Metal spray to repair cast parts.

The material for a foot would cost you more than a complete floor.

My son does spray welding on engine blocks . Its $300 to $400 for a couple of oz's just for the iron material. It does not go far.

Spray welding is the most expensive welding for material use. These types of repairs are for restorers with very deep pockets that cannot find very expensive parts. Also you cannot weld onto rust with any type of welding. You will just blow a rusted floor away.

You would be better off using JB weld after blasting it to bare metal