Thread: Electrolysis using an old computer power supply

Originally Posted by Stustoys

"Carbon arc rods" are (not surprisingly) made from carbon, not sure what effect the copper coating would have. Ebay has some, no idea what there price is like compared to local prices but I can guess.
Stuart

The empty carbon arc rod packet I saw at work says 80-90% carbon and 10-20% copper.

I'm not sure it matters in most cases if the iron gets some copper deposited on it anyway, it will just protect the iron.

If it is, just soaking them in aqua-regia for a day will dissolve out the copper, at least far enough into the rod to stop it fouling the electrolysis.

Originally Posted by nadroj

Thanks Bob.
That's interesting about using carbon rods. It is a nuisance having to clean or replace the electrodes. Where could one get some rods?

Jordan

would carbon rings work or even 1/3 carbon rings

Originally Posted by azzrock

would carbon rings work or even 1/3 carbon rings

how about brushes from large dc motors

It's probably worthwhile mentioning that the metal piece to be de-rusted should not be allowed to come in contact with the sacrificial rods. You don't want to let the smoke out of the power supply. In a bucket situation, a plastic pipe with lots of holes drilled through it and slid over the rod works well.

how goes it go with paint

Originally Posted by sjm

It's probably worthwhile mentioning that the metal piece to be de-rusted should not be allowed to come in contact with the sacrificial rods. You don't want to let the smoke out of the power supply.

Too late, I already did that (several times) but fortunately these power supplies are very well protected and they just drop out - not even a small spark. The 12V line is supposed to be good for 15A but it seems to cut out around 10A.

In a bucket situation, a plastic pipe with lots of holes drilled through it and slid over the rod works well.

Good idea - will work on that when I next clean up the tank.

I have had to suspend operations. Work is busier than a one armed wall paper hanger with fleas.

Originally Posted by azzrock

how goes it go with paint

The old vice has two paint layers - the original Dawn dark Red (baked enamel?) and another subsequently applied coating of black.

It seems to have stripped all of the black off within about 4 hours and 90% of the red after about 8 hours. Like I said above I've had to stop because I can't keep any sort of eye on it at the moment.

Originally Posted by BobL

Cheers ST

how long do you reckon something this big will take?

I found that it took a day or so to strip the rust and practically all the paint and filler from the castings of the bed of the lathe I am refurbishing. I also did the cast iron legs, and various other heavily corroded parts, and all the larger bits only took a day or two at most. I was though using the stainless steel tank as the anode, a practice which is frowned upon in some circles because of the potential to form toxic chrome compounds. I only used an Arlec charger 4 battery charger as the current source, and have no evidence other than the lack of visible coloured compounds being formed, that any chrome compounds were formed or not, and there was no sign of any fouling of the anode such as you have when using iron or steel for an anode. I have tried stripping the copper from carbon arc rods, and using them, but I could not get a clean strip using chemicals and techniques available to me at the time. If anyone has an idea for a source of graphite sheet or bar, I would love the details, as I am a great fan of electrolytic de-rusting. I will try to post some pictures of before and after shots, keep in mind that the harshest abrasives used were green scotch kitchen scourers, and grade 0000 steel wool, used by hand only. I have just tried to upload photos, but got an error message to the effect that it was interrupted due to a missing security token, and to report it to admin if unexpected, but when I tried to do that, it came back that I was making an invalid report. I have to head off now, and am not sure what the issue is here, cheers and best wishes to all,
Rob.

The carbon rods you are talking about do they just have a coating of copper on the outside? If so how about using the etching solution thats used to etch PCB boards?

Originally Posted by Ropetangler

I found that it took a day or so to strip the rust and practically all the paint and filler from the castings of the bed of the lathe I am refurbishing.

Thanks for the info. I guess it has been in a bath for a total of about 12 hours and it's almost done.

The power supply runs for about 2 hours before stopping and I'm not sure why. Sometimes I can just restart it and it runs again for an hour or so but other times it won't restart until I clear the scum off the top of the bath.

I've skimmed the scum off the top of the bath about 8 times and cleaned the anodes 4 times. I found just jiggling the anodes up and down seems to clear them

Originally Posted by Stustoys

"Carbon arc rods" are (not surprisingly) made from carbon, not sure what effect the copper coating would have. Ebay has some, no idea what there price is like compared to local prices but I can guess.
Stuart

i bought a pack the other day.$25 for a 1/4 inch pack at a welding shop in melb

you probably dont need to use as much washing soda... i read on the net that you only need a little and using more just makes it use more power and not go any faster. When I have done it like this it has seemed to work fine.

Originally Posted by gallegos

you probably dont need to use as much washing soda... i read on the net that you only need a little and using more just makes it use more power and not go any faster. When I have done it like this it has seemed to work fine.

That's what I've read as well.

I read one one site that recommended a handful of soda per gallon of water. Not a very scientific measure but I decide to measure this and it came out to about 10 g per litre and I ended up using closer to 5 g/L - this was also of the hydrated crystals rather than the dehydrated powder. It doesn't feel very soapy. Next time I make up the solution I am also going to use filtered water which will be purer (much less chlorine) that tap water.

Power draw is the product of voltage and current. I've read that using V's above 12V makes little difference and getting a good distribution of anodes around big objects is useful since it removes the rust more evenly. But adding more anodes increases the power draw increasing power consumption. Each of my anodes pulls 0.75 - 1A so all up about 4A. So far I'm happy with the output.

I finally got both pieces of the vice finished.

Just a reminder of what I started with.


And here's where I got it to.

Of course it can't make up for starting defects like what looks like an angle grinder swipe or two to the piece on the right.

Close up

That looks like another angle grinder rub on the side.

I'm reasonably happy with the removal of the rust. I was hoping to get more of the paint off but I'm not that fussed as this vice is going to get welding spatter and sparks all over it anyway.

And just for fun here is my next challenge, a 10 kg railway line mounting plate that has spent 6 weeks under sea water.