Cast Iron Radiator Heat Exchangers

[Norwegian Wood]

I'm halfway through building my 1000 gallon water storage tank.
With the cost of copper being what it is, I was wondering if I could use two or three reconditioned thin wall cast iron radiators as heat exchangers for the EKO loop.
I know copper has a way higher thermal conductivity than cast iron, about 6-7 times, but I will have a much larger surface area than coil tubes, and my intuition tells me this should work just fine, at a much lower cost.
I've seen a couple posts where this is mentioned, but apparently nobody has tried it.
Or has someone?
Any thoughts from the forum?
Thanks.

 

[bmblank]

I'd be concerned with air lock. Other than that they're probably fine. Maybe if they're mounted upside down airlock won't be an issue.

 

[tom in maine]

They will corrode. There is also a risk of damaging your liner given the weight.
Copper is a cheap date for a heat exchanger. Another option is to use a plate hx. You would need a second pump, but
it might be a bit less expensive.

 

[Norwegian Wood]

Would powder coating stop them from corroding? The insides are built specifically to carry pressurized high temp water, and they last 100 years +.
The outside I get, but I figured powder coating would buy me thirty years or so.
I can distribute the weight using picnic cooler tops. They last forever.