Hey 51 --- if all you need to do at this time is stabilize it and prevent further rusting, try a "Rust Converter". There are a number of brands on the market that are available at most auto parts stores. I've been using one by Quest Chemical called "Restore" that works like a champ. They are acid based and interact with the oxides (rust) and convert them to a stable organic compound that simply can't rust. The product above also contains a polymer sealer and is the only one I know of that does not require top coating. All the others are rated as a primer only.
Course, like Mr Fords Model T's, they are available in any color you want, as long as it is black.