Electrolysis

Are there any limits as to how long you can run this process- can it damage good iron/steel like remove carbon if done too long. Have parts mostly clear of rust and parts continue to bubble and I wonder what is happening. Any insight appreciated. Thanks, Charlie

There is only one time when I suspected noticeable damage to a part undergoing electrolysis for an extended period. It was a machined cast-iron surface.

That said, I once fell heir to a post drill that had been in a fire. I put it into the electrolysis vat and then went on a three week trip. When I got back all the stuck parts had been freed up and the rust was gone. I didn't notice any damage from prolonged treatment.

But... there are very few machined cast iron surfaces on a post drill.

Generally speaking, badly cast iron will clean up in a day, or so, making prolonged treatment un-necessary. Sometimes, rough castings have an unsightly surface skin. This was caused at the foundry and no amount of electrolysis will accomplish anything.

In my experience, badly pitted steel can take a long time to clean up. I've never seen any visible damage to steel from long-term electrolytic de-rusting. On the other hand, this is no sign something bad isn't happening on the microscopic level. If it's a critical part, either buy or fabricate new. Then, you won't have to worry about it.

My electrolysis operation goes 24-7, year in and year out. It beats abrasive blasting; and, when abrasive blasting is needed, electrolytic pre-treatment cuts cleanup time enormously, to say nothing about keeping the grit clean, longer, and improving visibility in the blasting cabinet.

I mean to say that badly rusted cast iron will clean up...

I'm curious- what do you use for a power supply?

I use 6-12 volt battery chargers. If the current draw is too high on 12-volts I can switch it down to 6.

Sometimes, I'll use two battery chargers at once on two different items in the vat. In those cases I use two waste (+) electrodes.

When I don't use two chargers, I connect the two waste electrodes together, electrically, so the part being de-rusted will almost be surrounded. Using this technique, I don't see any "line of sight" action. The entire surface of the part is de-rusted without having to turn it.

It sounds like you have got things worked out real well.

I, too, use battery chargers mostly, but I am using small ones in the 8 amp range and am not seeing any high amperages. I have a 5 gallon plastic bucket with 4 pieces of re-bar as electrodes.

Frankly, I would like to see a little more action from my set-up than I am getting, though overall, it is quite effective.

I experimented with much larger voltages and amperages and got some badly stuck larger pieces apart, but got dizzy watching the meter on my electricity bill twirlin' around. Also, I felt I had to babysit the thing because I'm in the big city and even though it was in the back yard......well, you know! Plus, it could overheat!!

As far as leaving something in the "vat" too long and being damaged, I cannot answer for sure but I have observed a few things. If the process stops for one reason or another and the pieces are not removed and dried, I'm pretty sure they will rust. This could occur from a blown fuse or a wire knocked off or something simple. And,I'm not sure if the power input suppresses rusting if the sacrificial electrodes become overloaded with crud.

If a part I am cleaning has any machined surfaces like a bore or a journal, personally, I never allow much elapsed time between checks and as soon as the rust is gone,I remove the parts and dry them, oil the machined surfaces and put 'em in an oven at 250 degrees F until all the moisture is surely gone.

I haven't damaged a piece with electrolysis yet, but I can't make that claim with regard to hammering, torches, and presses. Dang it !!

I'm gonna keep on playing with the small set-up. Electrolysis really is something that I consider bit of a wonder and I learned all about it from you guys on Harry's site. Thanks, fellas !!jw

There are a number of things that will affect the current draw; but, if either the part being cleaned or the waste electrode is small, it's difficult to get much amperage.

A number of folks have used re-bar for the waste electrode, but let's face it. The surface area of a rod isn't all that great. I prefer to use large pieces of sheet metal or dented hubcaps.

This afternoon I put a six inch cast iron wheel in the vat. Mind you, there isn't much to it: six slender spokes, a small hub, and a 1-1/2" wide face (tire). It pulled about eight amperes. The waste electrode was about 12" X 12".

I wanted to reduce the current because I didn't want any connections to overheat. There are two convenient ways to do it. Increase the spacing between the waste electrode and the part being cleaned; or, reduce the voltage. I elected to reduce the voltage because that would reduce the power consumption.

Thaks for all your input! While I got your attention, does electrolysis affect diecast, aluminum, or brass parts- or do these parts have to be removed first? Whats your experience, I've been afraid to try.

Just a few basic things I've learned; Maximum electrolosys operation is acheived when the sacrificial anode is equal in area to the piece being derusted. Chances of overheating are minimal when a sufficient volume of electrolite is used (water discipates heat). This process is a great place to use those old battery chargers that are no longer effective for charging batterys. Connections (electrical) to both the anode and workpiece are very important. Electrolosys is the cheapest method of rust removal around. Electrolosys does not damage aluminum, bronz or babbit. Even if the process isn't working, chances of rerusting of a part immersed in the electrolyte are minimal. Allowing the workpiece to form a thin coat of rust post derusting allows phosphoric acid to form an iron phosphate coating. Iron Phosphate is excellent as both a primer coat for painting, and is an impervious layer to rust.

While I haven't tried electrolysis on old machinery parts. I have used it to clean antique tools. I learned this through the Early American Industry association. I always used Stainless to attract the old rust which allows the rust to fall to the bottom of the container. I'm new to this link and have not followed all the previous discussion. Dick in New York

I've been using stainless, too, for the past couple of years; but, it creates its own hassle. I like the way the electrolyte stays relatively free of rust, but after prolonged usage the electrolyte takes on a wicked yellowish tint. One will also note that their stainless electrode is gradually disappearing.

This is not good. Stainless steel contains a considerable amount of chromium. The yellow color of the water screams "chromate." Hexavalent chromium is poison.

Don't dump your chromate-containing electrolysis water on the ground. Don't flush it down the drain! If you get chromate in your drinking water well, you're sunk!

I took great pains to carefully dispose of last year's electrolysis water. I put it into buckets and let it evaporate, completely. (We can do that in this arid climate; the water evaporates quickly and the bucket isn't refilled with rain water.) After it was completely dried I had several pounds of dry material that I disposed of as a hazardous waste.

You can avoid all the hassle by using graphite "waste" electrodes. Graphite is ordinary carbon and won't create any poisonous byproducts. I got lucky and acquired about 700 pounds of the stuff. The next time I mix up a batch of fresh solution I'll be using graphite electrodes.

Being naturally cheap, I've always used junked lawnmower blades for anodes. From what I've read on the scientific type boards, where the process is being used on recovered saltwater wrecks, the favored anode seems to be stainless. The biggest factor with anodes is that the area of the anode should match or excede the area being derusted. Essentially, this is just an electroplating process where the rust is being plated onto the anode.

How long does this take to work? couple days?

Scott

You will find this answer frustrating, but...

It all depends on the base metal and the nature of the rust. In my experience, electrolysis can act very fast on cast iron that doesn't have any "stubborn" rust. If the cast has gotten rusty from just sitting out in the weather for a long time, I've found that electrolysis can "lift" the rust off in about four hours. It will still be clinging to the part, but a quick wire brushing under a stream of water will make a miraculous transformation.

I'd say that on the average, I leave cast-iron in the vat for a day and then wire brush. If there's more rust, I'll throw it back in for one more day. After that, if there's still rust, it gets a quick abrasive blasting treatment. Electrolytic pre-treatment cuts the abrasive blasting time, enormously.

Then, there's the stubborn rust. Let's say it's a cast-iron wheel that's been partially buried in the dirt. Under these conditions there's a hard, crusty layer of rust that prevents the electrolytic solution from soaking down to the base metal. No amount of electrolysis will remove it... in a reasonable amount of time, at least.

I'll generally use a combination of electrolyis, acid treatment, and abrasive blasting on the stubborn stuff.

In my experience, pitted steel will often have the stubborn rust. If the steel is not pitted it will generally clean up in a day.

After electrolysis, if you don't follow up with chemical treatment, the part will turn rusty-red as soon as it dries off. Actually, there it takes very little rust to make a part look reddish brown. I use either Ospho or Metal Prep to remove the red rust and passivate the surface.

These phosphoric acid/salts treatments can be frustrating. If you put it on too thick, some brands of the stuff will form a sticky surface. If you try to thin it down with water, it dries to an ugly white coating.

I've found the trick is this: Put it on very sparingly. Brushing it on may put on too much. I generally brush it on and then immediately mop off as much as I can using a rag made of synthetic material. Cotton or paper towels will not work. The acid eventually causes them to deteriorate and leave bits and pieces embedded in the surface.

It might sound like a bit of a hassle, but the metal prep treatment is worth the effort. We live in a dry climate, so rust isn't a worry. Often, the treated part will take on a natural "just-out-of-the-foundry" appearance that is very pleasing. When this happens, I'll leave it as-is without painting.

The "ugly white coating" you referr to after phosphoric acid treatment is called Iron Phosphate. It is a desired effect, as it is both an impervious coating, and an excellent surface for paint to bond to. I generally use between 3 and 5 % phosphoric acid in water for acid treatment, and have even used an electrolytic process to gain speed on the acid process. Electrolosys will remove even the nastiest coat of rust, over sufficient time, and will remove rust abrasive blasting doesn't get to, especially in the microporoscity of castings and voids between parts. From my experience, the only time I'll blast something is if I need it NOW! Electrolosys is by far the preferred process, in terms of cost as well as damage to components.

I agree with everything you say. However, in those cases when I want to leave an item unpainted, I'd rather not have the white show up. I'm guessing that there is no difference, chemically, between the surface that looks white and the surface that my technique uses. Either way, if the item is painted, it won't make any difference.

I agree. I hardly ever use my bead blasting cabinet any more. I don't care for the raw surface that is left by abrasive blasting. And, if left untreated for a couple of days, the rust that was left behind will stick out like a sore thumb. Abrasive blasting leaves plenty of it behind.

[Harry]

I don't care for the raw surface that is left by abrasive blasting. And, if left untreated for a couple of days, the rust that was left behind will stick out like a sore thumb.

The phosphoric acid I use is available at Home Depot by the gallon jug. I pour about 1/2" into a coffee can and paint it on with a paintbrush, then wipe the excess with a paper towel. It leaves a dark finish and when dry, it's ready for paint or leave it as it is.

Harry, my experience with Phosphoric, about 50 gallons of 85% so far, is that when applied to iron or steel at 4%+/- concentration in water, the color of the iron phosphate coating is never known in advance of the complete reaction. White -v- black seems to be more a function of the composition of the iron or steel treated. Disolving magnesium in the solution will better the chances of developing a black coating. Boiling a part in Phosphoric acid magnesium solution will usually result in a finish close to Parkerising.

I believe that iron phosphate is black and the white powdery substance is unreacted, dried phosphoric acid. The white stuff should be washed off. Reading the directions on Ospho and similar, this is usually stated.

Another similar metal treatment chemical I use in ship repair is called "Conquest". The label says that a main ingredient is tannic acid. Treated bare metal takes on a purple hue. Like Ospho, it is a very low viscosity liquid- a little can go a long way, but it is kind of expensive.

I use it on steelwork and welding that won't get painted for a while, sometimes a couple of months. At home though, I use phosphoric acid because I can get it cheap,.

Here's the formula for the Tanic acid compound sold as "Rust Neutralizer"Rust Neutralizer 8% Tanic acid 4% Oxcalic acid 4% Ethalene Glycol 5% Ethanol 81% Water From what I've read, this formulation "converts" the rust into an impervious plasticized coating. The thing that doesn't get discussed in the literature is the depth of the coating. Other published information on tanic acid use varies from soaking the object in a container of strong tea, to some interesting papers on www.finishing.com where there are references to "electrobrushing". At this time, I have yet to experiment with any tanic acid process. I have obtained great satisfaction with paint applied over phosphated steel, some of witch is currently 20 years old, and exposed to the elements every day. The only post acid treatment I've ever done was light sanding, or skotchbrite, prior to paint application. I have found that the longer the acid remains liquid increases the depth of penetration. I've also soaked some items, as well as appiled a DC charge to submerged items in an acid tank with good results.