Sunday, October 19, 2008

Removing Rust With Electrolysis

**NOTE: While my shop is pretty much electron free woodworking, this post is all about using electrons directly. Ironic, no?**

I was telling a friend and co-worker about my experiences using electrolysis to remove rust from tools and thought it might be time for a post on this subject.

But before I get started let's just clarify a few things:

1. I am NOT claiming to be an expert on this, but I have had quite a bit of success with this method. Most of this I learned on the Internet - but as far as I know, the "CAT Scan" set-up is my own idea.

2. Be careful - this does involve electricity and water and it gives off hydrogen and oxygen gas. I recommend doing this outside. (Which in Alaska, makes it a summertime only activity, so obviously these pictures are not current - actually, judging from the shop in the background, they are even older than I remembered!)

Okay, let's get started. For this example we will be using a Stanley #65 low angle block plane. Here's the before and after shot:

I probably should have taken pictures of a more dramatic de-rusting. This tool was not too bad to start, and I could have simply went at it with some steel wool or sandpaper. But, the difference is that with electrolysis, you don't hurt the tool at all. No abrasion, no lost of metal (pitting will still be there however). It is a little like magic when you wipe it off after its bath.

You'll need:

Rusty tool
Sacrificial iron or steel
Car battery charger with ammeter
Assortment of alligator clips/leads
Non-metallic tub
Washing Soda (Baking Soda works too, just not as well)

Here's how it works in a very general way. The tool and the sacrificial metal are attached to the UNPLUGGED battery charger (Important! tool = negative, sacrificial metal = positive) and placed in a tub of water that has an electrolyte (washing soda) added. When the charger is plugged in and turned on, the electric current flows between the tool and the sacrificial metal and a lot of cool scientific stuff happens! Basically, some rust on the tool is physically blasted off by the bubbles of gas coming off the surface and the rest of the rust on the tool is converted back into another form of iron. While this is happening, the sacrificial metal is, well, sacrificed in a slow and painful (okay, not really...) way as it somehow erodes into the water. Also at the same time, oxygen and hydrogen bubbles are, well, bubbling up.

Now you know why I don't teach science! If you are interested in the exact science of it all there are a ton of sites on this that explain it much better than I do - just google "electrolysis rust removal" and start reading. But seriously, whether you understand it or not, it still works!

On a more pragmatic note, here are some things to keep in mind:

1. Keep an eye on the ammeter - not enough current and the process will take forever - too much current (red zone on meter) and you might fry something.

To increase current either add more washing soda or move the tool and metal closer together (Unplug First!)

To decrease current either add more water or move the tool and metal farther apart (Unplug First!)

2. If the bubbles slow down, but the tool is still rusty, take it out (Unplug First!), wipe it off, and restart.

3. The process is "line of sight", which means you will either have to be patient and rotate things around, or be impatient (like me) and get creative...

4. If the water turns green and foamy, RUN! Just kidding, it's normal.

5. When you take the tool out it will start to rust again. Fast. No really, FAST! Be ready to dry and oil/wax it.

To help deal with my impatience I created a "CAT Scan" rig that placed the tool inside a tunnel of the sacrificial metal.

Here's the carrier board that holds the tool parts. It has holes drilled into it to allow zip ties to be used to secure the parts (you do not want them coming into direct contact with the other metal). These holes also allow the current to get to the bottom of the parts.

Now the carrier board and attached parts is placed into The Fully Adjustable Tunnel of Rusty Doom!TM The vertical "tail" on the tunnel allows the battery charger jaws to be clear of the water (so as not to participate in the sacrifice below the surface).

Each part is wired up to a short jumper bar which will be connected to the battery charger (again, out of the water).

And here is a shot of the rig up and running on the back deck.

A last couple of before and after shots.


  1. Dude, that is awesome! This looks a little too Dr. Frankenstein for me, but I might consider it in the future!

  2. eric -

    That's Dr. Fronkensteen! Fronkensteen!

    It's not as crazy as it looks, and certainly can be done much simpler than I show it. I have rather a gift for making things more complicated than they need to be...:)

    In my opinion, where electrolysis really shines is with very heavily rusted items (even more so if the item is of complex shape and therefore hard to clean otherwise). Of course it takes longer, and you might need to find or make a clear spot for good contact with the electrode, but it can really bring things back from the dead. Hmm. Frankenstein…

  3. Another awesome post, Dan!

    It's okay, because these are Free Range electrons, just being allowed to do what electrons like to do. Once they are in the water, they could leave if they wanted to.

    Just to clarify, in your Fully Adjustable Tunnel of Rusty Doom!TM, the hose clamps are the sacrificial metal, correct? I always think of hose clamps as something other than plain steel, like stainless, or chromed, or something. I guess they aren't, or else it doesn't matter.

    Hmmm...entire car..swimming pool...


  4. Josh -

    Thanks for explaining about the electrons - I feel much better now!

    As for the hose clamps, you are correct on all three counts: they are part of the sacrificial side of the equation, they are stainless, and it doesn't matter. In fact, the stainless lasts much longer than the regular steel. If you look closely (click to see full size) at the first picture of the rig, you can see how much more rust is on the vertical bar at the far end of the tunnel, which is the same age as the clamps.

  5. Extremely cool stuff, and the difference in the before and after is amazing.

    Thanks for sharing.

    (OT, but do you get to pick the nature of the words that pop up for verification? What with your post on e-, my verification word is "angstrim". Okay, misspelled, but still.)

  6. geemoney -

    Glad you liked the post. Nope, I don't get any control of the verification words, but that is a pretty cool idea! Maybe Blogger will think about it?

  7. I noticed you had stainless hose clamps as your sac. metal. I've read quite a bit about that combination producing a highly toxic solution that should not be disposed of improperly. I just use bendable rebar for my de-rust operation. p.s.- I just found your site and am enjoying it. Thanks

  8. Matt - Thanks for the heads up on the stainless steel. I'm glad you are enjoying the blog.

  9. Great blog, I'm really enjoying it. Can you tell me how to tell the difference between an old (good) and new (not good) Stanley 60 1/2 block plane on ebay? Or can you point me towards a website that can? Is it appropriate to ask questions like this on a blog?

  10. Matt - Thanks, I'm glad you are enjoying the blog. I don't have a problem with that question - but I am not sure I can really answer it. First, I'd recommend learning all you can about the 60 1/2. A great place to start would be Patrick's Stanley Blood and Gore
    Then, it's just a matter of carefully reading the eBay post, scrutinizing the pictures, asking the seller any questions, and then rolling the dice.

    Sorry I can't be of more help - good luck!

  11. Great site! Could you possibly share how long it took to de-rust the example. Was this a few minutes, hours, day(s)?

  12. Anon - The time depends on several factors: amount of rust, level of electrical current you create (amps), and whether you need to rotate the object etc.

    For the plane in the post, I think it took less than an hour.

  13. Dan nice approach with the Tunnel idea. I feel I must point out that using stainless steel is a VERY bad idea.

    The main problem with using it is the hazardous waste it produces. Stainless steel contains chromium. The electrodes, and thus the chromium is consumed, and you end up with poisonous chromates in your electrolyte. Dumping these on the ground or down the drain is illegal. The compounds can cause severe skin problems and ultimately, cancer. Hexavalent chromate is poisonous. These compounds are not excused from hazardous waste regulations where household wastes are.

    These compounds are bad enough that government regulations mandate "elimination of hexavalent chromate by 2007 for corrosion protection."

    Does your electrolyte turn yellow? That's a sign of chromates.

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