com/index.asp