This article describes how to use Electrolysis rust repair for automotive applications. Nuts, bolts, brackets, body panels and pretty much anything that is carbon steel or iron can be repaired in this way! Electrolysis is generally regarded as the safest way to restore rusted metal, and is frequently used for antique repair and by museums.

We demonstrate the process on a set of rusty original drum brake rotors for a 1972 Oldsmobile Cutlass Supreme (Check out the project HERE!!).

How It Works

Electrolysis sounds complicated, but really it’s not too bad. A high school level of chemistry is enough to understand the premise. A power source is used to impose a positive and negative charge in an electrolyte solution. Thinking back to high school chemistry, many atoms have a positive or negative charge or potential, based on their electron cloud configuration. Oxygen has a negative charge, and hydrogen as a positive charge. This is why electrolysis can be used to generate oxygen and hydrogen gas. Remember that in chemistry opposites attract! The oxygen will move towards the positively charged electrode (AKA the Anode), and hydrogen will move towards the negatively charged electrode (AKA the Cathode), thus splitting water in half (Water is H2O)!

Now back on topic. “Rust” is iron oxide, or Fe(Ox)y, or various forms of oxygen (O) bonded with iron (Fe). Reference your periodic table of elements. As discussed above, because Oxygen has a negative potential, it will move towards the positively charged electrode (The Anode). This is critical to remember!

Can’t keep cathode and anode straight, don’t P.A.N.I.C.!  Positive Anode Negative Is Cathode

Application

We will need a few simple things to setup our electrolysis process, all of which should only take about 15 minutes.

1. The Cathode. The part you are de-rusting.
2. The Anode. A graphite, iron, or carbon steel donor piece, or the part you are sacrificing. Graphite rods or blocks work really well as they help keep the electrolyte solution cleaner, although they are not necessary. We used old junk brake rotors as they have a high surface area, contain no stainless, and are free! Old Crankshafts, wrenches or whatever you grab from the junkyard should work just fine.
3. Car Battery Charger. 12 volts DC. Preferably with a Manual option, rather than an automatic charger. A 12 volt car battery will work, although it will likely be slower and eventually drain. Ideally the battery charger should have an ampere (current) reading so you know if the process is working.
4. Big plastic tub. Big enough to completely encompass the part you are de-rusting, and at least part of the part you are sacrificing.
5. Washing soda or baking soda.  Note, washing soda is sodium carbonate, baking soda is sodium bicarbonate. Washing soda is ideal, although backing soda will work as a substitute, just slightly slower because of lower solubility in water.
6. Some wire to connect the charger to the anode and cathode.

Reference the following graphic for the general setup.

Before we setup the process, which is very simple, let’s review a few un-obvious safety concerns.

1. Because this process strips oxygen and hydrogen and releases it to the atmosphere, the potential for an explosive accumulation of gas is real. Work outdoors or with excellent ventilation.
2. Don’t use stainless steel or other exotic alloys as your Anode (sacrificial piece)! A main component of stainless steel is chrome which is toxic. The chrome will be deposited on your Cathode, which isn’t necessarily bad, but the chrome can also be converted to hexavent chromium in solution, which is a potent carcinogen, especially if you are working with an acidic solution.
3. Work with a basic solution (pH of 7 to 14). Washing/baking soda will result in a basic solution. It will be safer and help reduce rusting after electrolysis is complete.
4. Don’t electrocute yourself. You’re putting electricity in a conductive solution. Don’t touch anything with the power on or plugged in. Ideally work with a GFCI outlet.
5. Wear latex/nitrile gloves and safety glasses to protect yourself from dangerous chemicals, alloys and pH.
6. Watch kids and pets.
7. Don’t use salt as your electrolyte. Salt is NaCl, with Cl being chlorine. Similarly to stripping oxygen, electrolysis will strip chlorine and produce chlorine gas, which is highly toxic.
8. DO NOT use this process for springs or other high tension metals. Electrolysis can produce hydrogen and cause hydrogen embrittlement of the Cathode, which reduces the strength of the metal and can cause cracking/fractures. The electrolysis likely won’t occur long enough to cause this to a significant degree, however better safe than sorry.

Let’s begin! Here are a couple general notes regarding setup to help you be more successful.

• More current = Faster progress.
• Power supply voltage—More volts, more current.
• Size of workpiece—Larger workpiece, more current.
• Size of “waste” electrode—Larger waste electrode, more current.
• Workpiece/waste electrode spacing—Shorter distance, more current. Longer spacing, less.
• Strength of solution—Stronger solution, more current.
• Whatever you connect to your Anode in the electrolyte solution will end up on your Cathode. Example, If you use copper wiring to connect your Anode, you will end up with copper electroplating on the part you are restoring. Not necessarily bad, but be aware. Steel wire or coat hangers are available if you don’t want this.
• For best results, avoid Channeling. If you only have one Anode, the de-rusting will occur primarily in the area directly between the cathode and anode. For quicker and more uniform results, use multiple Anodes connected with wire which surround the restoration part.
• You can restore multiple parts at once! Simply connect each with wire and connect the wire to the Cathode (power source).
• Anything that makes water conductive can be used as an electrolyte source! We recommend washing soda as its effective, cheap and fairly safe. In theory, you could use vinegar, sugar or many other soluble solutions, however with varying forms of success and danger. Do your research if you’d like to use something different.
• Electrolysis will not damage the existing un-oxidized portion of the cathode in any way. It WILL however likely cause paint or coatings to lose adhesion.
• You can re-use your electrolysis solution as many times as you’d like. Although if you use old rusty parts as the donor steel, the solution will likely get really scummy with iron oxide. It will still work as long as your electrical connections are solid.

Procedure

1. Place Anode(s) and Cathode in the plastic bucket you’ll be using.
2. Fill bucket with enough water to completely submerge the Cathode (part to be restored).
3. Add one cup of washing soda per gallon of water. An estimate is fine, no need for an exact measurement.
4. Stir.
5. Connect Black (Negative) battery charger terminal to the Cathode. The terminal can be submerged, as this is the part being restored, however it’s not recomended. Ideally, connect the Cathode with wire, and connect the battery charger terminal to the wire. This will ensure no corrosion to your terminal.
6. Connect Red positive battery charger terminal to your Anode. The battery charger terminal must NOT be submerged, as it will be sacrificed along with your Anode! Use wire of your choosing to connect. If the sacrificial part is highly rusted, wire brush or clean the rust off of the terminal connection point to ensure good current flow.
7. Turn on your charger to 2 amps in manual mode.
8. Wait!

The process is generally fairly slow. Depending on the severity of rust, de-rusting may only require a few hours. Severe rust will require operation over night. If the process is working, you should see bubbles forming on the cathode and anode. DO NOT get your connections reversed, as this will CAUSE rust on the part you are trying to restore!

Once the electrolysis is complete and you are satisfied with your results, make sure you inert your components quickly! The new bare iron molecules will oxidize almost immediately. Use oil or phosphoric acid to inert the iron to prevent corrosion, or simply clean and paint immediately.

Here are a few pictures of our 10 minutes setup and results! We did this as a last minute chemistry project on a Sunday afternoon, so don’t judge too harshly!

Congratulations! You just restored an ugly and rusted metal part for nearly FREE! Share what parts you’ve saved from rust below!

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