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Thread: Electrically Removing Rust

  1. #11
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    Quote Originally Posted by JoeLee View Post
    OK, thanks guys for the refresher. I knew it was a simple process.

    I have some concrete wire mesh sheets that are 6"x 6" squares, the stuff is probably 3/16" dia. wire. I could cut to fit snugly around the inside of the plastic pale as opposed to hanging rebar or metal strips. Less risk of having any shorts. How would that work??
    The whole part would be evenly surrounded by the mesh. I also have some 2"x 4" wire fence, probably 3/32" dia wire. The galvanizing has long worn off of it, it's rusty. Which should I go with??

    JL..............
    It's all about AREA and in sight of the work.

    The wire mesh has great sight lines, but might be shy on the area specification. You want at least as much anode area as cathode. More is better. do the math. Wire , not facing the work, does not count! ;-)

  2. #12
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    If you make the workpiece the anode, oxygen is liberated which cannot cause embrittlement. Check the progress of the cleaning frequently. Try to keep the froth from the electrodes from mixing, as the combination of hydrogen and oxygen makes a much bigger bang if it ignites than hydrogen alone in air.

  3. #13
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    Quote Originally Posted by old mart View Post
    If you make the workpiece the anode, oxygen is liberated which cannot cause embrittlement. Check the progress of the cleaning frequently. Try to keep the froth from the electrodes from mixing, as the combination of hydrogen and oxygen makes a much bigger bang if it ignites than hydrogen alone in air.
    That makes the workpiece the sacrificial anode. I've done that by mistake. I don't make that mistake now.

  4. #14
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    I suppose it depends a bit on what you are de-rusting, however I find the solutions you get at the hardware store used (and reused) in a plastic bin work so well it doesn't seems worth the fuss.
    .

  5. #15
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    Sightlines matter, but somewhat less than what might be expected. For example, both sides of my anode plates are heavily pitted, even though one side of each is close to and facing the side of the container. And, as far as I remember, I've never had the process fail to loosen what seem like hopelessly seized fasteners or parts seized together.

  6. #16
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    "check the progress of the cleaning frequently". Why do you think I put that line in my post, Cameron, do you think I'm stupid, I have qualifications in metal finishing.

  7. #17
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    Quote Originally Posted by old mart View Post
    "check the progress of the cleaning frequently". Why do you think I put that line in my post, Cameron, do you think I'm stupid, I have qualifications in metal finishing.
    No, I don't think you're stupid, in fact most of your posts seem to suggest a respectable degree of intelligence as well as considerable experience.

    Perhaps you could be more specific about what you mean by "frequently". I've had a part connected to positive for not much more than five minutes before I thought to check on it and it was a mess. It's a good thing it wasn't something very important.

    This was using a 10 amp battery charger, not a 300 amp welding machine.

  8. #18
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    Quote Originally Posted by cameron View Post
    No, I don't think you're stupid, in fact most of your posts seem to suggest a respectable degree of intelligence as well as considerable experience.

    Perhaps you could be more specific about what you mean by "frequently". I've had a part connected to positive for not much more than five minutes before I thought to check on it and it was a mess. It's a good thing it wasn't something very important.

    This was using a 10 amp battery charger, not a 300 amp welding machine.
    So are you saying that if you leave the part in there too long the process can start to eat away at the base metal??
    In a previous post Cal mentioned he left the parts in for 8 to 12 hours. I would never leave anything that long with out checking frequently to get an idea of how long the process takes for my particular part.

    JL...........
    Last edited by JoeLee; 07-16-2019 at 08:00 PM.

  9. #19
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    Quote Originally Posted by JoeLee View Post
    So are you saying that if you leave the part in there too long the process can start to eat away at the base metal??
    In a previous post Cal mentioned he left the parts in for 8 to 12 hours. I would never leave anything that long with out checking frequently to get an idea of how long the process takes for my particular part.

    JL...........
    You have likely heard of the term "sacrificial ANODE. But never the term "sacrificial cathode".

    That is the difference.

    The anode is required to "give up" material , The negatively biased cathode is not giving up the base material, It;s only shedding rust (while gaining smut ;-)

    You can leave most any work piece in the "reaction" for as long as you wish as long as the part you value is not the SACRIFICIAL ANODE. Clear as mud, right?

    Also, mind the amps. I was running under two amps for a part of some few tens of square inch area. Maybe two square feet tops.

    Throw an old cast iron brake rotor on the cathode hanger and see what you are getting for values before putting the expensive work into the fray.

    I would go for 5 amps for such a crude chunk if the battery charger would drive that. I guess a 24 Volt X 10 or 20 Amps would be a nice supply for small scale work. Again, It's all about area.

  10. #20
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    Quote Originally Posted by JoeLee View Post
    So are you saying that if you leave the part in there too long the process can start to eat away at the base metal??
    In a previous post Cal mentioned he left the parts in for 8 to 12 hours. I would never leave anything that long with out checking frequently to get an idea of how long the process takes for my particular part.

    JL...........
    I'm saying that as soon as you put the part in the tank and connect the part to positive DC the part is being eaten away. Obviously whatever you have in the tank as a sacrificial anode has to be connected to negative DC for this to happen. I am not able to tell you at what rate the part will be eaten away.

    I'm not asking anybody to believe me, I don't even believe half the things I post here.

    Try it for yourself.

    If you reverse the connections so that the part is neg. and the sacrificial anode, um, is the sacrificial anode, that is, connected to positive, the part will not be eaten away. But the anode will be.

    The anodes in my main tank are roughly 6"x25" and were originally 0.101" thick. These have been in intermittent use for several years. They are now deeply pitted and each of the two has at least two perforations. There may be more holes blocked by rust, and I expect many more in the near future. About time for replacement.

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