at the junkyard

easy: build a suitably sized frame of wood. line the frame with a large sheet of heavy duty plastic ( the thin, flexable kind), and place the item in this "tank". cover with distilled white vinegar, not the brown kind. will take several days. every now & then, remove some of the gunk with a stiff bristeled veggie brush. this is messy, but works on restoring old rusty metal files to brand new condition.

once satisfied, discard the vinegar gunk and refil the tank with common baking soda and water. this is needed to neutralize the acetic acid ( vinegar). if the neutralizer bath is not done, it will re-rust in about a day. once it's properly neutraliized dry it as quick as you can, and apply oil , wd40, or such.

this will be a pita to do, but will work. try an old rusty file or such to see what to expect. do not do this near the house. it could be the end of yer marriage !!!

there's scads of videos on the net on specifics of doing this procedure. it's possible to do this with electricity, but is more complicated and expensive to do a piece this size. i've done both ways quite successfully. good luck