Cleaning Frame/Corrosion

[natez]

Please take a look at the attached pic.

I have my DS bodywork off for paint, also took the batteries out to clean things up and tidy up some wiring. Is there a recommended procedure for cleaning/treating areas like this, especially were the battery spilled some fluids and corrosion exists? I'm thinking of coating it with automotive undercar coating after cleaning and treating.

Is there something easy I can do such as I would with a steel part that is rusted (brush off rust and coat with ospho and then paint)? I'm not looking for it to look 100% new, just don't want it to continue to get worse and want to clean it up.