electrolytic rust removal

[MattF]

(Dammit, I wrote a whole thread about this restoration but didn't think this forum would be so interested!)

Not everyone on here are welders you know. Can't have too many old machinery/equipment restoration threads.

 

[Maker]

This is my new setup, there's 4 bits of rebar and a piece of 3" flat bar in the bottom, I'm using it to clean bits of my grinder.

It draws around 2 amps and doesn't bubble nearly as much as my previous setups. I'm using the Bremi 3 amp supply from last time.

 

[DAPPH]

Nice picture Maker, as I have one of those smaller yellow muck tubs may I ask how much washing soda you used in your electrolyte ?
Is there any special reason as to why your electrodes are such long lengths ?

As an aside note of interest or not ..
I learnt a few days ago that quality pure uncontaminated distilled water does not conduct electricity .... even it it is in the order of a lightening strike ... Anyone fancy trying to disprove it , please gift all of your gear over to me in the first instance before you start your experiments .. i solemnly promise I''ll look after it well ......if things go wrong .....

 

[ronan]

Didn't everyone know that pure water is an insulator and it's only contaminants that conduct electricity?

Yeah, i've heard so many people saying that water is an excellent conductor of electricity. They are often shocked when i tell them it isn't.

 

[Stuart Garland]

I've just joined the forum and stumbled across this thread. I have used cheap white vinegar to remove rust from steel/iron. Soak it over night. It's as clean as a whistle next day. Bigger itemds i have put in garbage bags, expelled the air and tied it off. It's cheap and works.

 

[droopsnoot]

I've tried various methos, including vinegar, various acids, and electrolytic. I'm told molasses is very effective on the inside of fuel tanks, though I haven't tried it myself yet. I'm having trouble with my electrolytic cleaning at the moment, but it has worked very well for me in the past.

 

[Screwdriver]

Yeah, i've heard so many people saying that water is an excellent conductor of electricity. They are often shocked when i tell them it isn't.

err, don't you mean not shocked??

...I'll get me coat.

 

[bigegg]

I cant show pics atm, cos i'm moving house.
But: my E.R.R. setup is a cast iron (?)
truck brake drum in a large plastic "trug" (? - flexible plastic circular tub used for mixing batches of plaster-a bigger version of the yellow tub^^^).
I lined it with 2in thick open foam rubber "sponge" to prevent short circuits.
Power supply is a farnell 3a 1-30v regulated.

 

[Screwdriver]

Electrolysis requires line of sight between sacrificial anode and cathode. Foam will interfere with the process. Much better to suspend items so they don't touch the anode.

S.

 

[bigegg]

Electrolysis requires line of sight between sacrificial anode and cathode. Foam will interfere with the process. Much better to suspend items so they don't touch the anode.

S.

Not my experience.
The foam i use is VERY open, however.

 

[Screwdriver]

Foam will interfere with the process, not having line of sight will slow things down. Best bet is to have the anode surrounding the item to be electrolysed with nothing in between except the electrolysing solution. I have discovered this by trial and error but if you have the time, virtually any old setup will work eventually.

S.

 

[DAPPH]

I'm hoping to use five or six thickness of hard plastic 1/4 " mesh netting for e separators & mats as it is all holes .
Tthe bits that connect the all holes together is 1.0 mm thick & heat fused at the cross over points..
It's as tough as old boots for its rigid black Kevlar nylon .
Happily I've been given a 1960's , 6/12volt battery charger , I have a big plastic tub , plenty of rain water & some washing soda .
All I need now is something to de rust

 

[Screwdriver]

Sounds like you are going out of your way to block the process before you even start. Length of wood on top, hang the item in the solution. Use the mesh to hang it if you like but it will end up with a printed pattern!

Since I have only been blasting relatively crude and badly rusted items, I haven't bothered with the subtleties of the process. The idea is to fix the underlying oxide layer by converting it back to iron. Too many amps and the new surface layer will be a dusty coating rather than a solid reconstruction but if there's no detail on the piece, I wouldn't worry about it and the process will complete within a day.

The "line of sight" between the anode and cathode is the typical path the current will take and if there is something in the way, a stronger current will blow the surface off one area while reconstructing the other. Probably worth considering if its a machined flat surface where the slight patterning might show. Most of my stuff gets hit with an aggressive wire wheel afterwards (vices, heavy machine castings etc) but more delicate parts with for example engraved or etched lettering would benefit from lower current over a longer time.

S.

 

[MattF]

Since I have only been blasting relatively crude and badly rusted items, I haven't bothered with the subtleties of the process. The idea is to fix the underlying oxide layer by converting it back to iron. Too many amps and the new surface layer will be a dusty coating rather than a solid reconstruction but if there's no detail on the piece, I wouldn't worry about it and the process will complete within a day.

There's no reconversion back to iron. Oxide will remain exactly that. It may change state somewhat, but it will still be oxide. Unless you're plating, what's gone is gone and nothing gets added.

The "line of sight" between the anode and cathode is the typical path the current will take and if there is something in the way, a stronger current will blow the surface off one area while reconstructing the other. Probably worth considering if its a machined flat surface where the slight patterning might show. Most of my stuff gets hit with an aggressive wire wheel afterwards (vices, heavy machine castings etc) but more delicate parts with for example engraved or etched lettering would benefit from lower current over a longer time.

The line of sight thing is a misnomer. It doesn't matter whether there's line of sight or not. If electrolyte is touching all of the piece, the whole surface will conduct. It's simply that any electron flow will always take the easiest path, but in an electrolysis setup there is no direct path, so the piece will derust overall regardless. It may merely take longer for certain portions to derust, but derust they will.

 

[Henrik]

There's no reconversion back to iron. Oxide will remain exactly that. It may change state somewhat, but it will still be oxide. Unless you're plating, what's gone is gone and nothing gets added.

The oxide (aka rust) gets reduced back to pure iron. However, if the part is badly rusted, as iron expands when it rusts, the rust will have pushed the iron away from the parent metal and it may flake off.

 

[Screwdriver]

There's no reconversion back to iron. Oxide will remain exactly that. It may change state somewhat, but it will still be oxide. Unless you're plating, what's gone is gone and nothing gets added.

Err, but there is! The underlying iron oxide otherwise known as magnetite will revert to iron and if it does that gradually, that new layer will be shiny and new under the black magnetite which will rub off. You are effectively electroplating the surface with material from the steel anode.

The line of sight thing is a misnomer. It doesn't matter whether there's line of sight or not. If electrolyte is touching all of the piece, the whole surface will conduct. It's simply that any electron flow will always take the easiest path, but in an electrolysis setup there is no direct path, so the piece will derust overall regardless. It may merely take longer for certain portions to derust, but derust they will.

It is a misnomer but it does work in practice. Parts which have a line of sight to the anode are cleaned much more quickly and efficiently than parts which are not. This is especially true at higher currents and I expect a lower difference at low current/long duration treatments.

I am going to experiment with a lab power supply and test this theory next time I have a job to do.

S.

 

[MattF]

Err, but there is! The underlying iron oxide otherwise known as magnetite will revert to iron and if it does that gradually, that new layer will be shiny and new under the black magnetite which will rub off. You are effectively electroplating the surface with material from the steel anode.

We'll just have to agree to disagree on that point.

 

[Screwdriver]

Underneath the crust of red ferric oxide is a layer of black rust, aka. Magnetite. It is chemically an oxide of iron with the formula Fe3O4. This layer of black oxide is reduced in the electrolytic process, back to regular iron while the red rusty flakes are of course removed.

 

[Kram]

Used a small pc power supply to do lathe dial. Its a small item so used a spray can cap as the container. Had an outer bearing race perfect size, used that as anode, with dial sitting ontop/inside. Markings are stamped rather than etched, so no damage. Used some old rag as a spacer... Pb batterys use fiberglass between the plates, anything thin and porus will do. Added quite a bit of salt. On 12v it wanted 20 amps. 5v was quite a bit less, but still only needed half hour.

 

[DAPPH]

Used a small pc power supply to do lathe dial. Its a small item so used a spray can cap as the container. Had an outer bearing race perfect size, used that as anode, with dial sitting ontop/inside. Markings are stamped rather than etched, so no damage. Used some old rag as a spacer... Pb batterys use fiberglass between the plates, anything thin and porus will do. Added quite a bit of salt. On 12v it wanted 20 amps. 5v was quite a bit less, but still only needed half hour.

Piccies Please !

A picture or three will speak a thousand words or more .