There isn't much market for them as radiators, as scrap, it will vary depending on where you are at. Cast iron is the least valuable iron and the price will vary day to day. $20 to $100 a ton.
The rule of thumb $100 per section
Of course NOT A Problem as electrolytic action most of the times happen between piping that contains galvanized coating (Zinc) Cast Iron radiators for example have BRASS valves which can contain as much as 85% copper If one looked at the clean outs of cast iron piping the CO's are brass with never any adverse actions
Are you considering this in a residence? A friend of mine converted a residential steam system with cast iron radiators to hot water for child safety reasons. It all worked, but he had to deal with some water leaks at joints in the radiators. That was a nuisance. The amount of heat delivered to the house will be different with water, but I can't remember if the radiators are oversized or undersized after conversion. In his case it heated fine. Call a professional. EPM
Malleable cannot be broken like a cast fitting can be and normally malleable fittings / pipe do not have a seam +++ Its full name is Malleable CAST Iron - it is cast as "ordinary" cast-iron but is a lot less brittle. It is an important material combining some of the properties of cast-iron with those of mild-steel.
No
I don't think they make cast iron anymore. About the only way to replace cast iron is to go to auctions or yard selling to find the. You can try to repair the skillet if it means that much to you.
SO they don't melt on the stove. Also they are durable, good conductors of heat. Copper pans are much more expensive, and so are cast iron ones.
1.9 billion
About 500 TONS (empty)
I just bought one for $1,290
250 pounds
Cast iron is brittle compared to other steels, so excessive force could break it, as it does not yield well. In addition, it will rust (oxidize), unlike stainless steel