Rust Electrolysis

Electrolysis, before and after

Electrolysis, before and after

When I decided I wanted to start restoring old woodworking machines and handtools, one thing became clear after poking around the internet: I needed to learn how to do rust removal via Electrolysis. No, this has nothing to do with hair. This is the tried and true chemical/scientific/mystical/magical way of literally turning rust back into iron. Sounds like alchemy? It is. But unlike the arcane days of a distant past where no one was ever successful turning iron into gold, this really works! You CAN turn rust back into iron.

There are many websites out there that discuss electrolysis for rust removal, so I’m not going to go into too much detail on the science or the process. These are just my notes and a couple examples of what’s possible. Electrolysis is way easier than you think. I was intimidated at first – it sounded complicated because most websites use big scientific terms. However, the one site I did follow which boiled it down quite well was Rick’s Woodshop Creations. Rick cover’s the how’s and why’s quite nicely.

Why Electrolysis?

Simply put – it is *the* least destructive method of removing rust. All other methods involve some sort of damage to the underlying good metal. Using abrasives is one such example: you use abrasives to cut through the rust until you find good metal. In most cases this involves removing some good metal until all the rust is gone. Electrolysis is the best way to keep the original metal intact, as well as not loosing much of the “rusted” metal which electrolysis recovers.

Note however, electrolysis will not fix pitting. When metal becomes pitted the iron is actually lost and cannot be recovered. Oxidized iron that is still “attached” at the molecular level can be “un-oxidized” and turned back into iron by electrolysis, but iron that was been lost due to pitting cannot be “regenerated”.

Keep it Simple

Here’s a few notes on things I found useful for this process. Again, I’m not typing up detailed directions here – I would use Rich’s site above for that.

  • Safety first. The electrolyte in the tank, the anodes and the restoration piece are all electrically “live” while the battery charger is plugged in – don’t touch any of them without first unplugging the battery charger. With a small 12v, 6 amp charger the most you will get is an “ouchie”, but some people have done this with industrial high-voltage 100 amp chargers – this is death. Be smart, be safe.
  • More Safety: once plugged in, the reaction causes the electrolyte to “bubble”, much like soda fizz – this is Hydrogen Gas and is EXTREMELY FLAMMABLE. Think “Hindenburg” – put your spooge tank outside, away from structures, and give it adequate ventilation. I doubt a bucket-sized tank would give off enough Hydrogen to be a danger, but enough could accumulate over time to be a hazard.
  • For the record, I’ve heard the electrolyte solution is fairly alkaline and may irritate your skin. Most advocate gloves. I’ve never bothered mostly because I never stick my hands in the tank. I’ve handled wet items, and never had a problem (yet) – just wash your hands when you’re done handling anything that has been in contact with the electrolyte.
  • If it will fit in a bucket, use a bucket. Some sites talk about complex bins and containers special bought for this purpose. We all have plastic buckets lying around. And when I outgrow my plastic bucket I’ll graduate to one of my plastic garbage cans. Don’t go buying a special container for this purpose. Just make sure whatever you use is plastic.
  • Iron rebar – cheap, easy, safe, works. No need to find special iron or weldable steel sheets. Yes, surface area of the sacrificial anode is important, but rebar seems to work just fine. It’s like $0.75/foot at Big Box stores – orders of magnitude cheaper than any sheet metal I’ve seen, and considering it will get sacrificed (eventually destroyed) in the process, cheaper is better.
  • Stainless Steel anodes – the jury is out on this one. Some say it produces chromate byproducts that are dangerous and illegal to dump. Others say no one has ever proved this. Unless grandma gives me a stainless steel cookie sheet for free, I’m not buying stainless steel just for this purpose. Rebar is way cheaper. And even I did have SS, I would avoid using it simply because of the *potential* environmental hazard.
  • Connect multiple rebar anodes with scrap copper wire. Don’t bother with extra jumper cables, etc. Just get a length of copper wire, strip off about 6 inches of insulation if it’s not bare ground wire, and wrap it around the top of the rebar. Make sure you keep this copper out of the electrolyte.
  • My Setup

    My Setup

  • Get a battery charger, or jumper cables that have steel alligator clips – NOT copper. I don’t know if this is fact or fiction, but supposedly you don’t want any copper in the electrolyte. If you have alligator clips made out of some ferrous metal, you can attach the clip directly to the piece you are restoring and put it right in the electrolyte. Other sites talk about attaching lengths of steel chain to the piece so you can conduct the electricity through the chain down to the piece without getting the alligator clip wet, etc. Bah! Too complicated.  Get steel clips, clip the negative (BLACK) clip right to the piece and put it right in the electrolyte, wire and all. I have a 12volt, 6amp charger that I use for my lawn tractor – it has steel clips attached to the leads coming right out of the charger. (Note: I recently noticed that the steel clip is connected by copper wire (duh). Only a tiny amount of copper is exposed at the end of the line, and this copper has been in my tank for a week. I don’t see any issue…)
  • If you want to do multiple pieces, use some steel Pony spring clamps and connect them with a steel coat hanger. Connect the negative lead to the coat hanger.
  • Make sure you get the polarity right! For the first 5 minutes of my first experiment I had it backwards. Cleaned the rebar and made my piece look even worse. It also oxidized my steel alligator clip pretty bad. Here’s how I remember it now:

RED = Rusty. Black = Iron. These are the results you want, so the Red (positive) gets connected to what you want to end up rusty, i.e., the rebar. Black (Negative) gets attached to what you want to make black: the piece you are restoring.

  • Remember to rotate the piece you are restoring. Electrolysis is “line-of-sight” for the most part – if the back side of your piece does not have line of sight to the rebar anodes, it will not be de-rusted. Every hour or two, turn your piece a bit so you de-rust the entire piece.
  • Remember to periodically clean your rebar. Every few hours I disconnect the power, pull out the rebar, and brush the crud off them with a wire brush. This helps the reaction along, making sure fresh, clean iron rebar is exposed in solution.
  • You cannot over do it. Electrolysis is self-limiting. When there is no more rust on your piece, the reaction will simply stop – bare, clean, un-rusty iron is not affected by electrolysis. I left the axe head (below) in a live solution (charger turned on) for over 24 hours – it won’t damage the piece.
  • When electrolysis is complete, your will have black areas on the piece: This is iron oxide, a byproduct of the reaction. Wash the piece in hot water and soap, and use a grey, or white Scotch Brite pad to remove this “black dust”. Hey, didn’t I say electrolysis didn’t involve abrasives? I did. But you are not abrading off rust here, you are removing a fine layer of black oxidation. Also, grey or white scotch brite does not have enough abrasive to actually cut bare iron – so it will leave the piece clean and polished. If you wanted to remove rust with a grey or white scotch brite you’d have to work at it for days, if it would work at all.
    Did you know that Scotch-Brite comes in different grades identified by color? Check this link out for for a great explanation of the various grades of 3m Scotch-Brite.
  • A freshly cleaned piece is highly susceptible to “flash” rusting. After you wash/polish the item in hot water and soap, immediately dry the piece with a paper towel and spray it down with BoeShield T-9 or WD-40 to give it a measure of protection against re-rusting. Some poeple also like to wax the piece. Your choice.

Some examples

DSC_5434At the beginning of this post there is a picture of an old DeWalt two-wing tongue cutter, circa 1950’s. It was sitting in a box of rusty “stuff” that I got with my DeWalt GS. I wasn’t particularly worried about damaging this piece and wanted to try out electrolysis before I used it on something important. This is also a fine example of a piece that would be difficult to de-rust using abrasive means: It’s irregularly shaped, and more importantly, still SHARP. Trying to abrade rust from a sharp instrument is asking to get sliced. The picture to the right is another view. I’m very pleased with the results.

DSC_5443After the two-wing cutter, I wanted to try something “larger”, so also in that large box of stuff was a beautiful old head from a felling axe. It’s a huge head, as far as axes go: about 8.5″ x 5.5″, and heavy: 4 pounds. I had to suspend this in the spooge tank with some twine due to the weight. Because electrolysis is “line of sight” it was hard to de-rust the eye of the axe. I kept having to turn and cant the head to give line of sight into the eye. This has a big “wow” factor though, the difference before and after is amazing. Once I sharpen this badboy on my Tormek and get a nice hickory haft, it will be a pretty sweet axe.

DSC_5456Another item from the box of “stuff” I got with my DeWalt GS, this is a wonderful old Delta 3-wing cutter head. These were made in the 1930’s and are some of the best molding heads ever made. Corob Cutter still makes knives in 48 different profiles for this head, and original Delta-Milwaukee knives can still be found in various places on the net.



I also inherited a few toolboxes full of rusty machinest’s tools from my father-in-law. There is so much great stuff in those toolboxes, but here a few items I cherry picked to restore once I saw how well electrolysis was working.

DSC_5452These are nice old Brown & Sharpe machinist’s try squares.  I really wanted to restore them and put them back into service – I know my father-in-law would have liked that. It was difficult to get all the black oxide off these, but some prefer this “patina”. They sure look a lot better than they did, and I like the patina – gives them character.



DSC_5467This (front and back) is a Starrett No. 603 6″ steel rule. At first glance of the before pictures one might think it was beyond hope. After 10 hours in the spooge tank, all the rust was gone. Electrolysis will also loosen up old paint, so the green and white paint stuck to the ends bubbled right off. This is a double-edged sword though, as you don’t want to loose good paint, like the black japanning(?) of the numbers and graduations – so go slowly and be gentle with the final scrub. Unfortunately there is some minor pitting that is beyond repair, but this is still a reliable precision instrument that will be put to good use.


DSC_5481Here’s another one: a Starrett No. 607R 6″ steel rule. This one came out awesome! The 607R has one edge that is graduated in 1/100ths – the picture does this edge no justice. Those 100 tick marks are as sharp and crisp as the day it was made.




DSC_5469This was one of my father-in-law’s spring calipers. There are several of these in various flavors that I’m going to restore. This one is marked “Union Tool Co. Orange Mass U.S.A.” We’re trying to figure out whose initials are inscribed on it because they’re not my father-in-law’s.  This has a really nice patina that I like.

One Response to “Rust Electrolysis”

  1. Peter Jeans Says:

    G’day David

    Stumbled into your site re electrolysis (I’m fooling round with it as we speak). Liked your explanations. Was struck by your Starrett No. 607R and its 1/100 graduations. Would love to see that.

    Trouble is, the greater the graduations per unit, the less accurate the read-out will be; somehow, the width of the black graduating marks has to be accounted for. The ideal marks are those that aren’t there. Hmm….

    Cheers from Oz – Himself.

Leave a Reply