Rust and Corrosion remediation

[jOe]

After numerous basket cases and barn finds with countless coffee cans filled with nuts, bolts, washers and other hardware that have developed decades worth of rust I figured I'd share a couple of methods that I've seen and used. There's a number of products on the market today that work to a point, but short of bring everything to a professional metal finisher and getting them pickled and coated (risking the loss of some of the little gems) there"s not too many options.
The first one I learned about one day from Ben Hardy. I was in his shop one day and he was soaking some hardware in a 50-50 solution of muriatic acid (HCL) and water. He periodically pulled a piece out to check on the progress. When they were clean he transferred the lot into hot water, then blew them off with compressed air and dumped them into a can of used motor oil.
It works pretty well. I've used this method several times, but don't necessarily endorse it. It's messy and you really have to keep an eye on things as to not overdo it. It won't remove paint.
A couple of exits down the 110, Bob Ross used a homemade lapidary and tumbled everything clean. There didn't really seem to be much of a downside to this method except for an occasional pebble lodged in a nut. This method also was good for deburring and if overdone will round off crisp edges.
But here again, while the hardware was clean, there was no finish on the completed pieces and they are prone to re-rusting.
Now, prior to 1939 when Dulite (parkerizing) was developed I believe H-D painted much of the hardware.
I'm staying away from bead blasting on everything these days. I know it works, but I'm never sure that all the beads are completely gone.
Has anyone tried things like ultrasonic or electrolysis to get rid of rust?

[hennesse]

Check out this article on using Oxalic Acid to remove rust.

Sounds like magic, huh? Well, I did two very limited tests using 3 tablespoons/gallon, and some small nuts and bolts in a spaghetti sauce jar. After 4-6 hours, the rust was coming off, but it needed more time, so I left them soaking overnight. The next morning, the rust was gone, but instead, the parts were covered in a gray residue which needed wire brushing to remove. There was a lot of gray matter which had fallen out of solution, and was lurking on the bottom of the jar, but didn't stick to the glass.

I just haven't had time to do any more testing, but I have a couple ideas for next time. First, a larger volume of solution so the ferric oxalate (or whatever that gray stuff) is is not so concentrated. Second, suspend the parts off the bottom of the container, so they're not down in he muck. Maybe run the solution through a coffee filter after 4 hours to get rid of the byproduct. Third, maybe lower the strength of the solution.

Has anyone else tried oxalic acid? What were your results?