Electrolysis - A Superior Cleaning Process

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Updated May 2004 Based on experience, recent discoveries and feedback from internet friends.

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An electrolysis primer - Introduction

One of the most tedious jobs we encounter while restoring old iron is the process of removing many layers of paint and rust as well as freeing up seized bolts and pistons. The following introduces you to a method of parts cleaning that has proven to be the most effective means of de-rusting and paint removal I have ever used.

Background

The electrolysis process has been used by achivists for years to clean metal objects. I saw a show where a 1700's vintage French brass cannon was cleaned to reveal the complete Royal Insignia, and this was after 250 years in the sea. I had alway expected it was too expensive and complex but it is not.

I can personally vouch for this process since it was used exclusively for the cleaning and un-seizing of my own engines and machinery. Anyone who has ever tried to clean up rusty iron (or any metal) will embrace this method with a passion equal to their love for the object itself.

A specific experience with this process has been recently tested when I overhauled a Type J, twin cylinder Atlantic Marine Engine. This engine was no exception to the state in which we often find our engines. The parts that were not covered in 10 layers of paint, were heavily encrusted with rust and many parts (including both pistons) were seized solid. The engine is now completely apart and clean using electrolysis exclusively and without the use of rotary wire brushes, chisels, flame heat or excessive force. And it is cheap and easy to implement and is even more environmentally friendly than the use of caustic and petroleum-based cleaners. There are no foul odors and the solution ( if you use washing soda) is not irritating to the skin.

What is Electrolysis?

For the purposes of the information contained herein, electrolysis is a process that passes an electric current through an Electrolyte, causing the migration of the positively charged ions to the negative electrode (cathode) and the negatively charged ions to the positive electrode (anode).

Simply put, if you connect a power supply to a container of liquid with 2 rods immmersed in the liquid, chemical changes occur to both the rods, which must be a metal, and the liquid, (electrolyte).

The process of electrolysis is not new, in fact it is as old as electricity itself. The same process occurs naturally when a metal in the environment is exposed to a reactive liquid such as salt. A small battery is created. Lead-acid batterys of today produce power by the process and electroplating is performed by using electrolysis. For our purposes, we are trying to remove paint, grease and rust from metal. Rust and corrosion is formed by electrolysis. We will use the same method to remove it, and more.

Electrolyte - A substance, in solution with water or another liquid, which is chemically changed by passage of electric current throught it.

The electrolyte we use and refer to is the substance you mix with water in a bucket into which you place an electrode and the part you wish to clean.

Ion - An atom or group of atoms that carries a positive or negative electric charge as a result of having lost or gained one or more electrons.

The particles of metal which travel from the part being cleaned to the electrode are in the form of ions. An atom of iron (for example), once acted upon electrically through an electrolyte, is broken away from the base metal and becomes an ion with a negative charge. It travels through the electrically conductive electrolyte and goes to the electrode since it has an affinity (attraction) for the positive electrode. At that point the ion will lose its negative charge and either stick to the electrode or drop to the bottom of the bucket. If the particle is small and light enough, it may become part of the electrolyte solution.

What can be cleaned?

The greatest success has been with steel and cast iron but essentially any metal can be cleaned or for that matter any electrically conductive material. But special caution is needed with aluminum or plated items. The process removes layers of metal at a molecular level and very slowly (if washing soda is used).

Some warnings which may not apply at this time but in the future.

"Light" metals such as aluminum, white metal or other alloys break down much quicker than steel, cast iron or brass. I think it's because at the molecular level, there is a weaker bond, but I am not a chemist. A smooth aluminum surface that has light surface corrosion can still be cleaned with electrolysis, but only immerse the material for short periods (15 minutes) and clean with a soft brush. Longer periods will discolour, badly pit or even completely dissolve aluminum etc.

Also, materials with a thin or not well bonded electroplated surface may be adversely affected by long periods. The plated surface may actually peel away. Experimentation is required no matter what you are working with. Try short immersions first and gradually lengthen the periods. My main tests on heavy, thick cast iron and brass parts show that they can be left "cooking" in the electrolysis bath for hours, days even weeks with no noticible loss of metal and the brass may have some tarnish or discolouration. This is cleanable with conventional metal polish and/or a buffing wheel.

Precious metals,(gold or silver) can be cleaned but;

a) Some amount of precious metal is removed and this may be highly undesirable.(I did try a dirty gold neck chain. It worked but likely devalued it).

b) If the item is plated (brass, gold, siver), it may peel off the plated layer and effectively ruin it.

c) Coins and other items with fine detail can be cleaned but the delicate lines and raised words may be lost on badly corroded coins. If a truly vintage coin, other methods should be tried first.

So in general, experimentation is required while taking notice of the cautions outlined above. So don't blame me if your aluminum carburetor/engine block dissolves overnight. Or if your silver-plated water jug is reduced to the original tin shell.

I can't emphesize enough that aluminum requires special care. The polished housing on a motorcycle engine can be pitted and etched leaving a very poor mottled surface.

Other information on what you can clean is in Questions and Answers.

Materials Required - In addition to the part you are trying to clean, you need:

» A non-electrically conductive container large enough to hold the parts you want to clean, (i.e. a plastic bucket ? or for large engine parts perhaps an old (fibreglass) bathtub ???). There are other containers like a 45 gallon (about 200 litre) plastic drum that are used for soap and other materials sold in bulk. They are sometimes available cheap or free at recycling centres. An entire single cylinder engine could be put in one of these.

You could use a stainless steel bucket, sink, pot etc. connected to the POSTIVE post as long as you are careful not to let the part being cleaned touch the side of the bucket (short circuit will occur).

» A 12 volt battery or other DC power source with high current capability. A battery (in conjunction with a charger)will always give superior results. A trickle ( 4 to 12 amps) battery charger can be used for small parts. A shop grade "booster" battery charger is quite effective for even large parts. 6 volt DC works as long as the current ability is high. Higher voltage DC sources will work of course BUT then it becomes a shock hazard. (see safety rules below).

» Electrodes to connect to the positive battery terminal. Iron or any metal can be used. Aluminum used as the positive electrode deteriorates quickly. Iron (and maybe brass) would last longer but requires more frequent cleaning. Stainless steel is superior, it will last longer and needs less cleaning. The electrode can be wire, bolts, fasteners, screening, sheet metal or thick plate.

» Water to mix with the electrolyte. Distilled water is not necessary but wouldn't hurt.

» The electrolyte (see above for more information). I used Arm and Hammer WASHING SODA -a common laundry detergent. Main advantages here are; easy on your skin, NOT corrosive to the part being cleaned if you happen to leave the part in the solution, no worse than typical soap if it gets in your eyes, AND it leaves a nice soapy smell in the room. Also, the soap effectively gets rid of the putrid smell of old gasoline and oil. (great for cleaning out old gas tanks). Other soaps and detergents work fairly well and I'll leave that for you to experiment with.

Other electrolytes I have tried . Take note of the cautions mentioned

Baking Soda - Sodium Bicarbonite. It works but has much the same properties as salt in that it is mildly corrosive once electricity is applied. I have used it only only for brief tests. It is probably better to use it in place of washing soda than the others which follow.

Table salt- it is corrosive to metal in it own right. It also leaves a punjent chlorine smell behind. (It is sodium chloride). Very bad for aluminum.

Vinegar & acetic acid- Is a mild acid and has been reported to work but the smell it makes is undesirable.

Trisodium Phosphate (TSD) - Found in cleaners for heavy-duty use such as household wall and exterior cleaners, driveway cleaner etc. It is more caustic than soap (harmful to the skin and eyes) so extra caution should be used. The warning on the container says"CAUTION: Contains Trisodium Phosphate. Wear rubber gloves and eye protection. Avoid eye contact or prolonged contact with skin. Wash thoroughly after handling. If eye contact occurs, flush with water for 15 minutes. Consult physician immediately."

These work but are NOT RECOMENDED:

LYE - Sodium Hydroxide - Corrosive to metal in it's own right. Causes much more gasification of the water (LOTS of hydrogen and oxygen gas). Very hard on your skin and even worse CAN CAUSE BLINDNESS if splashed in your eyes. Very bad for aluminum , white metals (zinc alloys) or thinly electroplated materials.

Battery acid (sulphuric, hydrochloric, nitric) - I don't need to spell out that one for you do I? Way too hazardous.

Safety

(PLEASE read it all, especially the cautions regarding safety. Review the previous information on the type of metals you can work with and the suggestions on the "electrolyte" to use.

THINK SAFETY!!! - There are numerous common sense safety rules.

Power and voltage - Although you are working with a low voltage 12 volt system, some people may be more sensitive to that voltage. An unpleasant tingle will be felt if you touch both connectors from the battery or charger with your bare hands. More important is the high current capability. If you were to short circuit, the leads from the battery or charger, sparks will be created that could be a fire hazard. If you were to short circuit the leads with a coat hanger wire, a ring or necklace, it will glow bright red and cause burns and/or fire. To reduce the chance of personal injury, make all connections to the electrolysis bath before turning on the power. A shock hazard is more likely if you were to use a power supply greater than 12 volts.

Electrolyte - You may be using washing soda or other soap. They will not likely hurt your skin but splashing the soapy solution (which contains metal bits, grease and rust) in your eyes can't be good. If you use other electrolytes mentioned, they may be harmful to the skin and damaging to the eyes. Exercise caution

Gases produced - The electrolysis process splits water into it's elements, namely hydrogen and oxygen. Sparks (from the battery and connections) can ignite the hydrogen/oxygen mix. It is not enough to produce a Hindenburg-like explosion in your workshop, but it is flammable all the same so this should be done in a reasonably ventilated area and caution is advised.

Heat produced - Once the item to be cleaned has been in the bath for awhile, the water will get quite warm from the current transfer and may even be too hot to touch. This is a good way to help take apart seized parts without the use of torches.

Setup & Procedure

The example here uses a 5 gallon (20 litre) bucket. Use about 3/4 cup of washing soda in a 5 gallon bucket of water and mix thoroughly. If you are using larger containers, you will only need to add enough washing soda (or alternative electrolyte) to allow current to flow through the water. If you use other electrolytes, continue to add the substance until current flows (bubbling occurs). Excessive electrolyte simply uses more current without substantially improving the speed of the de-corroding process. Slower is better. After all, your old "whatzit" has been in the woods or under the ocean for decades or centuries,... what's a few more days?

Place the iron or stainless steel electrode (rods, plates,wire etc) in the bucket and connect the POSITIVE battery cable. There must be a good electrical connection. Clean off any rust or dirt that may impede current flow. It might be best to clamp the electrode to the side of the bucket to keep it in place.

Connect the NEGATIVE battery cable to the part to be cleaned and place in the bucket. . There must be a good electrical connection. Clean off any rust or dirt that may impede current flow. The part could be clamped to the side of the bucket or alternatively suspended from the ceiling or from a piece of wood across the bucket. Turn on the power. You will immediately see bubbles and froth coming from the electrode and the part.

You may have to leave the part in for anywhere from several hours to several days or longer depending on the extent of the rust and paint BUT USE GREAT CARE with aluminum or other light alloys . In any case, it is useful to occasionally check on the part and partially clean it as the rust and paint soften. This can be effectively done with a small hand-held wire brush or stiff bristle brush and steel wool.

Large flakes of rust can be easily scraped off, smaller pieces will brush off in time and molecular-sized fragments float off into the water and become part of the froth on top. Paint may actually soften and can be peeled off in sheets, several layers at a time. This process is also good at softening rust inside water jackets and other tight places that are often difficult to get to. In addition, electrolysis will, in time, soften the rust layer between the piston and cylinder wall making it easier to remove. The same process softens the rust between a seized bolt and its threaded hole or nut making it easier to remove without heat.

You can place several items in the bath at the same time but the more items (thus greater electrical surface area) there are, the more current flow is required. This also means that the stainless plate (if quite large) also increases the current flow. In addition, the proximity of the stainless plate (positive post ) and item to be cleaned (negative post) changes the current required. The closer they are, the more current required. (just make sure they are a little distance apart-otherwise a short circuit) When cleaning large parts, a fully charged, heavy-duty 12 volt battery will be dead in several hours . So either use a smaller electrode, increase the distance between the electrode and part or use a BIG battery and /or heavy-duty battery charger.

As mentioned above, the rate of electrolysis can be affected in numerous ways. To reduce the process, increase the distance between the electrode and the part being cleaned, reduce the concentration of the electrolyte or reduce the size of the electrode. In all case, this increases the resistance which decreases current flow and slows the electrolysis process.

You can use any DC power supply of any voltage. Avoid high voltage just because of the shock hazard. A battery charger will work, especially if used in conjunction with a battery. (The charger will help keep the battery "up" or if you use a shop type "booster" charger, it can be used by itself. A 4 amp trickle charger won't do much except for small parts).

When you are finished cleaning the part, wash it with fresh water and dry it thouroughly over a heater or in the sun. The freshly cleaned metal will rust very quickly. It might be best to either prime the metal or spray with a light oil or penetrating oil (like WD40) to stop flash rust from occuring.

Also remember that ( with iron at least) if the part you have cleaned comes out looking badly pitted and rounded off, electrolysis did not do it. This is what the item looked like after natural corrosion ate into it.

Special Cleaning Methods

How to clean a bunch of small parts.

If you have a lot of small parts (like a bucket of bolts), you can use a stainless steel screen (a common kitchen strainer works) shaped into a pouch or mini-bucket. Place some of the parts in the screen and immerse in the electrolyte as if it were a single part. Connect the battery NEGATIVE to the screen. All the metal parts which touch the screen (and in turn, each other as the corrosion dissolves and the parts can electrically touch each other) are cleaned together. Use a brush to stir the parts around occasionally. This helps to remove loosened corrosion and improves the electrical contact between pieces. In time, all parts will be mostly de-corroded. Compare this to wire brushing 100 bolts individually.

Cleaning inside a tight area like a engine water jacket

Take a small diameter plastic or rubber hose, cut numerous small holes in it and slip a length of stainless steel wire through the length of the tube. Feed this assembly into the water jacket (or whatever you're working with) and connect the POSITIVE battery wire. The electrode is now inside a tight area and in close proximity to the part/area you want to clean without touching it. Getting all the loosened crud out can be a challenge but vacuuming, compressed air or turning the unit upside down to dump it out works. One problem is that the process causes large chunks of rust to drop off inside the unit. You may need to reach inside with a screwdriver or rod to break up the rust to get it out.

For cleaning inside of cylinders or other parts, use a stainless bolt or wire supported and hanging freely within the part. This will clean inside areas that can't be normally reached such as a gas tank .

Cleaning large items

The use of a drum (45 gallon) was mentioned above. These are usually big enough to place an entire small engine in (or lathe bed or wood stove etc). Surround the inside of the drum with screen or sheet steel (stainless is better) and connect to the POSITIVE battery lead. Lower the entire engine or part into the centre of the drum using an engine hoist, chain block or suspended from the ceiling. Connect the NEGATIVE lead. Over time and with some brushing, the whole unit will be free of rust, grease and paint before you even take it apart. This will require considerable current so a large battery charger capable of maintaining 30 amps or more will be needed.

REUSE the electrolyte

After a while, the electrolyte gets quite dirty with suspended metal and dirt or grease. I have found (at least while using washing soda) that if you remove the electrodes, wires and parts from the electrolysis bath and leave the liquid to sit a few days, most material drops to the bottom. Siphon off the clear liquid at the top and re-use it, perhaps add a bit more electrolyte before starting the process again. HOWEVER, some material will remain in suspension and may affect (discolour) the part you are cleaning.

Example: If you have just cleaned a lot of brass, the electrolyte gets a green hue. Cleaning steel in this liquid may leave it with a slight brown discolouration. If this is undesirable, you will need a fresh batch of electrolyte.

If you don't intend to reuse the electrolyte and it was not used for extensive de-greasing, it can still be used as a soap to remove dirt and debris from metal.



THIS IS NOT A MIRACLE WORKER. Some good old-fashioned elbow grease will still be needed but the effort is much-reduced.

Questions and Answers

The instructions mention a preference for stainless steel electrodes. Why?

The electrode connected to the postitive battery contact gains material during the process of removing it from the part you are cleaning. Aluminum and steel hold on to a lot of this material, (rust, corrosion, iron or copper bits) and eventually create an electrical barrier which nearly stops the current flow through the electrolyte. Regular cleaning of this material is needed by scraper or wire brush. Stainless steel does not allow as much material to stick, so it requires less cleaning and attention. In addition, stainless material does not break down fast so will outlast steel many times over.

Where to I get stainless steel?

Stainless steel is available in many forms. Wire, screen, bolts and thin or thick plating. These are mostly available at hardware stores or a bolt and fastener specialty shop. Stainless screen or plate may be available through a metal working shop that builds ducting or sheet metal products. New stainless is expensive but will last years. Try a scrap metal yard for pieces of stainless. You may even find pieces of automotive trim in an auto junk yard made of stainless.It was used as door moldings and window trim.

Can I remove the chrome plating from an antique weapon (a pistol)?

Probably not. The electroplating process, if done properly, will include an acid dip to remove all dirt, rust and oxidation. The item is then plated many times over. If the chrome (or brass or silver plating) is well-adhered to the base metal, electrolysis will not have any effect on it.

Can this be used to clean an all-aluminum motorcycle or other small engine?

If caution is used, it will help to remove layers of corrosion from aluminum. But if you are trying to free up a steel part within an aluminum casting, be warned, the aluminum will be eaten away much faster than steel. This could effectively ruin the machine. If you have no other choice, it may be worth a try.

Will brass and/or babbit be eroded using this process?

Any solid brass or copper will not be adversely affected outside of some discolouration. The babbit (lead alloy) bearings found in many old machines will deteriorate somewhat faster than steel but the surface will not be quickly etched. The biggest issue is how well the babbit was adhered to the base metal (iron or brass). If the bond is poor, the babbit shell will be undermined and eventually come loose. If that is the case, you should be thinking of repouring the babbit anyway.

Does the part need to be degreased before the electrolysis process? Will electrolysis remove good paint on clean, non-rusted metal?

The part you are cleaning needs no special preparation outside of insuring a good electrical connection. Grease falls off the part and dissolves in the soapy solution in conjunction with the heat produced by electrolysis. Paint, even baked enamel, will eventually peel off the base metal in single sheets.

How can I adjust the rate of the cleaning process?

Opposed to buying a very expensive scientific grade power supply to adjust the current flow, it is simpler to either a) use less washing soda to make a weaker electrolyte or b) move the part being cleaned away from the electrode. In either case, the resistance increases, the current flow drops and the process is reduced in effectiveness.

Can a small battery trickle charger be used?

Small battery chargers in the range of 4 to 10 amps may not be suitable. This is not because the current is insufficient but the quality of the direct current (D.C) is not good. Ideally, you want a pure DC source as that from a battery. Battery and trickle chargers must convert the 120/220 volt 50/60 Hz alternating current (A.C.) from your wall socket to 12 volts D.C.. The diodes (or rectifiers) which filter A.C. to D.C. are not very good in small and cheap chargers. The end result is the A.C. which gets through can cause as much material from the electrode to stick to the part being cleaned as what has been removed from it. Experimentation is essential in any case.

Have you cleaned springs using this method? I am wondering if there would be any loss of tension by running the current thorough it.

Yes I have cleaned springs and they should not be affected by electrolysis. A spring would normally only lose its tension through excessive heat or stress and electrolysis does not get that hot.I expect that if the spring is quite rusty, it will already be weakened in the pitted areas where corrosion is present .



User Feedback

The uses for this is quite broad with reports of successful use on stoves, lathes, engines and other car parts, tractors, WWI ordanance found on the seafloor and even Napoleonic -era artifacts. Here a couple of emails

.....I am using the electrolysis cleaning method outlined on your website to clean a 13" South Bend lathe. I am completely impressed by the results I am getting. I typically leave the parts in the tank for 24 hours. The grease disappears, the paint comes off in sheets, and the rust is completely gone. Nothing left but bare metal! Thanks so much for creating the website you did. I have found the instructions very clear. Just didn't expect the method to work so well! Thanks again for your work! Ron C. USA ...

......I collect old cast iron frying pans and electrolysis gets them clean easily and leaves a nice finish. Beats the heck out of my old method of scraping, and the lye treatment that was suggested by someone. Bob S, USA ....

......I tried it last night using a trickle charger (8amps I think), seawater, steel bolt as anode (+) and connecting the negative terminal to the aluminum part. It is scary how well that works. I just did some less critical parts like handles and levers. About 15 min. loosened all the paint enough to make it a 30 sec. wire brush job. A careful inspection with the magnifying glass did show some slight pitting. I would hesitate to do this with aluminum parts that have precise tolerance surfaces like blocks or cylinder heads. Still I am extremely impressed. Even if I can't use this one on every part it will still save me tons of time... Henry, USA

Your feedback is desired. Tell me of your success stories or alternatively, problems you encounter.

For clarification or more detail of this process contact me at: oldiron@antique-engine.ns.ca

The Nova Scotia Antique Engine and Tractor Association
--
Brett Sutherland & the 1.5 million mile 122 CANADIAN www.ecvintagevolvo.com