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Technical Flash rust water drops in freshly acid etched gas tank, easy solution

Discussion in 'The Hokey Ass Message Board' started by F&J, Sep 1, 2016.

  1. F&J
    Joined: Apr 5, 2007
    Posts: 13,222


    I wish I knew this a couple days ago, in our very humid climate. My tank kept getting worse due to trapped moisture and humidity, after repeating the acids and rinses.

    This was caused by failing to get tiny water droplets out of a "baffled" gas tank after an acid cleaning:

    I even tried ethanol gas with oil mixed in, but the remaining water ruined my work overnight.

    Finally found out today that if you get the acid rinsed out and neutralized with baking soda quickly, now get as much rinse water out as possible quickly, then add two bottles of dry gas.

    Slosh that around good, and drain as much as you can, then get an air hose going in the tank for 5 minutes, while rotating the tank.

    I was shocked to see bone dry inside, (not even dampness weeping from the baffle overlap seam inside there) ......but the outside of tank was still wet from super humid weather and no sun.

    Then I mixed 6 or 8 oz of gas with one small bottle of chain saw oil and sloshed that.

    I hope this saves frustration for others, .. like two days worth :)
  2. will keep this in mind
  3. F&J
    Joined: Apr 5, 2007
    Posts: 13,222


    I'm sure you get plenty of rusty tanks at your shop.
    I tried vinegar first.. so-so results. Then Evaporust which maybe was a bit better. But each night the rust got worse inside, and looked like a dark brown muddy disaster in the morning.

    Today, I really didn't want to, but I used 1 gallon of undiluted muriatic acid; slosh and set 1 hour, slosh again and set 10 minutes. That ate all the rust super clean, even heavy scaled rust. That stuff smokes a nasty mist out of the jug when you first open it or pour it, so you need to be outside, well away from anything like a car, as it will mist onto things. You also need acid type breathing mask filters.

    The tank is super nice now.
  4. OK, I give. What is "dry gas"?
    Texas57 likes this.

  5. F&J
    Joined: Apr 5, 2007
    Posts: 13,222


    In cold climates, it is a gas line antifreeze. Not used as much these days with all the ethanol blends in gas. It completely absorbs water droplets somehow, and as I found out today, as the dry gas evaporates, it does not leave any water moisture in the tank. The water was completely gone and the tank looked desert bone dry with a few minutes of air blowing in the tank.

    here is the brand I bought today at the hardware store., I was actually going to buy alcohol but they did not have it. Note that is says " water remover "
  6. Uh, never mind...
  7. seb fontana
    Joined: Sep 1, 2005
    Posts: 7,217

    seb fontana
    from ct

    Did you seal the tank with anything?
  8. F&J
    Joined: Apr 5, 2007
    Posts: 13,222


    No, I have heard of problems with each new blend of gas eating up the coatings. So I will see how a clean tank works, versus a sealer inside a "not so clean" tank.
    C. John Stutzer likes this.
  9. F&J,thanks for those tips.
  10. linechaser32
    Joined: Apr 8, 2006
    Posts: 1,149

    from Iowa

    E85 gas works well foe cleaning a tank.
  11. Thanks for this tip..i cleaned my rusty coe tank with molasses about 2 years ago and i didnt get everything out so it rusted again so i pulled the tank out this past month got some phosphoric acid and made a rotisserie,the gas tank was clean but after one night the inside turned in to a sticky varnished mess..
    I'm going to try your method kow.thanks.
  12. falcongeorge
    Joined: Aug 26, 2010
    Posts: 18,341

    from BC

    Good thing the street rod guys ran that "F&J" character outta here a while back eh? He was really "harshing the vibe" and cramping everyone's "artistic freedom" with all that "period correct" crap!:rolleyes:
    RICH B and tb33anda3rd like this.
  13. yeah the nerve of Frank to try to keep what was done back in the day on this neo traditional forum.....
    falcongeorge likes this.
  14. belair
    Joined: Jul 10, 2006
    Posts: 8,806


    Lot you guys are pretty sharp, but remember that muratic acid is BAD STUFF. Eyes and lungs are meant to last your whole life, so be careful.
  15. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,609

    Rusty O'Toole

    Dry gas = methanol = methyl hydrate = wood alcohol. A shot of methyl hydrate in your gas tank this time of year will pick up any moisture and dissolve it into the gas, which means no frozen gas lines down the road. Or maybe this isn't a problem with alcohol bearing gasohol they sell these days.

    No matter what you do or how clean you get your tank, it will rust again instantly as soon as you put gas in it. The gas is going to wash off any oil. You have to coat the tank with epoxy or some kind of sealer. I find it easier just to buy a new tank but I know this is not always an option.

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