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  1. #1
    Join Date
    May 2020
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    Willowbank QLD
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    Default Post Citric acid protection

    Hello all

    I am about to give some old panels of my Chev truck project a Citric acid bath to remove some of the rust. Once they come out of the bath they will require repair that make take a few weeks depending on available time. I will be doing one panel at a time. The truck probably wont be ready for paint for a year or so.

    Therefore what should I put on the metal to protect it whilst I do the metal repairs and put it in storage for painting.

    Thanks

    Steve

  2. #2
    BobL is online now Member: Blue and white apron brigade
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    Feb 2006
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    Perth
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    Default

    What sort of repair?
    If its not welding I'd spray a Zn rich primer/undercoat on it right away.
    If its welding I'd just wipe some light oil on it, and put the Zn rich primer/undercoat on it after its been repaired while waiting to repaint
    If it comes back from repair in a rusty state - back into citric acid.

  3. #3
    Join Date
    Apr 2019
    Location
    Adelaide
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    Default

    When I had my car body sand blasted I immediately painted all the dad's metal with etch primer. As I did the rust repair sections I painted more etch primer. Etch primer will not protect against moisture so keep it dry and avoid condensation.

    You will need to neutralise the acid and flush with plenty of water.

  4. #4
    Join Date
    Sep 2005
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    Bendigo
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    Default

    Use a modern protection, epoxy primer.
    Older primers were hydroscopic and would rust under the paint. Epoxy primer will seal the surface and protect from moisture.

  5. #5
    Join Date
    Jul 2008
    Location
    near Warragul, Victoria
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    3,399

    Default citric

    I really like the Wattyl Super etch prime, it comes in grey and black , its a epoxy paint with a tough finish.

    With the citric bath, the warmer or hotter the solution is, the faster it will work, its a rather slow method in a cold environment . Its a Summertime job for us Victorians !

  6. #6
    Join Date
    Apr 2020
    Location
    France
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    1

    Default Rust Protection

    Two things I have found to be good.

    Gibbs oil is a especially made product that stops rust on any metal. Panels tools etc. It works well and can be painted over without any problems. So suits body panels, gives protection for months.
    The other is basically phosphoric acid. This brand you can get at Bunnings. It is much cheaper than Gibbs.
    Not the best phots but you can find Gibbs with Google.
    When you take the panels out of the citric bath they will "flash" rust almost immediately. It helps stop the rusif you get a heat gun on them to dry them quickly.If you wipe them over with either product straight away they can be left for months without further treatment.ranex.jpggibbs.jpg

  7. #7
    BobL is online now Member: Blue and white apron brigade
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    Default

    Quote Originally Posted by Redminch View Post
    When you take the panels out of the citric bath they will "flash" rust almost immediately.
    That's only if you wash them, its the water that does it. Unless you are going to prime or paint immediately I don't recommend washing them.
    Just blow dry with compressor and used a heat gun to get the acid out of the cracks.
    Citric acid is a chelating agent and does not dissolve steel I've done lots of testing on this

    Below shows a test run with the initially heavily rusted steel steel being dunked in various 10% acids (HCl - Hydrochloric, AC = Vinegar, Ax = Oxalic ND CI = citric) and then pulled out, blown dry and suspended in air for 6 days. NO WASHING

    6days.jpg

    Here again after 10 weeks. Oxalic acid wins hands down but the vinegar and citric have also not rusted much.
    These pieces were left hanging up under a back veranda.
    10weeks.jpg

    For general use there's no need to remove any residual like the yellow green ferrous oxalic acid layer - just paint direct over the top.

  8. #8
    Join Date
    Feb 2009
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    jilliby nsw
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    67
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    78

    Default

    Thanks for your input to this thread Bob L. Im just about to start rubbing back and repairing the panels on a '68 cooper S so this information will come in handy to preserve the finished panel prior to paint.

  9. #9
    Join Date
    Jul 2008
    Location
    near Warragul, Victoria
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    3,399

    Default prep

    I do this sort of thing in Summer. After removing the part, I do wash it down with water but during Summer that isn't a problem. Before painting with the etch prime, I go over the part with a brass cup type wire wheel mounted on a 5" angle grinder, doing this removes any left over crud and it really polishes up the surface to a nice clean bright finish. Finally use a rag and a solvent, I use thinners , and rub over the surface to remove any residue from the previous steps, lots of gunk will come off with the rag wash. Use good gloves and be careful . If i am storing the part , I wrap it in Glad Wrap , it keeps the air away . A 50 metre roll is cheap

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