Ingot molds...

[Burnt Fingers]

I lucked into some cast iron ingot molds. However they are heavily rusted.

Should I just use a needle scaler to remove the rust or go the Evap-O-Rust route?

[Valley-Shooter]

I would use the cheapest method available. Needle scaler or wire brush.
They don't have to be pretty. A little rust won't hurt.

[DGV]

I used a cabinet sandblaster to clean a set of rusty lyman ingot molds. They looked brand new when done

[deltaenterprizes]

What DVG said!
Vinegar will work also or most soft drives with phosphoric acid in the ingredients.

[lightman]

If you have access to a blast cabinet thats worked well for me in the past. A cheap wire brush chucked up in a drill will work. Evaporust also works great.

[Conditor22]

Don't kill yourself cleaning them unless you're anal about that (I'm not saying that is a bad thing)

Just knock off the loose rust and you'll be good to go.

[MrWolf]

I left my corn muffin moulds out so they developed rust. Lead releases easier that way. Good luck

[Burnt Fingers]

These have some really scaly rust. A wire brush in a drill won't get into the corners very well. I don't have a blast cabinet.

[Mytmousemalibu]

Set up an electrolysis tub and attack it with that. May need to gove ot an occasional scrub with a brush to help it out but that will do the trick.