Rust cleaning by reverse electrolysis

[SnakeyJ]

Whilst doing a little on line research on rust removal, for cleaning up an old lathe, I came across a neat trick on one of the engineer forums - reverse electrolysis:

http://myweb.tiscali...spatch/rust.htm

http://www.instructa...oval-aka-Magic/

http://www.frets.com...ustremoval.html

 

The method involves dipping the affected item in to a water/sodium carbonate (washing soda) electrolyte solution, with a low voltage DC supply (car battery charger).    The item to be cleaned is attached to the negative terminal and becomes the cathode, while a steel anode is attached to the positive terminal.      There are stern warnings not to use stainless, which may form toxic hexavalent chromium compounds!    The process will release a little hydrogen at the anode, so some venting may be required.   Otherwise the process produces rusty brown water, which looks unpleasant but is otherwise safe.

 

This looked worth a go to, so I popped in to my local supermarket this morning and purchased a kilo of Washing Soda.    Using a cheap but fused car battery charger and an old plastic wash basin I set this with a heavilly rusted faceplate from my lathe.

 

 

The basin was not deep enough to dip this in one go, so this has had about two hours a side (seen here during the second dip)

 

 

I've just given this a quick wash off and a quick rub with a kitchen scrubber and then wiped it with an oily rag to prevent the rust coming back.

 

 

Probably could have done with a little longer and a better clean and polish, but a massive improvement.

 

I popped in to my local steel fabricators this afternoon to scrounge some scrap offcuts from their skip.   The guys there said they use this method all the time and showed me the old iron cylinder head they have been using as an anode for a the last 20 odd years!

 

Flushed with success, I'm just trying the wet towel method to try and shift some surface corrosion from the lathe bed.

 

 

 

I'll give this an hour and post an updated picture later.

[JamesF]

I've not heard of this before.  Seems to do a decent job.  I'm quite impressed.

James

[D4N]

They do something similar with ships, they use a stainless anode and run a current through the hull to stop it from rusting. The sea is the electrolyte in this case.

I've not seen it used on such a small scale before

Sent from my iPad using Tapatalk

[SnakeyJ]

Ok the results are in on the lathe bed and it works   Here are the results after just about an hours test.

Quite a bit of rust evident staining the towel:

As it is uncovered - black oxides evident:

After a quick wipe with a wet J cloth:

After a very light wipe with kitchen scrubbing pad, followed by oily rag:

Quite evident where the cathode and towel contact ended - wish I'd scrounged a longer bit of steel plate from the fabricators yard!   I'll do the other side tomorrow

[SnakeyJ]

Another example, a heavily rusted lathe back plate.    I dipped this last night and left it running overnight on the chargers low power setting:

 

The next three pics show it after it comes out of the dip, after a quick wash 'n scrub to remove the crud and finally after a spin and oil on the lathe.

  

I suspect the deep pits are imperfections from the original casting.

Pretty impressive results and not too messy.   I could easily and quickly achieve this with a wire brush and emery cloth, I think the main advantage is that this does not remove any sound metal.

Edit - some of the guides mentioned that the effect was directional and that anodes should be placed around the part being cleaned.    Judging from my own results I think this is rather over stated, though perhaps it might work more quickly.     I would suggest a big anode and sound electrical connections are probably more important.

[spaceboy]

Thanks for posting. My guess is as you have pointed out that the main advantage is that your not altering machined surfaces by pounding on it with wire wheels or emery cloth. I would be a little concerned of flash rusting so it may be worth considering all your options for corrosion resistance in the future. I have used an industrial strength degreaser in the past to clean bearings and you can almost guarantee if left they will be covered in rust by the morning no matter what lengths I go to, to dry them. Long term it's no so much an issue with bearings as grease is ever present. It's good dropping a film of oil over the surface of the treated parts but consistence in doing so every time the lathe is used may start to lapse in time ?

All said and done this looks a great solution to remove rust from those hard to reach places and sure does save some hard work on those fingers and thumbs.

[SnakeyJ]

Thanks for posting. My guess is as you have pointed out that the main advantage is that your not altering machined surfaces by pounding on it with wire wheels or emery cloth. I would be a little concerned of flash rusting so it may be worth considering all your options for corrosion resistance in the future. I have used an industrial strength degreaser in the past to clean bearings and you can almost guarantee if left they will be covered in rust by the morning no matter what lengths I go to, to dry them. Long term it's no so much an issue with bearings as grease is ever present. It's good dropping a film of oil over the surface of the treated parts but consistence in doing so every time the lathe is used may start to lapse in time ?

All said and done this looks a great solution to remove rust from those hard to reach places and sure does save some hard work on those fingers and thumbs.

I'm just using mineral spirit and cloth to degrease, but only doing this locally on the area I want to clean.   Post cleaning I'm putting a coat of light machine oil on to protect the newly cleaned parts.    I try to be religious about cleaning and oiling my lathe at home after every use and keep it covered with a dust sheet when not in use, mainly to protect from the abrasive dust from the grinding machine and cutting/cleaning in my vice.