Electrolysis rust removal

Charles in Aus.

Well-known Member
A curly one and a problem that has me stumped .
The bucket of my loader is rusty inside , to clean this I filled it with water after blocking up the pin holes with corks and set up a standard electrolysis circuit .
Negative of the battery charger to the bucket , positive to a scrap of steel plate suspended from pieces of timber , no contact between the two .
Ordinarily when this is set up in a plastic tub it works well , 5 amps has the object to be cleaned fizzing away in a few minutes and clean as a whistle in two days .

Here is the problem , despite having everything connected the right way and polarity correct the scrap plate is fizzing [ being cleaned ] and the bucket is getting rustier !!

Only difference from normal is I am using the bucket as its own bath , I am losing sleep over this one .
 
The essentials of electrolysis are an electrolyte and two conductive electrodes in contact with the electrolyte and connected to DC. It should work independently of the physical shape of the container holding the electrolyte.
I always remember "red goes dead", meaning the positive (red lead) electrode will be eaten away.
So, given that your process seems reversed, I can only guess that your polarity is wrong. Could you check the polarity of your bucket versus the sacrificial steel plate with a volt meter?

Do not know your set up, but there could be secondary circuits. Is your loader bucket electrically isolated from everything surrounding it, including the floor?

HTH, Hendrik
 
Your piece of metal being used as the electrode
has to be large other wise there won't be enough
current. I'm talking the surface area to surface
area between your bucket and electrode should
almost be the same square inches.
 
F-I-T posted exactly how to do this. As I remember, there has to be some washing soda in the water for the process to work well. Maybe search the website?
 
In normal plating the workpiece is cathodic [ negative] and the current flows from the anode to the workpiece. So to strip chrome or rust the workpiece [ loader bucket] should be Anode positive and the cathode negative. The problem is every few square inches of surface takes several amps to get anywhere. And all this done at very low voltage. It is sorta like you are trying to electroplate a car with the current for electroplating a toothpick. If you added some sulphuric acid to the bath it would help alot.
 
I've used a piece of rebar stuck inside a gas tank filled with electrolyte to clean the tank--worked great. You seem to have it all right. Check the charger and make sure black is negative.

I'm almost positive I've seen the sacrificial (red) electrode fizzing at times and perhaps the fizzing is most apparent on the smaller of the (work vs sacrificial) pieces because that piece has more current per square inch of surface area going through it--I'm guessing here. I sincerely doubt that if you have black to the bucket and black is negative that the bucket is being eaten away regardless of what's fizzing.

That said, when I got my loader it had bad rust. I cleaned it with a $20 Harbor Freight needle scaler. Noisy but very effective and quick leaving only light rust. Short of painting inside--and paint is going to wear off in use--you're going to have rust--it's inevitable. I knock large clumps of dirt,or whatever out of mine after use and well, mine stays under cover so it's not rained in.
 
I won't use the anode method on many parts due to "hydrogen embrittlement" causing fasteners and important structural parts to become brittle and snap off. . Look it up. Sometimes you are better off blasting.
 
Thanks for all the replies .
The polarity is correct , and the electrolyte is the same as I have used for the boom and other brackets , caustic soda [ lye] and washing soda in plain tank water .

The supply I am using provides about 5 to 7 amps at around 15 to 20 volts DC and has literally torn the rust off everything else so far .
Hendrik the bucket is not isolated , I did wonder at the time , now with 300 odd litres in it I will have to drain it to try again . This really is the only thing that makes any sense at least at the moment . John B , the sacrificial plate is about two square feet in area , nowhere near the surface area of the interior of the bucket but it did work in a bath twelve feet long I made for the boom . There were three of them for that bath though .
I have taken some photos , and will post them later today , still really perplexed over this one , but at least now I have some solutions to try . Thank you everyone .
 
I'm no expert, but I'm wondering if you've got
enough "juice" for such a large job.

That's a whole lot of surface area - thinking
you might need something a little more powerful
to get it done, and all your doing is letting
everything rust.

Do you have an ammeter to see how much current
you're drawing?

Surface area definitely matters with
electrolysis - I just can't tell you how MUCH
it matters. I'm sure there's a formula out
there for voltage/current based on sq/ft or
inches.

I'd start by googling it.
 
Rust on the inside of loader bucket? Just load some sand or gravel , should clean it up. joe
 
I am really grateful for the combined thought given to solving this problem , nice to know you are not alone with difficulties even if they are minor ones .

The amperage I have been using is the same as I used for the entire loader boom , the bath was over eight foot long and two feet deep , it did take seven or eight days to clean it but it worked very well . Not once did I have the boom fizz . I re checked the polarity and all connections . I even reversed the polarity , the sacrificial plate still fizzed !

So I then connected a piece of pipe from a drum pump to the negative line , insulated it from the bucket and placed it in the bath . Instant fizz , the bath worked just as it should and two hours saw the pipe corrosion free .

Re fitted the negative line to the bucket , checked the positive connections to the scrap plate and turned it back on .
Blasted plate fizzed instantly , perfect electrolysis but backwards and no amount of reversing current will correct it.
I am now thinking that Old 9 might have the only solution , either this or I am going to ask my Priest to perform an exorcism , it has got to be possessed with something to act this way
:?
 
Some photos , showing polarity and relative sizes , the plate is seen fizzing away so I can only assume that the bucket is receiving the rust . The amperage is at about 7 [ the scale is a little off ] ,voltage just under 20 DC.
Could the current be travelling to earth as Hendrick suggested ?
Last day of stuffing about with this one , if I can't solve it soon I will drain it and wire brush the whole thing .

mvphoto16266.jpg


mvphoto16267.jpg
 
Red to the sacrificial anode, black to the metal to be cleaned, strong basic solution. That is all you need. Do Not use an acid as the electrolyte! Both the part being cleaned and the sacrificial anode will form gases, hydrogen on one and oxygen on the other. The bubbles on your sacrificial electrode are normal, that is what you should see. You would normally see bubbles on the part being cleaned except your current is not near enough for the size of the part. Any gases at the part being cleaned are absorbed by the liquid before bubbles are formed. The surface area is way too large to form any bubbles for only 5-7 amps of current. That is why there are no obvious bubbles on the bucket.

The sacrificial electrode is being turned from steel into rust, that is what happens on the positive side of things. That rust will coat the tank and form an insulating layer. The bucket is not rusting more but you are just seeing the coating of rust from the anode which is disolving. Normally that coating will settle to the bottom not on your part being cleaned. In this case the tank bottom and the part being cleaned are the same thing. When I use the part to be cleaned as the tank as when I am cleaning a fuel tank, I do not use steel as the sacrificial anode otherwise you get exactly what you are seeing. I use carbon torch electrodes from a welding supply company. Any carbon that collects in the electrolyte will not insulate the tank being cleaned.

You have several choices, increase the size of the sacrificial electrode to increase the bubbles being formed on the bucket until you can actually see the bubbles. Those bubbles will stir the electrolysis solution enough to keep the rust from the anode from coating the bucket surface. Bubbles need to come from the surface being cleaned, they are part of the cleaning process since they help mechanically loosen the surface rust. The more bubbles the better. A larger anode, more washing soda, and higher voltage will all increase the current. For a bucket, 20 amps or so would be good.

The other option is a wire brush or sandblaster. Faster.
 
Many thanks electro , a very lucid and logical explanation . Especially concerning the oxygen bubbles generated on the anode . I have since increased the size of the anode considerably and found it to work as normal . Yes the amperage is low , I generally just leave it in the bath for a longer time .
mvphoto16318.jpg


Shown here is a lid from a 44 gallon drum , the bucket is a scant 4 feet wide and 2 deep , seems to be working well now . Shortly after taking the photo bubbles were leaving the bucket surface and rust is collecting heavily on the drum lid .

Thanks to everyone :D
 

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