I do not know of anything you can spray on and really remove it all, even with most chemicals it still takes a bit of elbow grease and usually needs to submerge and soak the metal completely.
You could try muriatic acid, Ive never used it personally but I know some people do use it on rusted body panels. Read that its some pretty nasty stuff too, so protection gear will be a must. Look into it with a google search.
Other then that, I can suggest a good Respirator with new filters (NOT OPTIONAL, NEEDED) and angle grinder with wire wheel and get to work. And o yeah eye protection goggles not glasses.
Btw, Is the frame off the body?