Project 1 from DaveO: electrolytic rust removal

[DaveO]

You can use electrolysis to remove rust from iron or steel. The process uses a small electrical charge to break the bond between the iron and oxygen atoms that comprise rust.

What you need:
~ an automotive battery charger, 2 amps or greater, preferably with an ammeter
~ a non-conductive container
~ sodium carbonate, commonly found as “washing soda” by Arm & Hammer. I got some online at SoapsGoneBuy.com but you can also use baking soda.
~ an anode: a piece of unpainted iron or steel to provide the electrical connection from the battery charger to the electrolyte fluid

Remove any oil / grease / dirt from the rusty part. Use a tablespoon of washing soda per gallon of water, and mix up enough to immerse the rusted surfaces of your part in your container. Clip (or electrically attach) the black/negative lead of the battery charger to the rusty part; clip the red/positive lead to the anode. The rusty part (the cathode) and the anode should not touch, but instead should be separated by 2 inches or so of electrolyte fluid.

The process works best when the anode’s surface is parallel to the rusted part. You can get creative by using an anode that bends to match the contour of your rusty part. Surface area and line of sight are key.

Turn on the battery charger: the ammeter should indicate a flow of electricity and bubbles should appear on both the anode and cathode. Time required in electrolysis depends on how bad the rust is. You may need to rotate the part to give it line of sight exposure to the anode.

The rust will turn from orange / red to grey or black; you can remove this with a scotch brite pad. Paint your part or take steps to avoid future rust.

Notes and warnings:
~ Do this in a well ventilated area: the bubbles on the cathode are hydrogen gas and generated in minute quantities, but why risk a hydrogen accumulation (and the associated explosion and fire)
~ You can reuse the electrolyte fluid. Some people discard it by pouring it on the lawn, saying it is beneficial because it is rich in iron.
~ Keep copper connections on the battery charger out of the electrolyte, or else they themselves will erode and cause additional rust on your part.
~ Web sources say do NOT use stainless steel as the anode, because it creates toxics in the electrolyte that are illegal to dump and can cause skin problems / cancers.

Why would you do this?
~ on small or intricate parts, or when typical methods are impractical
~ to remove as little of the original finish as possible, or where presence of scuff marks from sandpaper, cup brush, wire wheel, etc. is not acceptable
~ in a restoration or art project, you might leave the grey / black residue on as a patina to enhance the visuals (conditions permitting: the black / grey is often porous iron, and rusts quickly)
~ annoy your spouse / stupefy your neighbors (people around here are easily impressed, as proved by the availability of organized adult kickball leagues)

Photos:
~ The setup: my battery charger, connected to a length of angle iron as anode and rusty bolt cutters as cathode
~ “Before”: my rusty bolt cutters
~ “After”: clean bolt cutters, after an hour or so in the process. This was probably too long, could have been 30 minutes or so.

[chadford]

I just sprayed a neighbors old rusty tools with sili-kroil last night while working on his mower. might try that on a couple of them. What is a good amp number or just 2 inches does the trick?

I hear ATF and acetone 50/50 mix will break a rusted bolt and is cheap. Better than most store bought brands.

[DaveO]

My battery charger gives me the choice of either 2 amps or 12 amps, so I just figured "more power, scotty" and set it to 12 amps.

I read about mixing antifreeze and acetone at 50/50 to make a penetrating fluid, too, supposed to be better than store-bought. This electrolysis process is more about removing rust than freeing up rusted bolts.

[chadford]

My battery charger gives me the choice of either 2 amps or 12 amps, so I just figured "more power, scotty" and set it to 12 amps.

I read about mixing antifreeze and acetone at 50/50 to make a penetrating fluid, too, supposed to be better than store-bought. This electrolysis process is more about removing rust than freeing up rusted bolts.

I will try it.

The penetrating fluid is automatic transmission fluid and acetone in case you try it. I saw it on a machinist forum and it was done by a college I think. It beat them all. SiliKroil barely beat liquid wrench and WD40 did not score to good. or get a torch out.

I like the electrolysis project you did and will try it then coat the tools.

[DaveO]

Cool, hope it works out for you! It's fun and interesting, if nothing else, certainly queter than a cup brush on a grinder. Let us know how it goes.

[notabiker]

And you know I think you can plate something the same way by switching around the + and - cables. Whatever the other metal is in the fluid will transfer to the other one thus plating it... At least that's how I think it works Some gold plated pliers anyone??

[I_Love_Plasma]

Dave,
You cant let the hydrogen go to waste! Light it!

notabiker,
Yes that is how it's done. It's a little more complicated than just switching the polarities around. Here's cool video by "How It's Made" http://www.youtube.com/watch?v=ctL6Oc0STUU

[jerky]

we used to do this at my old shop and it works good.

[DaveO]

You cant let the hydrogen go to waste! Light it!

Not for me, thanks. You know how they say to let a car battery vent because hydrogen can build up? I had one flash once, ripped the top of the battery clear off. Not likely enough generated by this electrolysis process, but who needs to walk around explaining their complete lack of eyebrows?

[I_Love_Plasma]

but who needs to walk around explaining their complete lack of eyebrows?

Oh man, been there done that. Happens about four times year

[redbeard]

Oh man, been there done that. Happens about four times year

ILP = Adam Savage?

Not for me, thanks. You know how they say to let a car battery vent because hydrogen can build up? I had one flash once, ripped the top of the battery clear off.

I had one blow on me too, hit the key and heard a nice robust POP from under the hood. After seeing the entire engine compartment drenched with acid, I pray that I'll never witness one up close in person.

[hooda]

I would like someone to explain how to apply the technique to maybe the rust on the floorboards of my pickup? Doingit as explained would require one BIG non-conductive container. Seriously, could a person possibly have a sponge soaked in the soda solution, with the cathode on 1 side of the sponge, and the part to be de-rusted as the anode? Possibly worth a try.

[Tritium]

Just use a rust converter (paint on) product for that application would be the easiest solution.

Thurmond

[redbeard]

Just use a rust converter (paint on) product for that application would be the easiest solution.

I've used Rustoleum's Rust Reformer before and found it works quite well. I didn't even realize they have a rattle-can version until I googled it just now.

[ogorir]

vinegar works really well for de-rusting small parts, too. I've been using the high-strength 9% and a bit of dawn in a HF ultrasonic cleaner recently and it will de-rust and lightly degrease nuts and bolts in a few cycles. you really have to wash the vinegar off well at that concentration, though, as if you leave any on, it will start rusting immediately.

if you leave them in too long, they'll grow a black coating that's not really attached, but is difficult to remove. it will also remove all zinc plating if you leave them in overnight.

if you're less inpatient, you can use a lower concentration of vinegar and get similar results, but it takes longer. the ultrasonic cleaner is the key, though.

some of the guys on the HAMB use molasses, but I haven't tried it yet. the results look promising. at least one guy has used it on an entire frame.

[Tritium]

If you can soak the item then 10% black strap molasses and water work great, a little slow but very well.

Thurmond