Cast Iron Sugar Kettle Maintenance

POR 15 is what you want. Knock off the flaking rust and simply paint. This product keeps moisture from getting to the metal, thus preventing any further rust.

I painted my cast iron sugar kettle over 10 years ago, and it still looks good.

Your other option would be more expensive ($300+) - bring it somewhere to get sandblasted, primed with epoxy primer, and topcoated.

Thanks for the responses. I noticed today that it has a complete of cracks on the bottom. Any advice how to cover those?

Are you trying to get it to hold water? I filled the bottom of mine with bricks, then added about a foot of soil, then put some plants in it.

Chassis Saver and POR15 are basically the same product, moisture cured urethanes.
Neither is UV resistant so they will fade to a dark gray color and chalk a little.
The fading and chalking doesn't effect their rust resistance.
If you don't want the faded gray, you'll need to go over them with a topcoat.
Personally, I like the faded gray more than a glossy black finish.