This is only a guess ... cheap mans cleaning solution explained. THIS IS ONLY A GUESS ... I see a chemical reaction with the baking soda being a strong base (not acidic). People use it to clean the acid corrosion on car batteries. The salt acts as a conductor for an electrical current (electrolysis). The aluminum foil I would think acts as an electrode. You stir it to keep the process evenly distributed.
I think you may want to keep the salt and baking soda from being to strong as you may be damaging the metal you are trying to clean. It will also corrode again in the long run.

I welcome corrections to my best guesses!