We need a paint that can be sprayed, to coat the interior of cast iron columns. The aperture into the columns is only 80mm diameter, at the bottom of 8m high columns. We will only be able to remove the loose corrosion/deposits from the cast iron, it will not be a perfect surface. Appearance doesn't matter this is all to inhibit corrosion.
Assuming the internal surfaces of the cast iron columns are clean, dry, sound and prepared as detailed in the Technical Data Sheet we can recommend Rust-Oleum 9169 Epoxy Rust Primer.
This can be applied by conventional and airless spray.