Since my girlfriend introduced me to an antiques store a few weeks ago, I’ve been accumulating all sorts of old woodworking treasures. I’ve got a basement full of old hand planes, saws, and hand drills but they all spent a lifetime rotting away in someone else’s damp basement and need a little TLC to get back in working order.
I did some research on rust removal and decided to try a chemical process called electrolysis.
How Does Rust Happen?
We all know that rust is what happens when water and metal come into contact. But there are two other required ingredients: oxygen and time. Rust occurs when iron, water, and oxygen come into contact long enough to cause a chemical reaction called oxidation which results in the chemical compounds we know as rust.
Since we know how rust happens we can prevent it, right? Paint metal surfaces, coat them with wax, yada yada yada. But what’s a guy to do when it’s too late for prevention? There are many rust removal methods, but I chose to try electrolysis based on the minimal labor and the fact that its nondestructive.
What is Electrolysis?
Arthur C. Clarke wrote that “Any sufficiently advanced technology is indistinguishable from magic.” I think the same is true of any scientific process when it’s witnessed without proper knowledge. That’s pretty much how I felt when I came across a couple of videos of electrolysis. Hell, the process even involves a bubbling cauldron and a sacrifice.
So before I decided to hook up a tub of water to a car charger I tried to get a basic understanding of how the process works.
Electrolysis is the process of using direct electric current to drive a non-spontaneous chemical process. In other words, we’ll use electrical energy to start a process can’t start itself and in this case the process is reversing oxidation of iron or iron alloys. You need a couple of things to get the process going:
- A Tank: You need a tank large enough to hold the rusty item. Use plastic or some other material that won’t interfere with chemical the process that’s going to happen inside it. A good bet it a 5 gallon bucket or plastic tub.
- Rig to Suspend the Rusty Item: You’ll need to suspend the rusty item in the tank. I just used some mason’s string and a piece of 2×4 stretched across the top of the tank.
- A Source of Power: You need a source of direct current. I purchased a car battery charger with an ammeter so I could check how much electricity was flowing at any given point.
- Anode: The anode is the “sacrifice” that I was referring to earlier. Scientifically speaking, the anode is an electrode through which electricity flows into an electrical device. It’s where we’ll connect the positive lead from the power source, and is just another piece of iron or steel that will attract the oxygen that disassociates from the rusty piece during the process. Since oxygen, iron, and water will come into contact at the anode, you’ll see rust form rather quickly. That’s why I call the anode a “sacrifice.” A good option is rebar, which is cheap and easily available. Don’t use stainless steel for the anode, as it has chromium which is toxic and releases during the process.
- Electrolyte Solution: You’ll need to fill the tank with an electrolyte solution through which current can pass from the anode to the rusty item. You make this solution by combining 1 gallon of water with 1 tablespoon of washing soda or baking soda. Fill the thank high enough to cover the rusty item but not so high that it will overflow when you dunk the item in.
- The Rusty Item (the Cathode): The item you want to remove the rust from will act as the cathode, or the point through which electricity leaves the electrical circuit. You’ll suspend the item in the electrical solution then connect it to the negative lead of your power source.
Using Electrolysis to Remove Rust
First exercise safety. I’m in no way a professional and I’m not responsible for keeping you safe, so if you doubt your ability to do this task safely don’t do it. Wear safety glasses, wear long rubber gloves, don’t stand over the tank and inhale the fumes, and don’t touch anything once the power is on.
This is the guide that I used with the steps summarized below.
- Make sure the power is OFF.
- Fill the tub with electrolyte solution.
- Place the anode. Make sure that enough is sticking out so that the positive lead can connect without it coming into contact with electrolyte solution.
- Suspend the cathode (the rusty item). Make sure that it’s not touching the sides or bottom of the tub, and make sure you can move or rotate it so that all surfaces can enjoy rust removal.
- Power still turned off?
- Connect the positive lead to the anode.
- Connect the negative lead to the cathode.
- Make sure you’re not in contact with any part of the apparatus, and turn on the power.
- Let the process work for an hour or more, then turn off the power and check the surface facing the anode. If it worked the rust will disappear and the surface might become covered with a black residue that you can wipe off after you’re finished. If necessary give the item more time, or rotate it to remove rust from another surface.