I've used vinegar, the cleaning concentration, which is higher than the food-grade. I used Heinz, 6% for these projects below. There are some very-high concentrations, I've seen as-high as 30% but I've never used that. If you do choose to use that, I suggest checking hourly, until you get the results you want.
I was-given a plastic toolbox of mixed sockets and wrenches (pic #1) which went-into a cleaning vinegar bath for a couple of days, and they tools cleaned-up well (pic #2). When I removed them and rinsed/dried them, I hit them with a wire brush, and then shot them with PB Blaster, wiped them-down, and sorted them, and stored them. They're just back-ups. They came-out much-better, and they were east to identify, the sockets were a mixed-lot of MAC, S-K and proto, and others.
Another cleaning vinegar project I did was something to hang in the garage, a pedal car front end piece, from a Murray 'sad-face'. The entire thing was consumed by rust, I cut-off the only part which looked like it was worth saving (pic #3), and threw it into the cleaning vinegar (pic #4). Again, a thorough rinse and dry, then I shot it with Martin Senour paint (pic #5). I want the pits and holes, but not the rust.
I used the same vinegar for both the tools and the pedal car face.