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Why does this electrolytic derusting trick work?

Q. I have been removing rust from metal tools by using a galvanized bucket of water and suspending the tool in the water by a string. I connect a twelve volt battery charger [on eBay or Amazon affil link] to the tool and the other side to the bucket. Overnight the rust turns to black goop which I wash off and further buff out the tool. Works great. I got it from a tip in a wood magazine. Can someone explain why this works. What is the "electrolysis?" process here ? Thank You.

Dennis Slabaugh
Hobbyist Woodworker

Blackstrap Molasses

(affil links)

A. The rust on your tools is FeO, or iron oxide. When you run the electricity through the tools the electrons reduce the FeO into Fe and O2, oxygen gas. Every time an equal part of the galvanized bucket which is Zinc is oxidized into ZnO or Zinc Oxide, a white powder. So every time you do this, a little of your bucket is blown away, watch for holes! haha

Adam Hoalcraft
college student - usa


A. Getting rid of rust can cost a fortune in chemicals but if you have the time and can fully submerge the item to be de-rusted, here is a cheap way to do it. Submerge it in a black molasses and water solution. 1 part black molasses to 9 parts water. I have 40 liters of the stuff mixed up.

Descendants of the mutineers, 1862

descendants of the mutineers

Where I used to work on Norfolk Island (in the South Pacific, halfway between Australia and Fiji - the place where the majority of the descendants of the mutineers from the Mutiny on the Bounty live), we had a 200 liter (44 Imperial gallons, 55 US gallons) drum mixed so we could dip big stuff. Like any small island, because of salt spray, rust is a real problem over there.

Really severe rusting will need a week or so in the solution. I recommend removing the job after a few days and wire brushing to remove the loosened scale, a quick hose down and return to the pot for another go. It is essential that the steel is fully covered. Unprotected steel will corrode very badly at the air/solution interface where it come out of the solution. Note: Some alloys e.g., zinc will be severely corroded by this stuff so keep it for iron and steel only or test it first.

I bought 5 liters of blackstrap molasses (stuff they feed horses) from my local feed and produce store. It is quite cheap.

Ron Beckett
- Emu Plains, NSW, Australia

Multiple threads were merged: please forgive repetition, chronology errors, or disrespect towards other postings [they weren't on the same page] :-)

Electrolytic rust removal from gas tanks

Q. I am trying to remove rust from a 1930 Truck gas tank. Is it possible to use some sort of galvanic or electrolytic process to remove the rust.

Jim Butterbaugh
- Tijeras, New Mexico, USA

Q. Ditto for a 1960 Ford F-100 pick-up trick gas tank.

Marvin Koski
- Dearborn, Michigan, USA

Q. I'm interested in finding out more about electrolytic derusting of automotive sheet metal. Specifically, can anyone tell me the percentage of sodium cyanide to sodium hydroxide to use in solution and the voltage/amperage per square inch to use? Can a sodium hydroxide & sodium gluconate solution be used electrolytically without having the solution boiling? What are the best complexing and foaming agents to use?

Thanks in advance for any insight,

Jim Walters
- Victoria, BC, Canada

A. Jim,

I can answer some of your questions. Sodium gluconate + sodium hydroxide used with current is an excellent deruster for mild steel. No cyanide is needed. Main problem is that when the rust is removed there is a pit left in the surface. The derusted surface is not blemish-free. The best I can recall of the operating conditions is: 8 oz/gal of sodium gluconate, 8 oz/gal of sodium hydroxide, 140 °F and 5 Volts anodic.

Hope this helps,

Pat Mentone
Pat Mentone
St Paul, Minnesota

Ed. note: Anodic means the work is attached to the positive, as opposed to the negative proposed above by Adam H. Neither is wrong; sodium gluconate is a chelating agent which dissolves the rust.

Stripping Paint & Rust from Antique Auto Rims

Q. I am interested in constructing a small Acid bath for cleaning small Auto parts, wheels, etc. Any ideas on what's involved in these Electrolytic rust removal systems where the part is submerged in a caustic bath to remove paint then the remaining rust is removed.

Rob Wellner
- Philadelphia, Pennsylvania USA

A. Hi Rob. Pat's answer is probably apropos. The caustic eats some paints, the gluconate dissolves rust, and the electricity generates scrubbing bubbles of oxygen.

Acid (low pH) is the opposite of caustic (high pH), and I imagine that you used the term as slang rather it's scientific meaning.


Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey

Is electroplating process the same or opposite of de-rusting process?

Q. Greetings. I am in 4th year high school here in the Philippines or equal to 10th grade in US. We had our project and I did the de-rusting method using the process of electrolysis in removing rust of rusted objects, or known as electrolytic rust removal but my teacher said that the project I did does not de-rust objects, it actually covers the rust of the rusted object, in short, it is not de-rusting process but it's electroplating, the process of using electrical current to coat an electrically conductive object with a relatively thin layer of metal. How could I defend this? Please help me. Thank you so much.

Carmi M [last name deleted for privacy by Editor]
student - Mexico, Pampanga, Philippines


A. I think your teacher was trying to claim that the direction you have the battery leads hooked up meant you were plating onto your part rather than dissolving metal off of it, Carmi. But while that might be "sort of" true from a hypothetical viewpoint, because plating is done with the workpiece cathodic, actually you are correct and your teacher is incorrect!

It is true that in electroplating you make the workpiece cathodic (connected to the negative pole of the battery). Then, if you have the right operational conditions this surfeit of electrons at the workpiece can attract and reduce the positively charged ions in solution to metal and have them deposit on the work as metal (electroplating).

However, de-rusting can be done with either polarity. If you use the same polarity as electroplating (the work cathodic) and the right conditions, the rust Fe+++2O3, reacts like this:

Fe+++ plus electrons => Fe0

In fact -- although it's not foolproof and certainly not easy -- this process has actually been used to "run the film backwards", restoring corroded artifacts closer to their original condition.

You are not necessarily electroplating just because the workpiece is cathodic, nor necessarily "de-plating" just because the workpiece is anodic. If you don't have the right conditions, electroplating won't occur nor will de-plating occur -- there's more to it than just the polarity. Most every industrial plating line in the world has an electrocleaning step early in the process; maybe half are anodic and half are cathodic … and none are intended to either de-rust or electroplate, and they don't :-)

Demand an A+ !

Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey

Q. I am currently using a large tank of Potassium hydroxide and H2O to try to remove rust from steel and iron art objects/ antiques. I do not know the nuances of this process. I currently have been using a 12 volt battery charger [on eBay or Amazon affil link] as my power source. Negative on the piece to be stripped, positive on an electrode in the bath. I also have a tank of H2O and baking soda [on eBay or Amazon affil links] . If anyone can give me tips on this process or ways to fine tune it to work better let me know. I am an art restorer and have to remove the rust as gently and fully as possible. I also have to do this without damaging original plating and specialty finishes, "Bayer-Baurf" black oxide on iron and steel.

Michael Grucza
Grucza Studios - Chicago, Illinois, USA

A. Dear Michael!
If you are art restorer I think that you must know that electrolytic de-rusting cannot be used for plated objects of any sort. Second problem with this process is hydrogen embrittlement. Best process for removing of thin layers of rust is ammonium citrate(5% solution, pH 3,5). Blued or chemically coloured surfaces can be cleaned only with oil based solutions (Balistol, WD-40 [adv: item on eBay or Amazon] , petroleum).You can visit ICOM-CC metal working group webpages. Conservation Online web site is very good too.Good luck!

Goran Budija
- Cerovski vrh Croatia

Q. I've been doing a lot of reading about removing rust through an electrolytic process involving a 12 volt power source, scrap iron, and a solution of washing soda [on eBay or Amazon affil link] and water. It seems like a simple easy thing to do. But my question is what to do with the solution when it is no longer needed. I just read your information about regulations regarding electroplating and the chemicals that are used in that process. I understand that the waste generated from the rust removal process it is just dissolved iron oxide, water and calcium salts, and should be harmless? I've read where people just dump it out on their lawns and that the grass actually likes it, but I live on Long Beach Island in NJ, and I don't like the idea of dumping anything on the ground regardless of the legalities. My thoughts are, can this solution be poured into the sewer system? Or my other thought is to pour it into a shallow pan and allow it to evaporate then throw the residue out in the trash.
What are your thoughts on the process, does it work? (I know the dangers of hydronization (pardon the spelling). Is it safe to do at home, provided the area is well ventilated (hydrogen gas)? Does this fall under the same legal regulations as electroplating, after all it works on the same principle?
I don't know if this falls into any area that you talk about, but I have not been able to find this information on any of the websites that talk about this, and I would like some information that is coming from someone who is intelligent before I start posting on some of these sites.

Thank you

Joe Bree
hobbyist, and theatre technician - Beach Haven, New Jersey
September 11, 2008

A. Hi, Joe. Electroplating wastes are not regulated based on their actual hazards, but "categorically". What that means is, if it was generated by a commercial electroplating shop it's regulated, regardless of what it is. I doubt that there are any regulations covering your situation, since it is neither an industrial process nor a highly defined one, nor does it start with nor generate hazardous chemicals. And I do not see any environmental impact if you put the residue into your toilet and down the sewer. washing soda [on eBay or Amazon affil link] and iron are quite innocuous stuff for a sewer system. Good luck.

My niece was an actress at Surflight for a couple of summers a long time ago; I hope all is well on LBI.


Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey
September 12, 2008

Q. Can electroplating be used to remove rust from tools? If so how does one build a unit?

Jerald Boyd
- Prineville, Oregon USA
October 31, 2014

"Practical Conservation of Archeological Objects"

on AbeBooks

or Amazon

(affil links)

A. Hi Jerald. It's not called "electroplating" in that case, and it doesn't actually involve electroplating -- but it's the same equipment and sort of the same wet chemistry. We appended your inquiry to a thread on the subject. Good luck.

As an update to some previous responses: although de-rusting can apparently be done with either polarity, I have confirmed that the work should be cathodic (negative / the same as in electroplating) for the archeological restoration method of converting corrosion back to metal (as opposed to just removing it). I don't have this book, and haven't read it, but Amazon's "Look Inside" feature revealed that much. .


Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey
November 2014

Q. I am considering using a small vat of borax [affil link] solution with steel anodes placed around the perimeter and rusted steel parts, for a fabrication project, placed in the solution and coupled together electrically with jumpers to act as cathode(s) for rust removal. Is this in fact a cleaner or is it going to just deposit iron on the parts to be "cleaned"?

Bob Farmer
- Knoxville, Tennessee, USA
March 5, 2015

A. Hi Bob. It can't electroplate iron onto the part because there is no iron in solution. If you proceed exceptionally slowly and are exceptionally lucky, some of the rust might be converted back to iron. But in the general case, the excess of electrons causes water to separate into hydrogen gas bubbles on your part and oxygen gas bubbles on the anodes. These "scrubbing bubbles" assist in the cleaning.


Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey
March 2015

Q. I had a solution of water with electrolytic solution of sodium chloride I then had 3 iron wall plates each weighing 25 grams. When I connected the wall plates and immersed them in the solution and turned on the electrolysis machine I saw something amazing. The plates were connected and fitted well in the solution. After 1 hour, the entire jar was filled with brown sludge and I noticed that anode plates lost about 5 grams, but the amount of the solution was far more than 5 grams. What happened? I probably ended up with 2 times what I already had. I was skeptical about my measuring machine. And so I bought a new one and I got the same reading.
Can someone help me??

ishmael Izra
- Tucson, Arizona, USA
January 24, 2017

A. Hi ishmael. Please try your best to be clear about what happened before you ask people to account for what happened :-)

I understand that you had 75 grams of iron "wall plates"; you connected them as the anode; over the course of an hour they lost a total of 5 grams. I don't know what you mean by "the amount of the solution was far more than 5 grams". Are you saying that you measured the weight of the solution before and after the electrolysis and the solution gained far more than 5 grams in weight? Yes, that certainly sounds highly improbable to me.


pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha - Pine Beach, New Jersey
January 2017

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