I can't remember which show on Velocity Channel it was on. But in a video clip they set up a pump and hose and a plastic sheet to catch the liquid.
They put a gallon or two of EVAPORUST into the catch sheet and the pumped it up to a top of a partly rusty door. The stuff run down the door and was pumped up all over again.
Left to run over night the next day the rust was gone but paint untouched.
I just bought my first gallon last week and looking forward to setting up a dip tank to put rusty parts in.
Once you run this you will have clean bare metal and will need to treat it so it will not rust again. The company (evaporust) makes treatment for bare metal I think.
I know I had seen some on one of the shows.