You could clean them up with chemistry, specifically electrolysis. I use it to clean parts that are still serviceable but rusty. You need a few things:
1) 5 gal. bucket
2) Some scrap steel that will reach the bottom of the bucket and stick out of the top about 2". I use 1" flatbar, but anything steel will work (rebar, etc.). You need 4 or 5 pieces.
3) Some wire. It can be anything, stripped out solid Romex, fence wire, anything that will conduct electricity.
4) A 12V non-automatic battery charger
5) Arm and Hammer Laundry Detergent (about a tablespoon per gallon)
6) A stick long enough to reach across the bucket
Fill up the bucket with water (leave at least 6" or so at the top), add the appropriate amount of Arm and Hammer and mix it up by hand. Just stir it in good, no need to make bubbles. Affix the scrap steel to the sides of the bucket with clamps (spring clamps work great). The process is "line of sight", so if you're doing u-bolts you'd want to space the scrap (the electrodes) evenly around the rim of the bucket. Connect all the scrap together electrically with wire. I drill holes in flatbar and run fence wire through them and braze them, but as long as their all continuous (again electrically) it will work. Take the piece you want to clean, say the u-bolt, and suspend it in the bucket, completely submerged, from the stick by another piece of wire. Now the fun part. Hook up your battery charger as follows - do not reverse the connections or your part will get more rusty - the positive clamp to one (and thus all) of the scrap around the rim and the negative clamp on the wire that your part is suspended from. Turn the charger on. Nearly immediately you will see bubbling and within minutes rust will float to the top. The majority of it will stick to the scrap. If you're dealing with a lot of rust, you may have to remove the electrodes after a few hours and scrape them off (the reason I use flatbar). The water will not shock you. This process is self terminating, i.e. you do not have to catch it when it's done and it will not remove steel from your part, only rust. I let mine run at 6 amps overnight usually. If you've never done it before, you'll be amazed at how well it works.
Here's the only pic I have of one of my runs, I was removing rust from the front side of a crankshaft pulley (which is why all of my electrodes are together). It came out looking new. For bunches of little parts, or multiple parts you can suspend them in a wire basket. Just remember it's line of sight. If you can't draw a line from a section of your part to one of the electrodes, it will not be cleaned as well if at all.
