Here's a good sounding method that I saved from previous postings a couple-a weeks ago. I've since tried it, it works. It's cheap and it's easy.
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RUST REMOVAL BY ELECTOLYTIC ACTION:Solution - 1 tablespoon per gallon of washing soda to water
Power supply - 12 volt battery charger
Anodes - old lawnmower blades work well, basicly any free metal with a large surphace area will work. You have to remove the crap from anodew periodicly, or the current flow drops off. Submerse rusty item in solution, with + lead attached.
Submerse anode in solution, with - lead attached, making sure to NOT short out anode to rusty item.
Turn on charger. If you have proper polarity and good contact with the part & anode, small bubbles will rise from the rusty part.
Scum may form on top of solution, this is normal.
As current drops off, check anodes for accumulated scum, and remove scum.
When part appears to have a coating of black, remove from tank and wash black coating off. If all rust isn't gone, repeat process.
DO IT OUTSIDE, THIS PROCESS IS LAKE CHARGING A BATERY, IT OUTGASSES HYDROGEN & OXYGEN. DO NOT DO IT IN A CLOSED ENVIRONMENT!!! NO SMOKING OR OPEN FLAMES NEARBY !!! Do you have the polarity reversed? According to the link, the positive cable should connect to the electrode, and the negative to the work-piece. Franz Posted 10-25-2001 at 22:44:28 [Reply] [No Email] I might have reversed the polarity, don't know how long I was awake when I wrote it. The best way to check the polarity is to look for bubbles. You should have tiny bubbles rising from the work piece when the polarity is right. That's the thing I always check for when I put something in the tank. I did the front wheel on my farmall A, put it in the bath for about 3 hours, turned it (bath wasn't big enough to fit all of it at once) and let it go another 3 hours. Most of the rust was gone after about 90 minutes, and it was like new, but filthy, cast iron after 3 hours. It didn't harm the bearing races, which I left in as an experiment. I was changing bearings, so I figured I could sacrifice the old races, but they weren't even touched. The length of time it takes can run from hours to a day or more. The biggest governing factor is anode surphace area. If you use an anode that is equivalent to or larger than the surphace of the item you are derusting, it will have maximum performance. With large objects, multiple anodes are best, seems like 1 anode on all 4 sides of the tank is most efficient.
Keep an eye on the ammeter, as the anodes crap up, amperage drops, and so does efficiency. By simply scraping the crap off the amperage goes back up. With a 12 volt charger you don't have any worry about electrocution, but it's a good idea to shut the electric off first, just in case.
Also, the object being derusted should be hung in the solution, that way the crap on the bottom of the tank can't short the tank out.
Get an old lawnmower blade, and the worst rusty C clamp you have, and give it a try. Use a jumper wire to make a second connection on the screw of the clamp, electricity won't flow thru rust well, and give it a try. In a few hours, the clamp should come out looking new. Things like clamps, with multiple parts often need to be jumpered for best performence. When I first heard of the process, I tried a C clamp, and have been hooked ever since.
The best part of this process is that it works pretty much by itself, so you can do other things while you are waiting for the part to clean up. Just like rust, this process works while you sleep. LEWIS Posted 10-21-2001 at 18:16:32 [Reply] [Send Email] I CAN ASSURE YOU THAT THE PROCESS WORKS, BUT THE BLACK COATING THAT IS LEFT AFTERWARDS DOES NOT COME OFF EASILY. IS IT NECESSARY TO REMOVE ALL THE BLACK COATING BEFORE PRIMING? IT LOOKS LIKE IT WOULD MAKE A GOOD BASE FOR THE PRIMER??? Franz Posted 10-21-2001 at 22:29:26 [Reply] [Send Email] I'm not certain what the black crap is that remains on the object being derusted, but it's been my experience it comes off fairly easily with either pressure washing, or washing in dish soap and hot water, immediately after pulling it from the tank. I can tell you though that the dish soap thing works a lot better when the wife ain't home to see it being done in the kitchen sink.
I've used phosphoric acid for years, both as a solution for rusty items, and to convert rust to Iron Phosphate. I have a trailer I built 20 years ago, that I purposely let rust lightly after completing it, then treated it with Phosphoric acid, and painted with enamel after the phosphating process ran its course. Other than where paint has been knocked off by machinery, the original paint is still holding. Arm & Hammer WASHING soda is in the laundry detergent asile in the supermarket. Costs about $3- a box.
Baking soda will work, but it works a lot slower.
Caustic soda (lye) will work, but it's too damn dangerous to handle safely. Try this link. If it doesn't work, go to your favorite search engine and enter "electrolytic rust removal". I found washing soda, which is sodium carbonate (not sodium bicarbonate, which is baking soda, though that will work) at my grocery store. It is made by Arm and Hammer and is in with the laundry detergents. It isn't used as commonly as in the past, so it might not be stocked everywhere. The link lists some substitutes that can be used. Good luck with your de-rusting. I have found it to be a very useful process, but you have to clean off the crud layer that is left over. I use soap and water for that, and dry the parts thoroughly and quickly before they rust again. Electrolytic rust removal
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