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Power supply for electrolysis

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  • Power supply for electrolysis

    Hello,

    Currently when I have rusted items I attempt to stip the rust by using the electorlysis process.

    The process, which I read in a magazine suggest using a car battery charger. I have tried that but I am currently using a computer power supply. I found this works much better over the car battery charger I was using. The computer power supply has a maximum output of 12VDC at 20A.

    My question is can I use another power supply to up the voltage? I would have to connect them in series. Can this be done using regular computer power supplies. My concerns lie in the fact that its a transformed output and that they are not like regular batteries.

    Thanks,

    Szatniasz

  • #2
    Szatniasz,

    I'm not sure about the series thing so can't give any worthy answer to that. That’s actually a very interesting question from my point of view and I hope someone can give an answer AND explain why.

    However, I do know that the higher the voltage the more "distortion" you get in the original matrix. So for instance, when museums want to convert old bronze or iron-age artifacts back from the oxide to the metal, they use low voltage over a very long period of time. This tends to preserve the original shape of the artifact better than high voltage over a shorter period of time.

    If you’re just talking about surface rust, I don’t think it makes much difference, but thought I’d mention it, just in case.

    Comment


    • #3
      Technically, the answer should be yes, but you need to isolate the two power supplies from each other and from ground.

      The AC power cord needs to have the ground tab removed or add a 3-prong ground adapter to the end of the plugs. Also, do not let the chassis of the two power supplies touch each other. They must be electrically isolated.

      The two supplies can be serially connected with one minus connected to the others positive terminal.

      Ideally, both power supplies need to be the same type to balance the current. The output current will still be the maximum rated for one supply, but the voltage will be doubled.

      Since the supplies are isolated from ground, you need to make sure you don’t have an AC component that could cause a shock hazard.

      Marv

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      • #4
        What's your hurry? A couple of advantages of the electrolysis method of rust removal are the safety to the user and the part being treated, and the controlled removal of rust with a system that requires little monitoring.
        If the rate of removal falls off, the anode may be the problem. The users suggest large surface area such as pieces of sheet metal, or rebar for anodes. Any material used must be kept clean, or the removal rate will fall off. Do not use stainless steel.
        Jim H.

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        • #5
          Thanks Marv. I'll give it a shot. I understand the threat of a shock with no grounding but I'm confused by your "AC Component" reference.

          Also, there is no hurry. This is actually an experiment to see if I can strip paint/powder coating from parts. The article I originally read mentioned that the process may be able to strip old paints. I am assuming that the paint stripping abilty comes from the fact that a hydrogen(or is it oxygen?) bubble forms in between/around the paint and the metal substrate and therefore the physical bond of the paint breaks and the paint comes off.

          Since most paints and especially powder coatings are insulators I want to see if I can seperate the paint from the part. For this I want to experiment with a higher voltage first.

          Also, the higher voltage will assist with my supended lighting experiment in the future.

          Cheers,

          Szatniasz

          [This message has been edited by Szatniasz (edited 02-18-2004).]

          Comment


          • #6
            You could build your own electrolysis power supply from an outdoor light transformer, a fan controller to vary the AC going in to the transfomer, and a full wave brige on the output of the transformer to convert it to DC.

            Outdoor lighting is 12 Volts AC. the output from the lash-up I proposed will be a big less than 12 Volts, but you can vary the voltage to suit your process. The DC won't be pure, it will have significant pulsation as you turn the fan controller down. I think that could be an advantage in electrolysis for its "cleaning action".

            You need a fan controller not a light dimmer. Fan controllers are full wave devices designed to run induction motors. A transformer is an AC induction device.

            Be sure to pick a full wave bridge rectifier with enough amp capacity to suit the transfomer.

            Comment


            • #7
              You can series hook up dc supplies as long as the outputs are not grounded. I don't think you will be able to strip paint. There are some acid solutions that will speed things up. Two parts water and one part muriatic acid will remove chrome and rust.

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              • #8
                The AC Component is called "leakage". It is checked at the factory using a test called hipot. If current from the AC line leaks the ground or other components in the PS it could provide a shock hazard.

                An example of a hipot test failure occurs when something like a cap that is tied to the AC line shorts to the ground or a transformer winding insulation breaks down and passes current to a component or chassis when it shouldn't.

                The ground on the power supply helps protect the user by shunting the AC to ground and popping a fuse.

                Since you need to isolate the ground you are severing a safety measure. Working in a liquid bath compounds the problem.

                Safest way is to get two auto batteries and try those first. ALWAYS use a fuse or breaker mounted right at the batteries terminal to avoid a fire!

                Marv

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                • #9
                  Complicated question.

                  First, I would not recommend cutting or lifting the SAFETY ground connection on any electric equipment. The green wire is a SAFETY ground and is intended to PROTECT YOU if something goes wrong. Would you use a grinder w/o safety glasses? You may get away with it a hundred or a thousand times but when something in the circuit fails you might get shocked. Please don't do it. Specially around conductive solutions with bare wires.

                  If you want to put two supplies in series, the word you are looking for in the specs is "floating". That means the output is not referenced to ground. If the output is described as floating then they can be placed in series without disconnecting any grounds. Keep the combined output voltage within reason. If you keep the total voltage under 75 or 100 V you should be OK. Higher than that and you may exceed the breakdown voltages of something. Computer supplies are mass produced and they save 1/1000 of a cent everywhere they can. Every spec of every part is examined for a chance to relax it and save fractions of a cent.

                  I assume you are asking about computer supplies because they are cheap. You can take an Ohm meter and check the output leads to see if any are grounded. Measure resistance between the + and - leads and all three wires on the AC plug. If you get a high resistance (say, over 10,000 Ohms) all ways, then it is most likely a floating supply and can be wired in series w/o disabeling any safety features. If not, try another supply.

                  PS, only the second supply, the one going from +12 to +24 volts needs to be a floating output. The output of the first one can be grounded with no problems. Actually, this would increase safety.

                  Paul A.
                  Paul A.
                  SE Texas

                  Make it fit.
                  You can't win and there is a penalty for trying!

                  Comment


                  • #10
                    The ground on the output is indeed grounded to the case ground on a computer supply as well as AC supply ground but NOT the neutral. I don't think stacking them is a good idea. In a switch mode computer supply the incoming AC is rectified and filtered with no transformer isolation. There is near 200 volts DC present in the box. If something fails in such a way that this voltage is applied to the housing with no ground it would be potentially lethal. DC is way more dangerous than AC. If this circumstance occurred then the ground output of the supply could have 180 volts on it relative to ground. Bad plan, don't do it.

                    [This message has been edited by Evan (edited 02-18-2004).]
                    Free software for calculating bolt circles and similar: Click Here

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                    • #11
                      You say the battery charger doesn't work as well as the computer power supply. If the charger is a smart type, it's waiting to detect the battery voltage before it begins to deliver a charge. That type won't work for powering anything without modifications. If the charger is the really cheap type, it will be putting out 20 volts or so already, if not loaded down with a low battery. If you can hook a 12 v headlight to it, and it lights, then you can use it. Probably all you need to do is add a capacitor across the output leads, to smooth the pulsating dc output, raising the average voltage level and thereby get a somewhat shorter 'derusting' time. Unloaded, the voltage output, in 12 v mode, and with the output capacitor, will be almost double that of two computer power supplies in series. I don't know how much current will be flowing during the derusting operation, but another way to get about 20 volts is to use an adapter rated at 12 v or more. These will also deliver nearly 20 volts unless loaded down. If the current draw is less than .1 amp, this might be a cheap and simple way to do the job. Maybe ideal for small parts.
                      Another idea, the old c band actuator power supplies deliver anywhere from 30 to about 50 volts, and are capable of a couple of amps or so. You or someone would have to bypass the relays to get constant power to the terminals. These things should be kicking around, since they're not used much anymore.

                      [This message has been edited by darryl (edited 02-18-2004).]
                      I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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