Welding Black Iron into tanks

[HarlenW]

I am not a welder but have a welding question about Black Iron. I am looking at a boat built in 1988 in Taiwan that states it has Black Iron diesel fuel tanks sealed in fiberglass mat and epoxy. This information is from the original boat brochure from the maker Hans Christian, a reputable boat builder of that era. The problem is that a member of a boating forum I belong to said that it is very difficult to weld Black Iron into a tank. Also, a surveyor I contacted said he doubted it was Black Iron but more likely Mild Steel.

Can Black Iron be welded into a large diesel storage tank of 200 gallons?

Is Black Iron less likely to rust than mild steel?

Thanks.

Harlen

[Nunya]

Black Iron is a catch all name for mild steel. The black iron title is still used on some structural blue prints, although it is becoming rare. Here in the U.S.A. construction workers usually call iron by the color of the paint applied to primed steel, such as, red iron (red oxide), gray iron and black iron. Black iron plate usually has a mill scale and black iron pipe is usually covered in some sort of paint and/or varnish.
If it was built in 1988 I seriously doubt that it is "iron". It's probably similar to, or is, A-36 mild steel.

[Nunya]

I hit submit too fast.
Lots of ships and buildings were built from iron until somewhere around (?) 1920's. That is a huge guess.

Wrought iron has a very low carbon content as compared to mild steel which can have up to .30%. Iron also has a mixture of slag and silica (glass) in the contents. This slag and silica give it a fibrous grain and help prevent rusting. It will rust, but not as rapidly as mild steel which does not contain the slag and silica.

If the tanks are fiberglass wrapped and everything was built in the mid 80's, I still say it is mild steel.