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Thread: preventing rust before paint?

  1. #1
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    Exclamation

    Anyone else notice the index dates are off and that new topics aren't being posted?

    I sent Neil an email. What up?

  2. #2
    Join Date
    Aug 2005
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    Post preventing rust before paint?

    OK, so how do you restoration guys do it? I've been using the electrolytic rust removal thing. It works great by the way, along with ultrasonic cleaning. I've been spraying on WD40 immediately after water rinsing to keep the surface rust from instantly appearing. If I can't get back to it quick I follow w/LPS3 inhibitor.
    Now the question: What do you do after you cleanup prior to painting to keep the surface rust from appearing? The preventatives need to be cleaned off or the paint/primer won't stick. The rust appears before I have a chance to hit it w/primer. Small stuff's OK, but bigger pieces are giving me problems.
    Cadwiz in LA

  3. #3
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    if you are getting rust after you have cleaned with electrolysis it is possible you need to keep it in longermuch longer.
    leaving it to soak for awhile with the charger on doesnt hurt the part.
    you should get a black oxide on the part ,which is almost protective
    - well for a while,i have a couple of things knocking around that i have not gone further with,still black, no red rust despite the humidity,and handling ect.
    I then use naval jelly, followed sometimes by zinc paint,orzinc chromate.
    for bright stuff,i had an old bayonet i cleaned up and coated with danish oil ,no rust yet.

  4. #4
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    Aug 2005
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    I don't think it's the initial cleaning step. I have the black stuff coming out of the bath, rinse and brush/scotchbrite under water. Rust is gone and I get a nice finish which I can protect with WD40 or longer w/LPS3. It's after this step when I want to paint that the problem develops. I clean off the WD40/LPS3 with something like acetone or alcohol so the primer will stick. As soon as I do this the surface rust starts appearing (as in set the rag down, reach for the primer, look back and light rust is forming). I'm in south Louisiana so it's humid which compounds the problem. I just figured putting primer over very light surface rust would eventually lead to further rusting and paint flake problems. I was hoping you restoration guys had some fancy trick to prevent this.
    Cadwiz

  5. #5
    Join Date
    Dec 2003
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    Regina and Assiniboia, Saskatchewan
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    Post

    Cadwz...I also built an electrolytic cleaner.
    You mentioned that you have the most problems with larger pieces.
    It sounds to me that you need to leave them in the tank longer (as was mentioned above)
    Ive done some truck parts that where rusted beyond belief. Some went through the tank two or three times before rust stopped popping out.
    When I get them where I think the rust is gone, I coat them with a POR-15 product called "Metal Ready". Let it soak until it turns grey and is totally dry. Some areas need multiple treatments.
    I neutralize the Metal Ready with distilled water and dry it with heat right away.
    I don't have the humidity problem that you do so I'm not certain if this will help.
    Russ
    I have tools I don't even know I own...

  6. #6
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    Mar 2003
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    using a junk 12 volt battery charger i get the impression that it just doesnt put out
    the current needed for big bits.

    I understand some people use a dc welder to get the current up .

    I am always on the look out for a bigger 12 volt source but never find one.maybe one of the big wheel around battery chargers would work, though if has any fancy control electronics they need by passed

    last part i did was an iron coupling that attaches the wet exhaust to the manifold ogf a marine engine, it took 5 days and 2 nights ,at 12v 10 amps on abattery charger, before it was inert-ie no more rust.to give some idea of time , this part was maybe 4 pounds.

  7. #7
    Norman Atkinson Guest

    Post

    I think that the cure is to phosphate items.
    Traditionally, car bodies were de-rusted with a mixture of hydrochloric( muriatic) acid and phosphoric acid.
    This appears in many tradenames but try it.Go to a vehicle finishers shop rather than a store. Again, omit the WD 40 for this.
    Immediately, you should start overcoating!

    Norman


  8. #8
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    Independent principality of Sinquefieldia (formerly Missouri)
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    The rust issue is NOT pits....

    I know what he is saying, the rust forms in dustty orange sheets all over the part right away. Rust isn't forming where it was, it is forming on a super-clean surface. "Flash rusting".

    I end up wiping off that rust and going ahead with painting. Seems to work fine, nothing has popped out with big blisters under the paint.

    That does not seeem to happen with phosphoric acid cleaning. It takes longer for rust to form, if you dry out the part it won't be a problem.

    Seems to form the phosphate coating that Norman refers to, which used to be a normal part of auto body painting, before galvanized sheeting was used.

    1601 2045 1412 2321

    Keep eye on ball.
    Hashim Khan

  9. #9
    Join Date
    Aug 2005
    Location
    Clinton, LA
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    J Tiers has it: "flash rusting" on highly active, newly cleaned surface is the problem. So far I think I've had good results for overall "crusty" rust removal in the tank for a few hours with small to medium parts. Overnight on one stubborn larger piece. Fixing to dump a drill press head (frozen quill) in the tank which will likely take a few days. I have a big battery charger with no amp problems so far, but the head will be the biggest thing I've tried. I think what I was looking for was validation from someone that wiping off the fine layer of flash rust then painting was OK.
    Thanks for the replys
    Cadwiz

  10. #10
    Norman Atkinson Guest

    Post

    J et al,
    I was aware of depositing an actual metal coating. I suggested a classic treatment knowing that most of us cannot emulate something better. With tongue in cheek, I moved the reader away from proprietory brand names and stuck for the basic gubbins!
    So, kind sir, forgive the old fella'
    Reading over my notes and others too, might I add that using a hot air gun will effectively dry out the phosphated coating prior to coating and give better rust proofing.

    I did go off at a bit of tangent but this
    rust proofing is not merely whopping a set of coats of primer, undercoat and finish.
    Not in places where the metal moth has held
    sway for a time. It gives me the opportunity to mention " lead loading" which I explained to my good friend BillyBoy a while back. Maybe the info is still around on file but most of us have to resort to a plastic filler to hide the pitting.Digressing, I am filling my very neglected Quorn Tool and Cutter grinder for a more posh coat or two of jollop.
    It is important to add that many plastic
    fillers are far from waterproof and consequently, can allow further rusting.
    For my part, I rust proof, phosphate and then prime- and then fill- rub down and re-prime before the finish coats are applied.
    Digressing further, I spray a mist coat of contrasting paint which shows up the hills and hollows after rubbing down.

    Anyway, I hope that this adds a bit to the fund of knowledge for some.
    Kind Regards

    Norman



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