Backyard DIY Electrolysis for Rust Removal on Cast Iron and Tools
I'll bet everyone reading this has a secret stash of rusty something-or-other; Granny's Dutch oven, tools left in the rain, a cool garage sale find. If only there was some quick and easy way to return the metal to bright and shiny...
There is. Here's a sweat-free, pain-free method of removing every particle of rust from your rusty junk- using the miracle of electrolysis and some random stuff you probably already have laying around.
Step 1: Equipment for Your Miracle
Here's what you need:
An automotive battery charger, 10 amps or bigger. A smaller trickle charger will work, but it might take weeks instead of hours to remove all the rust. One with a built-in ammeter is best, so you can tell when you have a good connection.
A plastic tub, bucket or container, big enough to suspend the rusty article completely free of the sides and bottom; you want the solution to circulate freely. You can also line a cardboard box or basket with plastic to hold the solution- anything will work if its sturdy enough and can be lined in plastic
Arm & Hammer WASHING Soda (not baking soda). You'll find this in the laundry detergent aisle.
Steel for the anode- rod, sheet, bar, whatever you have handy or can buy cheap. Old metal junction boxes, pieces of rebar, literally whatever you have. The more surface area the better.
A non-conductive rod to suspend the rusty article from. I used a piece of CPVC pipe, but wood is good too.
Some wire, any kind
Step 2: Safety First
Do this outside, please.
You will be generating some hydrogen gas and you don't want any explosions in the garage.
Step 1) Fill the plastic container with a measured amount of water- when filled, you will add 1 Tablespoon of washing soda per gallon of water; stir to dissolve. Tip- make the last gallon you put into the tub HOT water, you can dissolve ALL the washing soda in the hot water and you'll get a fast, thorough dissolve.
Step 2) Place the non-conductive rod across the top of the solution container, and wire your rusty article to is so your article hangs completely submerged, but not touching the sides or bottom.
Step 3) Place your anode steel in the solution (the anode can touch the sides and bottom, and it can stick out of the solution too) but make sure it is AT LEAST 2” from your rusty article. Any closer and you will pull too much current on your battery charger and might damage it.
You can use more than one anode, such as multiple pieces of rebar on different sides of the rusty article, as long as all the anodes are electrically connected, i.e. wired together. Using more than one anode speeds up the electrolysis, and you won't have to move and turn your rusty piece during the process, but use whatever is easiest for you. You can also do more than one rusty article at a time, as long as- you guessed it- they are electrically connected to one another and nothing touches.
Step 4) Connect the BLACK clamp of the battery charger to the rusty article, and the RED clamp to the steel anode, and turn on the charger. You can use an extra alligator clip jumper if that makes a better connection to the piece than your regular clamp.
Turn the battery charger on and check the ammeter to see whether or not its “charging”- if not, you may have to scrape a clean spot in the rust so you make a good electrical connection.
Let 'er rip!
Step 3: Making the Magic
You will see bubbles start to form almost immediately, and an ugly rusty sludge will collect on the surface- all normal.
Every so often, turn off the charger and lift out your rusty piece to inspect how the rust removal is going; take this opportunity to turn or invert the piece if you are using a single anode, to make sure all parts are getting blasted.
The length of time you will have to leave your rusty article will depend on how rusty it was and the amperage of your charger. It will probably take a few hours, maybe overnight to totally remove the rust. It won't hurt anything if the charger continues to run, but it won't help either.
You can dump your rusty, sludgy water on the garden, or save it for your next rust-removal project. * note; if you used a stainless steel anode, you may have generated some semi-toxic byproducts; better to not dump this down the storm drain or into your vegetable garden.*
Step 4: Yes, You ARE a Genius;
When you remove your work piece the final time from the solution, you will have noticed that instead of rust, your piece is now covered in a sooty black oxidation layer. The easiest way I've discovered to remove this is with 3M Brand GRAY Finishing Pads, available at Lowe's in the sandpaper aisle, but if you need a more polished surface, you may have to work with the softer white scrubbies. It only takes a few minutes to remove the black stuff.
And voila, you have resurrected Granny's Dutch oven with the expenditure of just a little bit of money and the time it took your cauldron to do it's bubbly electrolysis magic.
Take a bow!