Electrolysis de-rusting FAIL - Woodworking Talk - Woodworkers Forum
 
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post #1 of 12 Old 02-05-2018, 09:59 AM Thread Starter
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Electrolysis de-rusting FAIL

I have an old bench grinder that I'm restoring and there's a few pieces of hardware that needed rust cleaning. Tool rests and brackets and such. So, I figured I'd try the electrolysis approach that I've read about but haven't done yet.

Started with a 4 gallon plastic bucket, filled 1/2 way with water and mixed 1/4 cup of washing soda. I have a couple sheetmetal panels about 4x6 inch and put them on the bottom as the sacrificial electrodes. I hung the parts to be cleaned from a piece of threaded rod with 14 gauge wire (stripped Romex).

There were 5-6 pieces 2" square to be cleaned. Attached my 6 amp battery charger to the wires, and it went off scale and popped its breaker. Hmm. Double checked that nothing was shorted (you can't see through the electrolyte). Nope.

OK then. I have a 30 amp DC power supply that I use for car audio projects, so I hooked that up. It immediately went into current limit and shut down. Huh?

Brought out the big gun - my 100 amp car battery booster. The electrolyte started bubbling and a few seconds later the 14 gauge wires got red hot and set fire to my bucket

So... umm... what did I do wrong? There were no shorts.

Dave in CT, USA
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post #2 of 12 Old 02-05-2018, 10:45 AM
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I de rusted a panel saw blade using the same method. I used a large allen wrench for my sacrificial electrodes. I don't remember which (+/-) jumper cable went where, but I do remember that when I turned on the 10 amp charger, I could see the rust bubbling off of the saw blade. It took several hours (maybe 10) and It left the blade blackened. I had to scrub the black off the steel, which took a lot of time and elbow grease.

I did find a product sold at harbor freight called Evapo-Rust, Which does work well. It will not harm paint, and only removes rust...no nasty smell, and is bio degradable. I used it on an antique hand plane that I soaked overnight, then washed everything off and re oiled. I would recommend using it if practical, and when you are done you can poor it back in the bottle and re use it several times.
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post #3 of 12 Old 02-05-2018, 11:09 AM
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Photos of your setup might help figure this out. I've done it a few times with no issues.

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post #4 of 12 Old 02-05-2018, 11:48 AM
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You might need a ballast resistor in the form of a light bulb in series to protect the equipment.
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post #5 of 12 Old 02-05-2018, 02:10 PM Thread Starter
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I should've taken photos, but didn't. There was a LOT of current flowing, that's for sure. Enough to turn 14 gauge copper wire into a light bulb.

I thought maybe there was too much surface area but if gmercer has done it with a saw blade, it's not that. Maybe I mixed too much washing soda, and the water was too conductive? The web page I got instructions from said 1/3-1/2 cup for 5 gallons so 1/4 cup for 2 gallons should've been OK, no?

I'll try this again in the future with a bigger bucket. Meantime the parts have been cleaned with a wire wheel. Oh well.

Dave in CT, USA
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post #6 of 12 Old 02-05-2018, 03:14 PM
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Do you have a current adjustment on your charger? Turn it down to less than 1 amp, or use a nearly discharged car battery instead. The problem is too much voltage.

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post #7 of 12 Old 02-05-2018, 04:56 PM
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When I was a kid I used to mess around with carbon arc welding using the carbon rods from d-cell batteries and salt water, just a little too much salt would blow the house fuse every time (yes, it was plugged into the wall outlet). I think your problem was too much soda. Your water hardness/ mineral content might be high so you need less soda to conduct current.
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post #8 of 12 Old 02-05-2018, 05:20 PM
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I've had very good results using oxalic acid mixed in hot water (4 table spoons per gallon of H2O). The electrolysis method seems complicated and messy. Oxalic acid can be pour down the drain. The local Ace Hardware has it, it's used to bleach wood decks and is sometimes called "wood bleach".

As for it's toxicity, don't drink and use rubber gloves and you'll be fine:

What foods are high in oxalic acid?
Lists of foods high in oxalic acid vary greatly from source to source. The body is known to absorb oxalic acid from only a handful of foods, according to the University of British Columbia, including peanuts, pecans, wheat bran, spinach, rhubarb, beets and beet greens and chocolate.

Last edited by P89DC; 02-05-2018 at 05:23 PM.
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post #9 of 12 Old 02-06-2018, 08:19 AM Thread Starter
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The more I think about it, the more I'm convinced there must have been a dead short between one of the pieces hanging in the bucket and the sacrificial electrodes. It must've been like 40 amps to melt 14 gauge wire. Will use a different bucket next time, if I ever try this again.

Dave in CT, USA
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post #10 of 12 Old 02-10-2018, 06:52 PM
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You most likely had a short between the pieces being derusted and the anode pieces. I do quite a bit of electrolysis, and never add anything to the water, just lash it up and let it run all day. A small battery charger and a 12 volt battery works fine. One caution on the sheet metal panels - don't use galvanized. Remember that the action is mostly line of sight - from the part of the piece being derusted to the anode. Thus it helps to reposition the parts occasionally.
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post #11 of 12 Old 02-11-2018, 02:00 AM
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Quote:
Originally Posted by Maylar View Post
The more I think about it, the more I'm convinced there must have been a dead short between one of the pieces hanging in the bucket and the sacrificial electrodes. It must've been like 40 amps to melt 14 gauge wire. Will use a different bucket next time, if I ever try this again.
Your setup lacks resistance, it shorts via the water (of course water is highly conductive, with or without soda. If you put a hot lamp socket or a hair dryer into a bathtub it shorts as well, and this setup is effectively the same!). Voltage is not the problem. Gary Beasley's comment is correct, you need a resistor placed in series in the loop. For a 12V battery charger (or an old PC power supply, they're great for this if you use the 12V rail) you use a simple 12V car light as resistor. It's much easier if you have a socket for the light and can connect the wires to the socket. Connect one of the wires from the battery charger / power supply to one of the poles on the 12V light socket, and run a separate wire from the other pole of the lamp socket to the top electrode (the threaded rod with 14 gauge wire that your piece hangs from). The sacrificial electrodes stay connected (directly with a wire to the power supply) as you already had them. The 12V battery included in Alchymist's setup is not necessary, I'm not sure what function it would serve (hard to see in the pics but it looks like it's placed in parallel rather than series in his setup, if so the current would mostly bypass it). Alchymist's battery charger may have a built-in protection/resistance that prevents his setup from shorting, or the battery is in series after all and functions somehow as a (somewhat odd) resistance. It may be better there also to place a 12V lamp - in series, not parallel! - in the loop and to remove the car battery.

The 12V light will come on as you run the setup, and yes it is very convenient for rust removal (plus it preserves your work piece as it's non-abrasive/corrosive). My setup uses 3 short rebar rods at equal distance along the sides of the bucket as sacrificial electrodes, with the work piece hanging in the center. That reduces the line-of-sight/shadowing problems.

I learned all this the hard way - blew a few battery chargers myself before researching the issue and getting it right!
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post #12 of 12 Old 02-11-2018, 12:12 PM
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Tungsten bulbs are great for this application because the filaments resistance goes up as it gets hotter, giving a bit of current control.
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