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pmillen

Removing Rust From Cast Iron With a Conductive Solution

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I burned the seasoning off of one of my cast iron grates and then left it out in the rain a few years ago .  (Yes, I know, dumb me.)  I documented the cleaning process.  Recent rusted CI discussions here reminded me.

 

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I decided to clean it with electrolysis using an old battery charger that I wouldn't miss if something went wrong.  I added more solution to cover the grate after I took this photo.

 

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Here's what it looked like after about two hours at 12 v/6 amps.  It's ready for re-seasoning.

 

"How To" detail taken from several web sites.

 

Required

5-Gallon Bucket

Arm & Hammer Super Washing Soda (sodium carbonate)

Battery Charger

Rubber Gloves

Sacrificial Anode(s) (rebar)

 

Process

  1. Dissolve roughly 1 tablespoon/gallon of washing soda in water.  Ensure that all the crystals are dissolved.
  2. Roughly clean the sacrificial anode(s). Not perfect, just good enough that you can get good electrical contact.  
  3. Attach the positive lead (red) from the battery charger to the steel anode(s) (rebar). 
  4. Submerge the anode in the cleaning solution; ensure that the clamp from the battery lead isn't submerged.  If it is it will be eaten away with this process.  The steel electrode(s) will be eaten away but slowly. 
  5. If you are trying to clean a large piece you will likely need more than one anode as this process almost works "line of sight."  In other words the anode and part to be cleaned shouldn't be hidden from each other, for example if you are cleaning a large piece and only have one anode, the side facing the anode will clean better than the side facing away from the anode.  You can use multiple anodes so that the piece to be cleaned is surrounded; just connect them together with wire.
  6. Attach the negative lead from the battery charger to the piece to be cleaned.   Submerge this piece.  It doesn't matter if this clamp is submerged as it won't be eaten away.  Ensure that this piece and the anode don't contact each other as this will cause a short circuit.  They should be separated by several inches.
  7. Turn on the battery charger.  If the current is too high on the battery chargers current meter there are a number of things you can do to reduce it;

                    ●  increase the distance between the part and the anode 

                    ●  dilute the solution by adding more water 

                    ●  if you have a 6/12 volt charger set it to the 6 volt setting 

      9.  The current travels through the solution and in the process flakes off the rust - the flaking/softening occurs because of the reaction at the surface of the good steel that pushes the rust off.

 

Notes:
The cleaning solution is alkaline and will irritate the skin and eyes.  Always use eye protection and rubber gloves when working with the solution and rinse off any spills. 

 

The battery charger must be completely shielded from the cleaning solution.  Make sure the battery charger is in a location where water or cleaning solution can’t spill on it.  The 6/12 volt leads from the charger are relatively safe but it is still possible to get a shock if you put your hands in the cleaning solution or touch the electrodes while the power is on.  Turning off the power to the charger will eliminate that risk. 

 

The electrolysis breaks the water down into its components; hydrogen and oxygen.  It’s explosive.  Work in a well-ventilated area and eliminate ignition sources (cigarettes, or sparks from shorting out the battery leads). 

Edited by pmillen

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That cleaned up real nice. After John had posted his restoration thread I was looking at alternate ways of restoring cast iron other than EZ Off Oven Cleaner. I wouldn't be comfortable using it, but that's just me. 

 

Quite a few YouTube videos on how to do it. Your method looks exactly like those and I'll bookmark this thread as an instructional method should I ever need to restore cast iron. Thanks for posting this. 

 

-Dom

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4 hours ago, John Setzler said:

I have been reading about the electrolysis tank method myself and i'd like to try one but i hate to go buy a battery charger.. lol

 

 

I wonder if a car or marine battery would work? 

 

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15 hours ago, ckreef said:

 

I wonder if a car or marine battery would work? 

 

 

That is what you need... it need to be a manual charger where you can set the amperage and it won't auto switch to a trickle mode....  the charger, that is... not a battery.

 

 

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Or you could just get some oxalic acid, mix it with some tap water and soak away the rust.

If that's too hard, drift on down to Harbor Freight and get some Evapo-Rust and soak in that.

Both work very well.

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