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Removing rust from wheel well using electrolysis

Started by polymathman, 11 December 2013, 11:13 PM

polymathman





The electrolytic removal of rust is a very old, reliable process. I watched my grandfather, 50 years ago, take an old piece of farming equipment that looked to be a lump of rust, hook some wires up, put it in a old metal bucket and fill the bucket with water and some of my grandmothers washing soda. He hooked it all up to a old car battery, made sure it was bubbling like crazy, then we went in to dinner. The next day the bucket was full of the nastiest brown stuff you can imagine. He hauled the part out, hosed it off and after letting it dry in the sun hit it with a wire hand brush. Holy cow, it was a gear head for a mower, and when taken apart, all the rust was gone from every nook and cranny. It was magic - until high school chemistry. I have used this process for many years, and I would strongly recommend that you add it to your mental toolbox. Research "electrolytic rust removal".

The California car I bought had some rust in the trunk wheel wells. We all know how and why. The left side cleaned up easily with a wire wheel and one of the 3M disks, but the right side had scaled rust that went pretty deep in all the little crevices. I went after it for a bit with the usual tools, but it looked to be a pretty long hike - cramped area with lots of metal  to be ground out. Usually I treat rust by first removing what I can using abrasives, then I use a chelation agent to kill the rust. I've used POR, which is a  treatment/paint, but I prefer RustMort, as it is a treatment just for rust. Then I go through the usual primer, filler, top coat procedure.

First inspect the area for holes. The drain was clogged and someone had poked a couple of holes in the metal to let the water drain out. Clear the drain and then fashion a way to plug it back up. Seal up the other holes. There was also a hole where the drain for the gas filler cavity goes. I used rope calk for everything.

Next make sure there isn't a lot of oil or grease on the rusted parts, as it will insulate the metal. Solvent and paper towels, or just hose it down with spray brake cleaner. I didn't need to do this.


     
Anode. I used a piece of scrap steel, probably 1 1/2 x 12 (38 x 300mm) with one end bent up so I could hook the wire clip to it. Take your time and dry fit it all together. The anode must hang free, not touching the metal in the wheel well, but as low down and as equidistant as you can. I used some string and a couple of boards. It took longer to write this than it did to set it up.

Solution is tap water with an ingredient to make the water more conductive and slightly alkaline. I prefer washing soda (at your grocers in the laundry area), but I have used baking soda with good results. I used about 3 gallons (12 L) of water to fill the well up past the worst rust, and I used 1/8 cup of soda (which was probably a bit too much.)




The power source is a battery charger set to 12v, 8-10 amps is more than enough. I watch the ammeter to track the progress. Polarity is critical. My grandfather told me to remember that negative went to the one you wanted to remove something (rust) from.  Polarity is critical. Attach the positive red to the metal bar (anode) and the negative to the body. Polarity is critical.

How to make your trunk explode. The gas released in this process is hydrogen, which is flammable, but not poisonous. For a pretty impressive explosion, leave the charger in the closed trunk for a good while, then open it quickly and unclip one of the 12v leads to give a spark. To get it just right, look up stoichiometric, or contact my uncle "One-Eyed Clyde." But if you leave the trunk open and unplug the charger from the wall, this will be impossible, as the gas isn't produced in a large quantity and it dissipates quicker than roaches when the light's turned on. Seriously, other than being what was used to fill the Hindenburg, the gas is harmless. Word.

So everything is ready. Pour the solution into the wheel well until everything is covered. Make sure your anode is clear of the body, plug in the charger, and off you go. Expect the current to shoot over to the 8 amp range and some bubbles to start forming. If the meter pegs, you probably have the metal bar shorted to the body. After a short while you will see bubbling and the really nasty looking brown scum will start to form on the top of the water. About now you will realize that there is a leak coming out the bottom onto the floor, and you need to have a drain vessel down there sooner than later. Although the solution looks like bubbling radioactive waste, it is harmless (water, soda and dissolved rust).

I ran the process for about six hours, and probably should have gone a bit longer, but you can go much longer (within reason), as the base metal (steel) isn't harmed or eroded - just the rust. Look it up. After a couple of hours the current rate drops gradually and usually stabilizes around 2-4 amps. All is well.

Shut everything down and remove the anode - extremely nasty looking. Pull the drain and let it all run out. Steal a washing brush from the kitchen and some spray cleaner. If you are outside, use a light flow from a hose. It all cleans up pretty well. The black residue is called smut - again harmless. Wet brush off what you can, and it comes off really easily when it dry. I used a shop-vac to suck all the water out of the cracks and crevices. Let it dry well.
A wire brush will clean all of the smut out, and what you should have remaining is clean, bare metal with no rust.

If you still have rust, mix up a new solution, clean off the anode and run it again. About half of the time I will do this, just for the hell of it. A fresh solution and less gunk will get the last of it.



I was very happy with the results.  Only the rust was removed, every bit was gone from all the pits and cracks. It would have been pretty much impossible to get it out any other way - abrasives would have involved much more time and a significant amount of metal removed, without the surety of getting it all.

Although it sounds dreadfully complicated, it's pretty simple. Practice on some of the rusty stuff we all have around. The bulk of the time is spent drinking beer while the whole shebang bubbles away.

This is a simple, safe and time tested method of rust removal. Like all chemical reactions, there are many factors which must be known and controlled. Variables such as temperature, solution strength, voltage and current density, and the composition of the anode should be taken into consideration.  Or you could just wing it - that's what I usually do. Regardless, further research and understanding is left to the reader - investigate the vast internet resources available on this subject. With skilled use and experience, large amounts of rust can easily and thoroughly be removed from many areas, including footwells. And of course, you can clean smaller parts in a bucket - just like my grandfather.
190sl 1957 rusting away
250S 1968 long gone
280SE 1976 got hit, parts
280SE 1979 running fine
C320 4Matic 2005 for wife -Mercedes after MIT

adamb

Thanks for the nice write-up. I can't see any pics due to firewall issues. Why not upload the pics to the gallery? That way the pics will last as long as your article.

ptashek

Just make sure you never, ever, use this process on structurally important steel elements. Two words: hydrogen embrittlement

Oh, and don't use stainless steel as electrodes unless you are in the business of super-toxic waste disposal.
Stainless steel anodes will produce hexavalent chromium in the process, and that stuff is just horrible (both for your health, and the environment)
1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE

KenM

Excellent work, thanks for posting the pics. Sure came up pretty well, I'll be using this one for sure at some point.

etmerritt33

Your post inspired me to research and to try this. Got a PC power supply wired and ready. Only one hardware store in Richmond had the A&H washing soda. Also, ordered some carbon rods (5 for $ 12) to use for anodes. Looking forward to being able to de-rust small car parts with this process. After a successful test I want to clean my 280E battery tray prior to painting. Thanks for the post!

Marc23

Hello Everyone,
I am in search of the best rust inhibitor product to effectively treat my metal objects. Having used the product rust converter(https://www.cortenplus.com/products/rust-converter), I am wondering if there are other options that are more effective.

Therefore, I am reaching out to you today to gather your recommendations. What are the most effective rust inhibitor products you have used? Which ones would you recommend in terms of rust prevention and treatment?

Your experiences and advice will be highly valuable to me. Thank you in advance for your contributions!

Best regards,

ptashek

In Europe we have this stuff called Fertan. Not sure what's in it, but it chemically converts rust into an inert substance, and leaves a layer of zinc phosphate on top for added protection.
1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE

BCK1963

Hello,

Fertan contains tannic acids (organic acids which are, e.g. applied in leather treatment) which form a complex with iron on the surface of the treated section. It apparently loosens and removes rust but doesn't convert rust dispite its reputation as a rust converter. It needs an additional primer layer before paining.

To me as a chemist the process of rust conversion is still a bit of an alchimist's magic, even though there are apparent successes and positive tests. My recommendation would be to apply any rust converter  only on superficial rust. Deeper reaching rust canals will not sufficiently be reached by the fluid.

   good luck    Bernd
Bernd

1976 Merc 6.9   Magnetit blue

ptashek

Isn't it sufficient to cut-off the oxygen supply through exposed areas? Rust formation isn't a self-supporting process, right?
1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE

BCK1963

oxygen suppy is one aspect of several.
Unfortunately paints are not tight to oxygen diffusion, means that slowly but surely oxygen will diffuse through the paint layers and support further attack.
The presence of humidity, even worth acidic humidity, s a bigger problem.
Oxygen needs water as a catalyst for corrosion to occur. That's why desert area cars are usually in a better shape in terms of rust: dry oxygen attacks metal significantly slower.
Since rust converters or removers are often acidic, it is very important to remove the acidic liquid entirely before applying a protective paint layer. Any residuals in capillaries in deeper reaching rust canals are detrimental.

Some time ago I had the air filter unit of my former Cadillac powder coated. The workshop didn't do the initial step of paint removal mechanically by powder blasting but by chemical paint removal. The lower single-metal-layer air filter body came back ok but the lid very soon showed bubbles: It consisted of wrinkled layers, which residuals of the picklng liquid were trapped in and quickly promoted corrosion.
This is similar to rust conversion which is conducted incorrectly.
 
Bernd

1976 Merc 6.9   Magnetit blue