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Author: Subject: Electrolysis. See the light!
locoboy

posted on 18/12/03 at 01:13 PM Reply With Quote
an agitater wouldnt do anything if it only works in line of sight, a better solution is a spit to put the workpiece on or a rotating anode, to ensure 360 degree attack





ATB
Locoboy

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David Jenkins

posted on 18/12/03 at 01:19 PM Reply With Quote
I wonder if this process will remove mill scale from 'black' steel?

I've successfully used vinegar with some salt dissolved in it (mmm - tasty!) to remove rust and scale from smaller items, but it's smelly and the fumes tend to corrode any nearby steel items, which isn't so good.

The need to deal with the bare metal as soon as it's lifted from the solution is true in either method - the steel is ready to rust from the word go!

David





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JoelP

posted on 18/12/03 at 01:51 PM Reply With Quote
i suspect its not 100% line of sight, not sure how it works but im guessing that something in the soda allows electrons to move thru the solution, and the charge on the workpiece attracts them. as such they (the electrons) are unlikely to float past a bit of the target without sticking to it, but may get round the sides a little. agitating it might help, dunno cos i cant be arsed trying it!

suppose it can only help to put a magnetic bean in the bottom...

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sgraber

posted on 18/12/03 at 03:10 PM Reply With Quote
That's AMAZING!@! Too bad that Arizona is so dry that rust doesn't form like that. Would someone send me something rusty>?

Honestly, too cool! There should be a place on the forum for "it's a keeper" threads like this one.

Graber





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Peteff

posted on 18/12/03 at 04:08 PM Reply With Quote
I'm looking for a bath big enough to get this Capri axle in, anybody got one lying about. The wife caught me carrying it upstairs and she's banned it from the bathroom. If you like these kind of things you should go and look at the
http://www.lindsaybks.com/ website or the gingery site, some of my favourites but I daren't try some of their ideas out.

yours, Pete.





yours, Pete

I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.

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James

posted on 19/12/03 at 12:00 PM Reply With Quote
Pete,

Could you make something along the lines of a coffin sized/shaped box lined with a tarpaulin to hold the solution?

Or even just a wooden/metal frame work?

Failing that, it can't be that hard to find an old bath in a nearby skip. Use it then put it back in the skip!

HTH,

James

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timf

posted on 19/12/03 at 12:53 PM Reply With Quote
james

haven't you got a slightly dammaged bath pete could use

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craig1410

posted on 19/12/03 at 01:19 PM Reply With Quote
Hi,
For smaller stuff why not use a Stainless Steel Sink with a rubber mat in the bottom to avoid a short circuit or perhaps a sort of "hammock" arrangement to keep the piece off the bottom. Surely that would give as close to complete coverage as is possible without a fully enclosed box.

I've not tried this yet but I have an old stainless sink in my garage and several rusty bits to try it on.

Where is the best place to buy the Sodium Carbonate? Will Chemist's keep in in large enough quantities?

Cheers,
Craig.

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sgraber

posted on 19/12/03 at 02:36 PM Reply With Quote
I have successfully used my kids old plastic baby pool for large parts washing. Don't tell the missus. Some of them can be bought real cheap. It's a round plastic one with reinforced edges.





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Spyderman

posted on 19/12/03 at 07:35 PM Reply With Quote
Agitating the solution would be an excellent way of improving it's effectiveness.
The line of sight idea is only partly true in that the electrons, like all things find the shortest route is a straight line.
Agittating helps also to remove the loosened crude from the surface.

Adding another anode on the opposite side of the solution bath would help with the cleaning process much more effectively than using a stainless steel sink.
No reason why you shouldn't use a SS sink if you have one, but not really worth the hassle of obtaining one if you don't.
The risks of shorts is far greater the more anode you have, plus there may be small areas of impurities in a sink that will erode away and hence leak.
Another dissadvantage is that the larger the area of anode, the larger the voltage needed. Your battery charger or old computer PSU may not be upto the job.

Terry
ex Electrophoretic paint technician.





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craig1410

posted on 19/12/03 at 09:12 PM Reply With Quote
Hi,
Power shouldn't be a problem for me as I have an 18V, 10Amp variable voltage, variable current power supply. It is an ex-educational type unit which I bought at one of those radio amateur fair's and is of very high quality. However, I take your point about the potential downsides of using a stainless sink.

I have a big plastic packing crate which is water tight and I'll probably use it to begin with as the sink is very handy as a sink funnily enough... I'll try and find a couple of stainless offcuts for anodes.

Any suggestions where I can most easily and cheaply get the Sodium Carbonate?
Cheers,
Craig.

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JoelP

posted on 20/12/03 at 12:18 AM Reply With Quote
http://www.chemsoc.org/pdf/LearnNet/rsc/SodiumCarb_sel.pdf

its a corker this one...

actually its bloody useless...

[Edited on 20/12/03 by JoelP]





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craig1410

posted on 20/12/03 at 01:52 PM Reply With Quote
Hi,
I've answered my own question...kind of!
It appears that you can create Sodium Carbonate by heating Sodium Bicarbonate.
See
http://chemmovies.unl.edu/chemistry/smallscale/SS043c.html
and
http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=005yRH

Just heat it at 250F for long enough that all the water vapour and CO2 has gone. Then you should have Sodium Carbonate. Just make sure that you start off with pure Sodium Bicarb and not Baking Powder which sometimes contains all sorts of other stuff.

I have a 200g jar of bicarb in the over just now and will let you know if it does the job and try to give you a more accurate figure for required heating time.

Cheers,
Craig.

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craig1410

posted on 20/12/03 at 11:18 PM Reply With Quote
Hi again,
Fantastic!!! It works!!

I successfully decomposed my 200g of Sodium Bicarb into about 140g of Sodium Carbonate and I have tested the process on the Sierra rear caliper mounting bracket which was very rusty. It took a few hours but the rust just flakes off in chunks leaving a nice black metal finish.

I would recommend that instead of heating the Bicarb in the oven, just heat it in a saucepan for 10 minutes at a fairly low heat. This worked just as well as heating in the oven on a baking tray for 1h15m at 150degC and was much quicker obviously. Just make sure that you keep stirring and shaking it while heating to get an even result. I'd recommend weighing the powder before and after heating and you should see a reduction to about 65% of the original weight if it has been successful.

I see what you guys mean about the state of the solution after de-rusting a part. I DOES look like someone shat in it after a very nasty stomach upset!!

Anyway, well done Liam for finding this gem. We are forever in your debt!

I'll post some before and after pics tomorrow. I have a Cortina front upright in the solution for the night and I hope it doesn't completely dissolve...

Cheers,
Craig.

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MikeR

posted on 21/12/03 at 02:17 AM Reply With Quote
Question....

Why doesn't the part being "derusted" get into a circular situation where it rusts then gets de-rusted so eating the part away?

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blueshift

posted on 21/12/03 at 03:44 AM Reply With Quote
quote:
Originally posted by MikeR
Question....

Why doesn't the part being "derusted" get into a circular situation where it rusts then gets de-rusted so eating the part away?


As I understand it, it won't rust because of the voltage applied across it, and the fact that rusting involves tiny amounts of electricity.

Also the de-rusting involved turns the rust back into iron, so if anything were to rust again it would be some of that.

mostly though, the electric field, unless a chemist cares to correct me.

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JoelP

posted on 21/12/03 at 01:19 PM Reply With Quote
yeah, basically rusting is an oxidative process, like burning. Oxidation is the loss of electrons, reduction is the gain. Since the work piece is attached to the -ve terminal, it is flooded with electrons.

not sure what reaction occurs, but basically the rust is reduced back to iron from iron oxide.

is the gas that forms oxygen or carbon dioxide? and what is rust specifically? is it FeO2 or FeOH?





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Peteff

posted on 21/12/03 at 04:14 PM Reply With Quote
I found some stuff in the cupboard. It's sodium carbonate decahydrate according to the ingredient label. It's for washing stuff not cooking like bicarb. I'm going to see what it does tomorow as it's cold and dark out there now and I can't be bothered to get togged up.

yours, Pete.





yours, Pete

I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.

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Spottty

posted on 21/12/03 at 05:57 PM Reply With Quote
Wow, this is really cool!

Being up in Canada everything is rusty! My Civic hubs had about 10 layers of rust on them.

Now all I need is a garage to set this up! I am thinking about one of those larger pvc pools that they use for landscaping. It would work well with those larger parts andd you could probly do alot of other parts together.

Great post! It shoudl be a sticky or something!





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craig1410

posted on 21/12/03 at 06:15 PM Reply With Quote
Hi,
Only thing I'd point out is that if you make up a very large quantity of the solution it might be more difficult to change the solution regularly and believe me you will want to change it before long as it gets in a real state!!

Also, try to get a nice big piece of stainless steel plate for the anode as I have been using mild steel and it also gets in a mess very quickly and this causes the electrical current to be reduced. I think that wrapping a piece of thin stainless plate around the outside of the vessel and then putting the piece to be restored in the middle would be best.

I did one of my Cortina uprights last night and it came out great. Even the old flaky paint lifted away easily leaving the clean blackened metal. If you then rub the black metal lightly with emery cloth it reveals shiny metal. You should do this to key the surface prior to painting anyway but my point is that it only needs to be rubbed very lightly. I'll post some before and after pics tomorrow night.

Cheers,
Craig.

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MikeR

posted on 21/12/03 at 09:04 PM Reply With Quote
You know, its times like this i'm glad i'm lazy!!! I've been putting off taking an old stainless sink to the tip for months ......

boy do i feel like a dog with two dangly bits now

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blueshift

posted on 21/12/03 at 10:31 PM Reply With Quote
quote:
Originally posted by craig1410
Only thing I'd point out is that if you make up a very large quantity of the solution it might be more difficult to change the solution regularly and believe me you will want to change it before long as it gets in a real state!!


We found that it looks like poo juice when you've finished de-rusting a part, but if you leave it the rust or whatever it is floating around in suspension settles to the bottom so you can see what you're doing setting up the next part. I don't think the amount of crap building up has any effect on the process.

Using a stainless electrode will probably mean less crap everywhere, we're using mild.

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Rorty

posted on 22/12/03 at 03:38 AM Reply With Quote
MikeR:
quote:

boy do i feel like a dog with two dangly bits now



Well I just hope any dogs you meet actually share your perversion.





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Mix

posted on 22/12/03 at 10:23 AM Reply With Quote
Pete

That'll be washing soda then

The rest

I have used a 'J' shaped glass tube and some clear plastic hose to syphon off the clear electrolyte after the 'poo' has settled. Both items obtainable from Boots home brew counter.

Just don't suck too hard on the tube

Mick

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locoboy

posted on 22/12/03 at 11:37 AM Reply With Quote
Anyone tried doing this with a non steel part that they want cleaning, ie ally or some alloy?

What would be the outcome?

P.S what is the recommended ratio for mixing the soda and water?





ATB
Locoboy

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