Black Iron

What exactly is a "black iron" tank? Same as a steel tank or..?

I was crawling through a new-build (well, 2015) DeFever the other week and noted the fuel tanks were placarded as being black iron.

Yes, it means steel. Black iron is slang term and generally designates steel with no coating or a shop coating of black paint as opposed to galvanized. Like black iron water pipe.


David

djmarchand said:

Yes, it means steel. Black iron is slang term and generally designates steel with no coating or a shop coating of black paint as opposed to galvanized. Like black iron water pipe.


David

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I don't believe it's called black iron due to any paint on the surface but due to the the thin layer of oxidized iron that forms on the surface during the manufacturing process.

"One advantage of black carbon steel is the natural anti-corrosion property of the black iron oxide coating, because the oxide acts as a barrier to keep oxygen from the iron below. The thin oxide layer is created at high temperatures, forming a durable layer requiring no further treatment or coating."

It's also a very easy steel to weld.

Black Iron is NOT steel, it does not have the alloys that make Iron into steel

mramoo said:

Black Iron is NOT steel, it does not have the alloys that make Iron into steel

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I beg to differ.

Producing pig iron is the first step towards making steel. It is iron ore that has been reduced in a blast furnace to remove the oxygen in the Fe2O3 ore to make iron. Pig iron can be used directly as cast iron or it can be further processed to make steel. It has 1-3 percent carbon left over from the reduction process which makes it brittle and non malleable/weldable, but is fine for engine castings among other things.

Generic steel, ie black iron, really doesn't have any alloys added. It is just pig iron which has had the carbon oxidized out to get the carbon down to less than a percent.

Some pipe, rebar, low strength structural members and other low strength items are made from this generic steel that some people call black iron. Adding alloys in the carbon oxidation step does add strength, anti corrosion and other useful properties. These are the familiar 4140 and similar alloys.

A simple test- if it can be welded, it is steel.

David

Steel must have less than 2% carbon, Black iron has more than 2%. they are two different alloys

Well, what makes the best anchor????

RTF,
The one that holds the best.....

I'll stir the pot..... Danforth.


Seriously though, high tensile steel is tough to beat for material.... galvanized of course.

Conall

I thought iron (black or otherwise) tanks were a thing of the past?? Surprised to hear about a new build with black iron tanks.

No way to tell what alloy it is unless you find out from the tank builder what they bought from the steel mill. Pretty generic term, black iron. If they posted the alloy like many aluminum tank builders do, that would help settle the debate.

What Ski said. Otherwise, just a guess in my experience.

Black iron or steel tanks with modern epoxy coatings are excellent fuel tanks.

Insequent said:

Black iron or steel tanks with modern epoxy coatings are excellent fuel tanks.

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Yes, but proper installation is the key. We're in the middle of replacing our coated steel tanks. The only reason they failed was because of a poor installation.

Most of the steel tank issues are on boats with leaky teaky decks. Water drops on the steel, especially under side decks where water sits on top or runs down the back side where it's not very noticeable, and they start rusting.

A well painted steel tank in a dry environment will last a long, long time. Like the oil tank in your grandmother's basement.

If you go to the local welding shop and look at the "mild steel" lying around you will often see the black shine on the surface from the iron oxide that forms durning production. That's the stuff commonly referred to as "black iron". A very generic term for a number of alloys. They are all steel.