This is a process called Chelation. Its 1 part feed grade molasses to 9 parts water. Softer ferrous metals i have found it will eat. Stamped steel sheetmetal it wont eat. I lost a whole batch of sems fender screws and nuts because i wasnt paying attention. Luckily i found a wholesale supplier to replace these with new, however i still need to find the 5/16 wide washered nuts. It also eats off the crappy factory black dipped paint too
You need a plastic tub with a lid or large plastic trash can with lid depending on what you want to dip. You need enough solution to completely submerge the part. I found a rectangular 35 gallon trash can i plan on buying and using for wheels and my K frames.
Depending on the rust some parts clean up in a few days some in a little over a week. I had an oem mopar battery tray that took 8 days but was clean pitted steel when done. No brown corrosion spots. I tend to check on everything every few days. My sems body bolts i forgot about for 2 weeks, thats what killed them.
Once the parts are all cleaned of rust, you cannot let the air get to them or flash rust will occur. The trisodium phosphate powder mixed in solution with water in a pump type plant sprayer is what you need to use. 1/4 cup TSP to a gallon of water. Take 1 part at a time lift it from the molasses mixture and before the molasses water mixture dries on it you have to hose it off right away thoroughly with the water/tsp mix, then let air dry. I plan on making a drying rack with hooks to hang parts to air dry. The TSP in solution with the water allows rinsing of the molasses mixture and prevents flash rust. You can buy the tsp at lowes or home depot in the paint supplies section. A small box is about $3
Prep work for paint after it dries, well there is no prep work. As long as the part did not go into the solution greasy , and has residue still on it, just prime and paint. To be sure just wipe the parts down with a bit of laquer thinner and a clean cloth, or paper towel.
The molasses solution is non toxic, and can prob be used as plant or grass fertilizer when not needed anymore as it has a high iron content when it disolves rust.
(I'd recommend trying it on a spot first)
The bad part is the stink. This stuff stinks BAD!!!! Wear heavy duty rubber or chemical resistant gloves when working with it, as it absorbs into your skin then no matter how much you wash, your hands smell like it for days.
Anders you mentioned finding molasses, check a local agricultural feed store. A gallon cost me $10. For $20 more and a large trash can i will be dipping steel wheels and K frames LOL.