I have used it with great results on rusted items. Works by "line of sight" from what I am told. Meaning that the area to be treated must be between the + and - electrodes. I have never tried to do the inside of an item, ie: gas tank ,for this reason.
It puts off a lot of hydrogen gas so do it in a ventilated area. My setup is a 55 gal plastic drum and a DC welder. Heavily rusted parts are in for a day, then cleaned as much as possible and returned to the tank to finish. Parts are washed afterward and primed. Takes them down to bare metal and will remove paint.
Matt
i have just got done setting up the tank... its outside of my shop... i know it will work a little slower from what i understand... when i hooked it up to the batter charger 12amps it started to bubble so i guess ill just sit and wait!