I tried this one I bought a nice new Ingersoll rand needle scaler to take the rust off the frame of my old truck and of course just like my harbor freight air tools it didn't work. Well I fix that three years later anyways by filling it with many ounces of ATF / acetone and letting it sit 3 days. In the meantime I found something better . So much less air used dirt cheap to buy and you probably already have one, the handy dandy pneumatic air chisel.
This is my other go to toy for when I have ultra Rusty nasty frame bolts and such and I don't want to or can't get in there with the torch without burning things up. Just put on a blunt tip or cut off an old one and round it and let her hammer away with your best limp wristed style and penetrating oil. Works like a charm just let it bounce. For cleaning steel heavy flake rust comes flying off in pretty short order and it's a whole lot easier to use than a needle scaler. For rust I just use a fairly blunt air chisel tip and like I say hold it with your best limp wristed style let the thing just rattle on the rust and it cleans those frames right down like you wouldn't believe . At least in my experience if you cut through it's usually because it's so rusty it go through anyways. Anyways that's my accidental new idea and it works fine for me so give it a try sometime. It sure beats bang in with a hammer and scraping with Needle scaler.