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Electrolytic Tank Rust Removal

Discussion in 'Maintenance and Servicing' started by buckett, Sep 29, 2012.

  1. Hey guys, I thought there might be a few people on here interested in this. Has worked INCREDIBLY well for me. Although not at first as the current didn't get through the tank paint until I moved the clip.


    my set up

    and the progresss!!


    I should probably start a project thread but I'm a bit shy about my complete lack of mechanical knowledge...
  2. Few more comparison shots might show it a little better...
    Good to hear the electrolysis works for you though!
  3. Just make sure not to get the wires the wrong way around ;).

    Personally I find phosphoric acid to be a quicker, easier method of removing rust - any particualr reason you went with the electorlytic option?
  4. I forget my chemistry. Does electrolytic reaction act against the original rust or just remove it?
  5. It reverses the process - so the rust is converted back into steel.

    However, since the rust does not bond very strongly to the metal all but a very, very thin layer will be removed. Acid treatment is similar, but leaves a very thin layer of zinc on the surface of the metal rather than raw steel. Of course not everything can be treated with acid.
  6. I needed a battery charger anyway and it was the cheapest option. Also looked kind of cool and I wanted to see if it would actually work! Can you recommend some kind of tank lining product for me?
  7. But zinc being significantly more reactive than steel would then itself oxidise quite quickly, would it not?
  8. Where does the zinc come from? I thought acid treatment would just be applying phosphoric acid to it?
  9. And even though I don't know any electrochemistry, and have never attempted rust removal from a petrol tank....

    I'll chime in and say, it is probably best that you get in clean then and seal the petrol tank very soon after doing this electrolytic rust removal... the surface is probably going to be a bit porous and very clean... and will re-rust very quickly (I strongly suspect this is the case)
  10. Yes the zinc is more reactive, but its oxide product forms a protective film in exactly the same way as aluminium does. The added advantage is that the zinc will act as a sacrificial anode should the tank liner get worn through or not completely cover the inside of the tank (same reason people attach blocks of zinc to steel boats).

    Most phosphoric acid based rust treatments will also contain a quantity of zinc phosphate in solution (or you can dissolve zinc metal in the acid prior to using it). When the rust is dissolved, creating iron phosphate, it displaces the zinc from solution and deposits it on the surface of the metal.

    So essentially the thin layer of rust attached to the surface is replaced by a thin layer of zinc - whereas electrolytic treatment replaces it with a layer of iron. However, as Magin points out this iron will start to oxidise fairly quickly if not kept completely dry, or away from oxygen.
  11. crap... how quickly? I finished it today and will order the sealing stuff now!

    Is there something i can fill it with in the mean time?
  12. Kept perfectly dry steel will keep for months, even years, without a hint of rust (I used to have metallographic specimens that proved this quite well).

    In the presence of moisture, or even moist air, even a day or two is more than enough for rust to start forming on most steel alloys. One experiment I can still remember doing as a student was polishing a piece of steel to a mirror finish - then placing a single droplet of water on it. You could actually watch the tiny patch of rust form at the centre of the droplet in a few minutes (due to an oxygen differential between the metal in air, and metal in water. Iron meteorites are even more fun, since they react extremely rapidly with even just the moisture in air (which is why all mine are encased in resin).

    The small amounts of rust that do form however might not be a problem if they're reasonably well bonded to the metal. But might be worth considering picking up a small bottle of "rust converter" and giving the tank a quick clean before using the sealant (or just by the full tank sealing kit from KBC, which includes the phosphoric acid and a degreaser).
  13. but then I'd have to admit that I maybe didn't choose the smartest method haha. 8-[ I've bought the rust blast product on an impulse to clean some other parts on the bike so I'll use that to give it a rinse before I seal i think. I imagine it should all arrive by the end of the week so should be ok lets hope.
  14. At least the electrolytic cleaning reduces the amount of acid you need to use ;).

    And it's a lot better than soaking the tank in a tub of molasses. :LOL:
  15. That old overweight professor image is returning.
  16. When we stop dredging out here with our hardened steel teeth, they are all lovely and shiny and polished to quite a gleaming state (assuming they arent covered in clay!).
    Anyway, give it less than 5 minutes and the steel has flashed to rust.
    This is worst case scenario though, wet with salt water hehe.
  17. Whatever works for you. ;) :LOL:
  18. thread about rust removal gets saucy... only on NR.:bannanabutt: