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  1. #1
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    Default Rust removal by electrolysis

    I saw some vids on youtube re rust removal with a battery charger. I would like to give this a job but on a slightly larger scale - i.e an old 6 cyl engine block. Has anyone on here given it a go before? Will I need two battery chargers for a larger piece or will one do it? Instead of using a battery charger (I don't know if mine is suitable) could I use a 12 or 24v power supply instead? Where would I be able to buy one of these? A quick search of youtube only yielded PC power supply units which didn't look suitable.

    Brendan

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    Quote Originally Posted by 19brendan81 View Post
    I saw some vids on youtube re rust removal with a battery charger. I would like to give this a job but on a slightly larger scale - i.e an old 6 cyl engine block. Has anyone on here given it a go before? Will I need two battery chargers for a larger piece or will one do it? Instead of using a battery charger (I don't know if mine is suitable) could I use a 12 or 24v power supply instead? Where would I be able to buy one of these? A quick search of youtube only yielded PC power supply units which didn't look suitable.

    Brendan
    12V or more is unnecessary for electrolysis.
    The reason battery chargers are used is because they are cheap but 12V is more likely to generate larger sparks which combined with the large amounts of hydrogen generated can be dangerous.
    Most modern battery chargers will not work unless they are attached to a battery. Attempts to circumvent this on a battery charger is likely to ensure a meltdown of the charger.

    Electrolysis can be done successfully at around 3V (this is also less likely to spark) but what you do need for large pieces or if you want it to happen quickly is higher currents.
    I do all my electrolysis using a 6V, adjustable current, power supply which provides a max of about 5A.
    I typically use around 2A which is plenty and I get extra control of the current by adjusting the concentration of the washing soda solution.
    2A will generally de-rust something that is light rusted and fits in a 10L container, overnight.
    For bigger objects you will need higher currents - at least 10 or maybe 20A.
    20A+ DC power is usually provided by going to higher Voltages like 48V, so a low V high current PS is not going to be a cheap buy.

    What about an old welder?

    Suggestions
    What every you do, for such a large piece a lot of Hydrogen will be made. I recommend using a flat open container rather than something like a tall narrow drum.

    Always turn the power off before connecting and disconnecting and use plenty of ventilation. i.e. veranda or very large shed.

    Don't use alligator clips as they can slip off and make sparks.
    All my connection to the workpiece and other electrodes are hard mechanicsl e.g. using a bolt or screw and a ring connector crimped onto the leads - if required drill and tap and thread the workpiece to facilitate this.

    For the positive (sacrificial) electrode avoid metal as this can generate heaps of scum which will make a BIG mess and coat the electrode with a mon-conductinve film.
    Over time the film prevents current from being conducted and that means every hour or so you will need to wipe scrape the film off.
    The best thing to use are carbon arc welding rods available from large welding shops. These have a thin copper coating which can be peeled off with a little care. If you leave to copper on the copper will coat your work piece.

    To get even rust removal on a large piece you will need a number of these connected in parallel. I use 4 rod hung on the side of a 10L bucket.

    Don't try to rush things - as long as there are small bubbles its working.

  4. #3
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    Hi Bob,

    Thanks for the tips.

    I have two welders I could use - one is an old goodwell transformerarcwelder, and the other is a Chinese inverterarc welder.Would these be suitable andwhich would be better?


    How many of those arc welding rods would I need to use?

    Are there any disadvantages to doing this process quicklywith lots of volts besides the risk of an explosion?Can the rust be stripped too quickly anddamage the part?

    Brendan

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    Damn you give good answers Bob.

    Phil

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    Quote Originally Posted by 19brendan81 View Post
    Hi Bob,

    Thanks for the tips.

    I have two welders I could use - one is an old goodwell transformerarcwelder, and the other is a Chinese inverterarc welder.Would these be suitable andwhich would be better?
    I would use the one with the lowest V as they will both generate heaps of Amps.
    You probably have nothing to measure the current but I would watch for the reaction rate. If it's bubbling too vigorously

    How many of those arc welding rods would I need to use?
    For an engine block I would start with 8 - 10 rods. Watch the surface to see how even the bubbling was

    Are there any disadvantages to doing this process quicklywith lots of volts besides the risk of an explosion?Can the rust be stripped too quickly anddamage the part?
    No but don't underestimate the explosion risk

    And make sure you have the connections the right way or you will quickly pit the dressed surface.

    Quote Originally Posted by Steamwhisperer View Post
    Damn you give good answers Bob.
    Phil
    Thank your taxes Phil.

    Here is an example of a flat object layout.
    (BTW This was a failed project - when the rust was finally removed there was nothing left of the threads so I just tossed the lot out)
    However it does show how flat shallow object can be handled to minimised volume of electrolyte and have good ventilation.
    Yes I know I am using alligator clips but the ventilation in his case is so good H accumulation is not a problem

    Rust removal by electrolysis-img_5415-jpg

    Here's what it looked like when I first turned it on
    Note how one carbon rod just rests on another to provide extra coverage for the LHS of the object
    Rust removal by electrolysis-img_5416-jpg

    Here's after about 15 minutes.
    Rust removal by electrolysis-img_5417-jpg


    This site (http://1bad6t.com/rust_removal.html) shows
    - good electrode geometry
    - crap positive electode material (reo bar) - note scum on surface
    - use of deep/tall tank and alligator clip - increased risk of explosion
    - good connections outside the tanks - so why not use the same inside?
    Attached Images Attached Images

  7. #6
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    Thanks Bob for the info and pictures.

    Regarding the electrodes – isn’t the whole point of usingsteel that the steel gets deposited from your sacrificial electrode onto therusty part?If you use carbon rods wouldn’tyou just put a film of carbon on the part?


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    I seem to recall that there is a problem using electrolosis on cast iron. Something like depleting the carbon and causing extreme pitting. It would be worth checking before destroying a possibly irreplaceable item.

    Ken

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    If the welder doesn't work out as a power source, I just saw this power supply for sale on ebay
    150A at 6V should do the job!

    The steel from the electrodes doesn't get deposited on the work pince - unless you have have the power supply connections back to front. It's negative to the work piece and positive to the sacrificial electrodes.

  10. #9
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    Brendan,
    The electrolysis doesn't coat the old item in new steel, it converts the old oxide from one type (red, which is
    crumbly and soft) to another type (black, which is tougher and stable). I can't remember the proper chemical details of which is which.

    Any pits etc already existing will still be there. Any flakes of red rust will probably flake off and can't be saved.


    For a high current, low voltage power supply, if you are a bit handy with electronics you can convert an old computer power supply.
    Normal caution -> old power supplies contain 240V and capacitors (which can store the
    electricity) and can kill you even if they appear to be off <-.
    If you have the skills though, do a google search for "computer power supply to bench supply" or something like that. You should be able to get a 3.3, 5 and 12V supply with 3.3 and 5V being 10A (at least) and the 12 V a bit less (check the actual nameplate on the supply).


    You can use an el cheapo multimeter (from Jaycar or similar) with a 10A scale to get an idea of the current flowing and, like Bob says, add the soda till you get a reasonable current flow.

    Regards
    SWK

  11. #10
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    Default Not sure

    Because the engine block has many cavities and odd shaped sections, I doubt the electrolosis method would be very effective . It's likely to be covered in oil or muck too which doesn't help .

    I would take it to be cleaned at a engine rebuilder , they have the correct chemical baths and they do it all the time . . It will cost a bit but its better than all the mucking around involved with the DIY method .

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    Quote Originally Posted by morrisman View Post
    Because the engine block has many cavities and odd shaped sections, I doubt the electrolosis method would be very effective . It's likely to be covered in oil or muck too which doesn't help .

    I would take it to be cleaned at a engine rebuilder , they have the correct chemical baths and they do it all the time . . It will cost a bit but its better than all the mucking around involved with the DIY method .

    I'm a big fan of electrolysis but I have to agree with this.

  13. #12
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    I use an old laptop power supply, 5A 12v? I think anyway, but Mike is right, too many "shadows" in something like an engine block, unless you move your electrodes around so they are in the middle of the section you are working on. Happy for you to borrow the PSU if you want it.
    1915 17"x50" LeBlond heavy duty Lathe, 24" Queen city shaper, 1970's G Vernier FV.3.TO Universal Mill, 1958 Blohm HFS 6 surface grinder, 1942 Rivett 715 Lathe, 14"x40" Antrac Lathe, Startrite H225 Bandsaw, 1949 Hercus Camelback Drill press, 1947 Holbrook C10 Lathe.

  14. #13
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    molasses is a bit friendlier
    http://elantrikbits.com/lotus-elan-b...ngine-de-rust/

    shed

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    Yeah I will get the engine bored out so i'll just get the engine rebuilders to clean it - however I will be derusting a steel front end too so the info in this thread is all worthwhile.

    Thanks for the offer of power supply ueee. I might take you up on that.


    Thanks for the links Snowy and SWK - I will check themout.


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    I wouldn't do the front end with electrolosis either. There is a high chance of hydrogen embrittlement. Would not be nice having springs, frontends or axles breaking because of the embrittlement. This has been discussed on some old car restoration sites and the molasses system is the better and safer way to go.

    Ken

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