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 Post subject: Electrolysis Rust Removal
PostPosted: Fri Feb 21, 2014 12:05 pm 
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Joined: Sun Mar 15, 2009 9:10 am
Posts: 96
Location: Golden Valley
One of my other projects is taking the subframes and running gear from a miata and putting a tube frame chassis on it. It's a kit car called an MEV Exocet. In removing the subframes and other pieces I came across a lot of rusty bits. I hate spending hours wire wheeling, sanding, applying POR15 rust converter, and a miriad of other techniques that require copious amounts of elbow grease to get a result that is still below a decent result.

Enter Electrolysis!

This still requires a bit of scrubbing, but it's not nearly as involved. The big reason for using this technique is that I get to build another super sweeet project!

(Non-technical explaination) Electrolysis works by removing the rust, and other things like grease and paint, from the part by curring a current through a bath of water and detergent. The rust either falls to the bottom of the tank or adheres to the anode (positive connection). Attach the Negative to the part and the Positive to some other metal that will be in the bucket. The process is mostly line-of-sight so an array surrounding the part works best. You can also put an anode inside the part and clean the interior. Always be careful to not let the cathode (your part) and anode (whatever is attached to the positive) touch.

Essentially all you need is a bucket, a battery charger, some steel rods, and washing soda (also known as soda ash or sodium carbonate. NOT sodium BIcarbonate, thats baking soda, it'll work just not as well) at a ratio of about a teaspoon per quart in a non-conductive container.

This setup is good for small parts, but my parts are much larger, so I need a bigger rig. I have several transformers sitting around and doing some seat-of-my-pants calculations (i.e. guesses) I determined that I can use a couple of them in series to get my desired voltage and current. One of the things to note is that if you use too high a voltage you could cause hydrogen embrittlement in your parts. Higher voltage means you can get the parts finished sooner, but I'd rather not risk embrittling things I'm going to be riding on at high speeds. More current will speed the process too but is more easily adjusted. To adjust current you can either move the part farther away from the anode to reduce the current flow, or you can use less sodium carbonate.

The transformers I plan on using are from some old thermal label printers and are 120v:27v stepdown transformers, or a 1:4.44 ratio, and 200VA rating. Putting them in series will yield approximately 6v which should allow me to get about 30 amps of current safely. I'm going to use a switch to allow me to use the 27v for less critical parts.

I'm going to knock together the transformers and stuff this weekend and I'll try and build the tank, but that might take me a couple more days. The tank will be made from some old fence posts and pickets I have lying around and should be about 5' x 4' x 2' high.

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 Post subject: Re: Electrolysis Rust Removal
PostPosted: Sat Feb 22, 2014 5:43 pm 
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Joined: Sun Mar 15, 2009 9:10 am
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Location: Golden Valley
Got the box knocked together. I simplified the design by not having a switch to go from the higher voltage to the lower, instead I'm just using an outlet with the two plugs going to the different rectifiers. The two transformers work exactly as I expected and the voltage drop across the rectifier brings the second output to exactly 5V ±0.2, the upper is 24.5V ±0.2. These transformers are good for 200VA, so 40A at the lower voltage and 8A at the higher.

I made the plug from an old battery charger, ironically, and spliced the plug and clips together, which makes it about 12' long. The entire box is a good 20lbs.

The next step is to find something rusty and put it in a bucket of solution.

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Instructables is my crack.

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 Post subject: Re: Electrolysis Rust Removal
PostPosted: Sat Feb 22, 2014 8:01 pm 
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Posts: 8
Watch the cooling on the 5V rectifier & transformer when you run it at high current.

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 Post subject: Re: Electrolysis Rust Removal
PostPosted: Mon Feb 24, 2014 10:51 am 
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Joined: Sun Mar 15, 2009 9:10 am
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Location: Golden Valley
I was able to do some testing yesterday, the results are promising. I started with 5V and measured the amps at about 4.5 - 6.5A. It took about 6-7 hours and looks like it could use another 1-2 hours. I then tried a similar part at 24V and immediately blew the 1.5A fuse I had on the AC plug in. I decided to bypass the fuse since I was plugged into a 15A GFCI outlet I figured I'd be ok and I'd monitor for heat. The reaction was very vigorous and the solution immediately started bubbling. After about an 40 minutes the 24V test was almost as good as the 5V test subject.

I didn't test the amps on the 24V test, when I tried to connect the leads there was a good size spark and a bit of my probe was slagged. I'll wait until I get my volt/ammeter in the mail and provide results then. I also think it would be a good time to implement the dimmer switch to help with voltage/current regulation, if I can locate one of the old-school resistor dimmers.

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Too many irons, not enough fire.


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