Electrolytic rust removal
This morning, before going out to the shop, I checked out the article on Electrolytic rust removal at the Electronic Neanderthal site.
So naturally, the first thing I did was get out the washing soda and those rusty tools I got yesterday, and gave it a try.
First, I got a three gallon plastic bucket, added a bit more than the recommended three table spoons of washing soda (oops!), and added water.
Then I took out the machinists scraper that I'd bought. It wasn't scaly or anything, but it did have a nice even coat of fresh rust, plus some thicker, older patches.
I washed it thoroughly with dishwashing soap to get any grease or oil off, then just to make sure, I wiped it odd with acetone.
Then, using iron wire, I hung it from a piece of wood, completely submerged in the washing soda. I also hung an iron electrode in the same manner about an inch from it.
For the iron electrode, I used an angle bracket from a bed I'd taken apart last weekend. It had a film of rust on it, so I figured that it wasn't galvanized, unlike most pieces of scrap iron laying around my shop.
Then I placed the bucket, electrolyte, and iron out in the yard. I took a four amp auto battery charger up to the iron wires, positive to the iron electrode, negative to the scraper. Upon plugging it in, I got two amps of current, and bubbles from the scraper. Cool!
After a while, I noticed that the current had dropped to about 1.5 amps, so I shook the wooden stick to clear any bubbles off the electrodes. The current went up, but I got a bunch of nasty green stuff in the water by the positive electrode.
Hmmm... Maybe it was galvanized?
The article on the Electronic Neanderthal says, "There is nothing especially nasty about it-it's mildly basic-so disposal is not a concern, except you may not want all the crud in your drains." I wonder what zinc from the galvanized electrode does to this relative non-offensiveness?
By this time, the whole solution was starting to look a bit brown, it was hard to see down into it.
After about an hour and a half, I turned the scraper around to expose the other side to the positive electrode. After another hour and a half, I decided to take it out and have a good look. At this stage, the electrolyte was utterly disgusting, and a nasty ring of crud was forming on the bucket walls at the surface.
Following the instructions, I scrubbed the scraper off under running water. It looked great! A few pits, but all the rust was completely gone!
Being warned that the clean object would be very rust prone, I cleaned it a bit more with 0000 steel wool and WD-40, then rubbed it down with motor oil. At this point, I could see the grinding marks left from when this scraper was made from a file, as well as read the brand name of the file (Nickelson). This a a *very* gentle way to remove rust indeed! And it worked the first try, nothing finicky about it.
After doing the scraper, I did one of the augers. Similar method, results almost the same, except that I think I got lazy and didn't clean it well enough at first, as one spot was not touched. A little more cleaning and more time in the bath, and I had a really nice bit. Once again, I could even see machining marks, as well as a maker's mark that I hadn't even suspected ("VT").
By this time the bath was so disgusting that I decided not to keep it, I'll just mix more up next time. Almost black it was. The bucket was quite easy to clean though, the stuff didn't stain at all.
All in all, quite an easy way to remove rust. It takes a while, but most of the time is unattended, and the set up and clean-up are far easier than removing the rust with other methods (well, at least reasonably gentle methods) would be.