Electrolytic Rust Removal Leaves Your Parts Shiny As New

If you’re tired of removing rust by hand, you’d be surprised how easy it is to build your very own electrolytic rust removal system!

[James Taylor] is in the process of restoring a very old lathe. Most parts were small enough to simply remove the rust, paint, and grease via chemical stripping and bead blasting, but he ran into a problem with the 40kg lathe bed. It’s painted and if he chemically strips it, he needs to rinse it — which might result in even more flash rusting.

He looked up electrolytic rust removal, and was a bit suspicious of how simple and effective it claimed to be, but he decided to give it a shot anyway. He picked up a big 160L rain barrel, 6 pieces of rebar, some copper wire, and a computer power supply.

The process is simple. Add some soap flakes, fill the barrel with water, and dangle your item to be cleaned inside the solution. Connect the power supply to the rebar (positive) and your part (negative), turn it on, and wait for some bubbles. The rebar acts as a sacrificial material and you will create hydrogen and oxygen gas as the reaction occurs. For a part this large, you probably want the system outside or in a well-ventilated area.

It’s still not done yet, but [James] can already see the paint on the metal flaking off and rust clearing up.

82 thoughts on “Electrolytic Rust Removal Leaves Your Parts Shiny As New

    1. Nah, it takes the paint off as well. Grease & oil too.

      I once stripped a bicycle frame in the bathtub (yes ladies, I’m single!) like this.

      Use a 24 volt supply, and carbon rods as the anodes. The rust doesn’t stick to the them (unlike metal) so the current doesn’t drop. Otherwise give them a clean every so often. Or don’t worry about, it’ll finish eventually.

      Leave it as long as you like, as the rust comes off the part the current will drop, leaving it for too long doesn’t do any harm.

      It’ll flash rust when you take it out, use phosphorus to stop that. Makes the new paint stick better anyway.

        1. Phosphoric acid reacts with rust, it converts the red stuff into black stuff. The black stuff (Fe3?) prevents further rusting.

          That’s what’s in rustoleum etc, and the better metal paint primers.

        2. Like Tony says, there’s red rust(hematite, Fe2O3) and there’s black rust(magnetite, Fe3O4) and some combinations of the two. Bare metal is Fe(0), the iron in red rust is Fe(III), and the iron in magnetite is Fe(II, III). The roman numerals denote the oxidation state of the metal. Roughly, the smaller the number the closer to metallic steel it will behave. Since magnetite has a mix of the two iron states it’s not as flaky as red rust. So you can paint over it.

          @ Thinkerer
          You want to balance the power output to the surface area of your electrodes. There’s some optimal point so you don’t needlessly degrade the electrodes without fixing the part. What that point is I don’t know. You also don’t want to boil off your electrolyte. All that power has got to go somewhere and if it’s not going into reducing iron it’s gonna go into heating the electrolyte.

      1. Would a battery charger (sloppy 12V, 2/10/50 selectable amps) be as good or better than a modded power supply (clean 12V, modest [18?] amps)? I think more voltage is good of course, but (keeping it simple) I’ve got several car battery chargers in the garage and not fussing with yet another ATX would be nice.

      2. Given that many, many bicycle frames and components are made out of chromalloy steel, which contains Chromium, which is extremely toxic…that was incredibly, incredibly stupid.

        1. Chromium itself isn’t toxic, chromates (CrO4, etc.) are. The excess chromium can be used for electroplating later, and it can be extracted from the water (if it didn’t stay on the metal to begin with)

    1. Air humidity will still rust the everliving shit out of it.
      Unless you live in the dryest part of earth.
      So you’ll still need to coat the part with a protective compound ASAP.
      Or manhandle chemistry to your advantage so the rust removing process does that for you.

  1. A few comments if I may. You need to add an ionic compound for this to work. The most common would be sodium carbonate (washing soda). It does an excellent job removing rust without damaging the surface. but it does leave behind a black layer on the parts that can be removed with a little wire brushing. and DO NOT use a stainless electrode. it will create a poisonous Chromium compound with the water.

    1. Given enough time the rust itself should ionize the water I think? Just add a little salt/sulphuric acid to aid the conductivity of the water. A stainless anode should be safe as it’s not being dissolved in the water, no? I assume attempting to clean up a tarnished/painted stainless part would be a no-no.

      1. Never mind I read the article and saw that washing flakes = sodium carbonate. Don’t know why people would call it washing flakes as I will never wash anything with that stuff, I use it to balance the pH of my pool!

        1. > Don’t know why people would call it washing flakes as

          If you look at your laundry powder, odds are you’ll find it contains Sodium Carbonate, or Sodium Percarbonate/Peroxyhydrate (which becomes Sodium Carbonate and Hydrogen Peroxide in water).

          It’s been used in people’s laundry for… ever. Which is why it’s called Washing Soda (or Washing Flakes apparently, perhaps that’s regional).

  2. I just do what car restorers do: go to the supermarket and buy a few bottles of the cheapest vinegar (any kind) you can find. Place rusted part in and leave for a while. It’s enviromentally friendly and won’t eat your skin off like more corrosive solutions. Some people use molasses but vinegar is available pretty much everywhere.

      1. I don’t think using vinegar for a lathe bed would be too impractical at all – I’ve stripped a large fuel tank for a vintage vehicle using viniegar with perfect results. It was so big I had to use a large wheeled trash bin to fit it. It came out looking like a shiny tin can. Then I neutraized it with a dip in dilute bicarb of soda before thoroughly washing, drying and painting. As others have sugessted, compressed air is great for drying things quickly.

  3. This process is awesome! I built an electrolytic rust removal set up a few years ago and it has saved me hours of labor and a good deal of money. Be careful- the gasses produced are flammable. I keep my tank outside and it’s fun to make the bubbles ‘explode’ with sparks from my angle grinder. It sounds like small firecrackers. Any ideas on collecting and using these gasses?

    1. Should be the same concept as the H2O science experiment with the anode and cathode in dedicated collection columns. Google “H2O splitter” for pretty simple designs.

  4. I dabbled in similar things when I was younger. Only I had access to one of those cheap Chinese air-cooled DC inverter welders. You get quite impressive results pretty quick when you pump 160 amps through such an assembly. But a PC power supply is a very clever and effective option as well.

      1. hmmmm, think about that. The iron oxide—– AKA rust —- being reduced to elemental iron then ionized so that the atoms become the charge carriers which pass current from one electrode to the other where they are then oxidized again, thus relieving them of their charge means that the CURRENT is the measure of what quantity of rust is being converted how fast—- assuming that the voltage and conditions for this reaction to occur at all are in place. You should be careful how you’re talking round these parts. You’re in danger of breaking Ohm’s Law :D

        1. Mr Ohm is safe.

          It’s just just electroplating, you’re plating the anodes with iron oxide.

          Yes, higher volts gives you more amps, but at a certain point it stops being effective (it’s unlikely to have 160 amps though a bath, even if the supply is capable.).

          The term is ASF (amps per square foot) which sets the time needed given a certain surface area & current. There’s a limit to how much can be deposited on the anodes as once, above that you just create heat or other odd things, eg sometimes ‘burning’ the plating – not that we care here).

          12v is a bit low, 30v-ish is better. That’ll push more amps, but not too many. Inverter welders are around 30v-40v IIRC, so should work ok.

      2. If I remember my electrochemistry, I thought that the voltage was fixed for a particular reaction and so increasing the voltage on the power supply only matters if it results in a higher current. This is because the current is literally a measure of the flow of charge carriers, which in this case means it’s the flow of ions in the solution, which is what removes the rust. So are we saying the same thing, or do you know something I don’t?

      3. Doh!!!
        Volts =>Energy of electron; Amps=>Electrons or Ions per second (6,2*10^18). Thereby volts will generate heat, while more amps make faster reaction. But because of Ohms law, one must increase volts to get more amps. Better way to do that: dump in more ions (e.g. phosphoric acid) to get more charge carriers thereby more amps @ lower voltage

        1. It’s the amps that creates the heat, and doubling the amps creates 4 times the heat (Watts = Amps squared x Resistance).

          (It’s why cars are moving to 36v rather than 12v, you get more power with using the same size wiring, and heating in the wiring is the same because you didn’t increase the amps.)

          The ultimate limit is the surface area of the anode, decreasing the resistance of the bath only goes so far (eg dumping in more washing soda makes little difference).

      1. I too know somebody who had a small explosion using this process. I think the issue is that the washing flakes can cause the hydrogen to foam instead of just bubbling away.

      2. Yes it can, the guy posted pics of the mess it created. Depending on the container it is done in it can accumulate. Also sometimes a soap is used and the hydrogen fills the bubbles which do not dissipate.

  5. For a truly comprehensive explanation on how to perform rust removal using electrolysis, a well-seasoned machinist by the name tubalcain on youtube gives a much more detailed walk-through on how to complete the process. The polarity is very important, otherwise you will end up with all the rust collecting on the item you wish to clean, thus destroying it. The rebar that James uses is a nice touch. Check out tubalcain’s video: http://www.youtube.com/watch?v=ka6ArN_ehas

  6. On mine, I used 6 pieces of rebar. At the ends of the rebar I welded some bolts at a right angle to the rebar so that the bolts would fit through holes that I drilled in the sides of the barrel. This also made it easier to attach wires with spade lugs to make sure that the connections were good. I used a battery charger to run it. Works like a champ.

  7. Be aware that some (if not most) steels will suffers from hydrogen infiltration.
    This will reduce drastically their strength. It will also make springs very fragile.

    So ok for non stress part, not ok for springs and fasterners.

    1. hydrogen infiltration is a factor for hardened steel — things like tool steel and crank shafts — a cast iron lathe bed isn’t a factor.
      fortunately there is an easy solution for parts that hydrogen embrittlement matters:
      stick the part in the oven at 300F for a couple of hours.

  8. OK: if I have a small car chassis (59 bugeye sprite) that needs rust removed, can I literally just create a tub in my garage using waterproof tarps and a frame, drop the car into it, fill with water and electrolyte, place rebar around the perimeter, charge the car itself with the negative clamp, zap it until clean?!? Of course, dry and prime immediately afterwards. It’ll strip the paint too?

    1. The water weight would render your tarps insufficient and your garage would be very, very wet. Water + electricity… yeah. On the other hand, you wouldn’t have to worry about finishing the project. Ever.

      I’d suggest using an above-ground swimming pool and a crane. If the neighbors ask, just tell them you’re making art…

    2. One problem you get with this process is called line of sight. The electrodes have to have a “line of sight” to the rust or you get shading, areas where rust is not removed. Getting total electrode line of sight with a car shell, inside, and out, might be somewhat challenging to do. I mean it isn’t like you’re dipping parts into a magical solution, and whatever the liquid touches gets the same treatment.

      People can, and have electrolytically cleaned cars, but it is not trivial to do.

    3. I’ve seen this done. —well, actually with a truck chassis but it was larger than your car….. The fellow cut some logs in the yard and laid them out like a rectangle, then placed a heavy duty tarp over it and filled the “pool” with water and added baking soda….. Took a long time with multiple car battery chargers. But it worked great…. Also, if you wait long enough, you may well not have to worry about the “shading” others mention. The rust is removed from all surfaces exposed to the liquid, it’s just pulled off faster from those closer to the other electrode. It will still come off eventually. You can google for camping hot tub if you need help figuring out the setup with the logs and tarps.

  9. I used soda ash for my pool and a 6/12 volt battery charger and a bucket to remove the rust from the lathe I restored. My 1939 Craftsman 101 lathe cost $14.00 new. Following all this good advice I think I could bring this project in for a shade under 3 grand.

    1. How does galvanized metal have chromium in it? I mean it might, but it probably doesn’t. Galvanization is zinc. You’re not supposed to weld galvanized metal because burning zinc releases toxic zinc oxide. Although a little metal fume fever never bothered me. Plus who is going to drink the dirty vat water anyways? I used to work at a place that hard face chrome plated printing press dies and you don’t want to know what we used to do with our waste chromium. Flush! heh. We’d get chromium by the 55 gallon drum. It is these red flakes as I can recall. I didn’t stay there for too long.

      1. wow, that is fucking horrible. I hope that you all get cancer. Seriously. Have you heard of Erin Brockovich???? Chrome plating shops were the first categorically regulated industry in the US in terms of the toxic waste situation. Hey, let’s poison everyone else for money! That sounds awesome!

        Those people are lower than fucking pedophiles. At least child rapists usually only hurt a few people. And not usually are they doing it for some paltry sum of money.

        Absolutely disgusting. Laugh about it some more why don’t you?

    2. Grab the chemists and their books too, and burn them at the stake!!!

      So much fear and ignorance. This is why we can’t have nice things and nothing lasts past the warranty anymore.

      To give up chrome completely in your diet you’d have stop eating whole wheat, coffee, nuts, green beans, broccoli, spices, meat, fruit and other vegetables. Plants uptake chromates when not enough sulphates are available in the soil. At some point your body would stop being able to metabolize glucose and lipids. I’ve no idea what the mechanism that our biochemistry uses chromates, ask a biochemist, I was more interested in Organic and electrochem 30 + years ago in college.

      I’m afraid that pcf11 is correct that Galvanization is zinc, used as a sacrificial anode. it corrodes to zinc oxide instead of the iron. It’s called galvanized because it actually becomes a zinc-iron air cell producing electricity until the zinc is completely oxidized, then the iron starts rusting. One can keep a whole bridge or battleship from rusting by bolting a block of zinc metal to it. Replace as needed.
      I don’t understand why so many plating companies dumped chrome though. That’s what they made their money with, why dump your raw materials? Its insane. They needed some better chemists, and probably weren’t willing to pay them.

      One of the good things about elemental chrome, it passivates like aluminum or titanium does, a thin oxide layer that really really doesn’t want to oxidize any deeper, which is why it makes such a good plating for lesser metals. Not as good as gold or platinum, but still pretty resistant. Same as stainless steel, its pretty much happy the way it is and doesn’t want to oxidize either, plus the increase in carbides in the steel makes for other good properties.

      As for whether hexavalent chromium ions are produced…
      Actually it depends on the electrolyte used, sodium carbonate, Na2CO3, washing soda is not necessarily a bad choice for alloys with high amounts of chrome in them, providing you keep strong oxidizing agents away from the mix, like Sulfuric Acid, because that’s how chromium(IV) is made in the first place. Without such a strong oxidizer, it’s likely to remain chromium(III)

      If you suspect you’ve made some chrome salts, ammonia will change it to Chromium(III) hydroxide which is completely insoluble in water between pH of 6-9. . Keep in mind that ammonia is basic and to precipitate out chrome you want to keep the pH less than 9 and greater than 6, ideally slightly basic at 8. The chrome will drop out as a green gelatinous precipitate.

  10. Question: What is the best way to get a sacrificial anode into a tightly enclosed container, like a vehicle gas tank, with the maximum amount of surface exposed, without shorting TO the tank?

    1. Drill many holes in a small diameter PVC pipe, then thread the anode rebar into the pipe creating a porous sleeve. Line of sight to the anode through the holes but no direct metal-to-metal contact. In theory, a flexible plastic hose with holes and soft iron wire could be used instead of rebar to allow the anode to be inserted around curves through the fill pipe of the gas tank.

    2. I once used braided polyester rope and threaded a few strands of baling wire through it. If you push the ends together the braid kind of opens up like a Chinese finger trap and the wire can be threaded though. Braided sleeving would also work.

  11. Would this rust removal method damage small metal parts?
    I have a steel plate from inside a digital point and shoot camera that is rusted.
    It has many small screw holes and I’m afraid those holes will get stripped.

  12. I did my lathe “restore” (clean to bare metal and paint) with a wire wheel in a hand drill and a regular hand-held wire brush. -that’s stripped back though a hundred years of paint layers.

    I suspect that this will give better results though in certain areas, but I’d have never have found a bucket big enough to actually submerge the whole thing.

    (the lathe bed is a gap bed, that’s 5feet long with a 9 1/2inch swing if you’re English, (19″ if you’re American as we measure lathes by radius rather than diameter of objects turn-able.).

    Currently in the process of “restoring” an air compressor with a small tank, I cleaned the inside of the tank with Citric acid,

    I’m not that this guy did it the “wrong way”, but even if something is big, often times it can be better to clean it by hand, that way you’ve totally inspected the whole of the (what can be a quite dangerous) machine. and can see and repair any damage that may exist before painting over small cracks etc.

    Then I’d use either acid or an electric method to clean anything that I couldn’t get to myself.

    1. Hey Dan,

      I totally agree with you on the need to get right in there and inspect to see what needs to be done. My main issue was basically the inability to get a drill in the guts of the headstock to clean it out.

      All the other parts that I’ve done so far have either been bead blasted, cleaned with oven cleaner or paint stripper or wirebrushed. I hate to think that after all the stripping, cleaning, painting that because things were rushed and not done thoroughly that something could be missed that would necessitate doing it all again to fix it lol.

      Good luck with the compressor restore :)

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