Sometimes we're faced with powder coating projects/jobs that involve heavily rusted items. This was the case with my most recent project. I wanted to powder coat a pair of steel rear calipers for a Mazda that have been oxidizing for almost 10 years. The rust was so heavy that you could knock it off with a screwdriver in some parts. I tried blasting them with aluminum oxide but after about 10 minutes I seen that the progress was not worth my effort. While glancing through the home shop/hobby magazines during a chance visit to a local Chapters that day provided a solution. Removing rust by simple low volt electrolysis. Here I will detail my setup and provide a couple links that show more setups.
My setup consisted of:
1. 5 gallon bucket
2. 2 sq.ft of ceramic tile lattice
3. Arm & Hammer Washing Soda
4. 6 Amp battery charger
5. 2 ft. of steel rod
6. 3 ft. of 12 gauge insulated copper wire
Steps in creating my setup:
I took the ceramic tile lattice (this stuff you can buy at the local hardware store and it is used to strengthen the cement base when laying floor tiles) and cut out a circular disc just smaller than the bottom of my bucket. Then I cut out a rectangular piece of lattice with a width smaller than the height of my bucket, about 2 inches shy of the bucket rim. The length was about 10% less than the circumference of the bucket. Than I proceeded to bend the rectangular piece of lattice around the circular disc I cut out earlier. What you want is a cylinder made out of the lattice that you can put in your bucket. I did this because the electrolysis works more of less on line of sight. This gives a good electrode as the surface area is large.
I then took a 3 ft. piece of wire and attached it to the lattice securely. I then put the lattice in my bucket.
I then proceeded to add about a tablespoon of Arm & Hammer Washing Soda to each gallon of water. If you put in a bit more it won’t hurt a thing. I then filled in with warm water and gave it a good stir to dissolve the Washing Soda.
I then took my caliper (aka. widget) and connected it with the other 3 ft. piece of wire. Sometimes it is very hard to get a good connection because the part is rusty so I had to grind some of the rust off to get a good connection.
I then immersed my item into the solution making sure that it did not touch the lattice anywhere. I stopped the part from dropping to the bottom by making three wraps of my wire around my steel rod. Once I was satisfied that my part was not touching the lattice anywhere I placed the steel rod across the bucket.
I then proceeded to connect the POSITIVE lead from the battery charger to the electrode, my lattice. The negative lead was connected to my part. The polarity is VERY IMPORTANT. If it is hooked up backwards (negative to electrode, positive to item) you will actually build more rust on it, it will oxidize even further and at a very increased rate!!! You will destroy you item!!!
I then proceeded to turn on the battery charger. If you have an Amp meter on your battery charger you can see how much current the electrolytic process is using. You can always test it with a multi meter. Almost all modern battery chargers will at least have a voltage indicator. If the voltage is extremely low you probably have a short circuit, you part is touching your electrode. Correct at once. My volt indicator was showing an average of 10 volts when I was doing my calipers. It might rise slightly as rust is removed and more metal is exposed to current flow. This process will generate oxygen and hydrogen, not a lot, but I would advise a well ventilated area. No smoking or open flames!!!
Overall I find this process very ingenious and satisfying. My calipers, of which there is a picture available in the album were immersed for about 6 hours. I was in a hurry and this is all the time I allotted my self so all the rust did not come off. If I had left the process overnight I believe that all of the rust would have been gone.
Maybe some of the plating/anodizing guys can recommend a better solution.
I include some links for more information and varying setups:
http://www.oldengine.org/members/billd/electrol.htm
http://www.stovebolt.com/techtips/ru..._derusting.htm
etyrrany