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Thread: etching or epoxy primer on bare sheet metal

  1. #1
    Join Date
    Aug 2005
    Location
    Edmonton Alberta Canada
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    1

    Question etching or epoxy primer on bare sheet metal

    I have removed the paint down to bare sheet metal and I need to know if I should use a self etching primer or an epoxy primer.

  2. #2

    Default

    If you need to do filler work you should use epoxy. You can not apply body filler over etching primer. Just be sure to get it done ASAP, it doesn't take more than a 1/2 hour for rust to start on the surface.
    Chris'
    Autobody
    Restoration
    Service

    www.carsofcomfrey.com

    Comfrey MN

    William McCormick "I am not an expert, but I do know some basics that are often not known by many."

  3. #3
    Join Date
    Apr 2005
    Location
    Far North Coast NSW Australia
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    Default

    dont forget to treat the bare metal with rust converter (phospheric acid and water:1 part to 10 ) before anything. It will actually act as an etcher for good filler and primer adhesion too.

    GJM

  4. #4

    Default acid

    This Phospheric acid and water:1 part to 10 solution where do you get the Phospheric
    Does Eastwood have this acid or get it at the local paint store??

    I am more or less doing the same thing have a 65 GTO removing the paint/bondo from the quarters. I have left the one quarter unpainted bare metal for a couple of weeks now. It will need extensive bondo work and a little welding to repair some drill holes for the bondo to stick better.

    I see no rust on the bare metal but it is pretty cold and dry here now in the Midwest and am running a dehumidifier in the garage to keep it real dry.

    I cant spray primer in the garage as the fumes will go in the house too easy I read somewhere I can get a roll on epoxy primer and will try it. So I will try this acid solution before I paint it..
    Thanks
    Eric

  5. #5
    Join Date
    Apr 2005
    Location
    Far North Coast NSW Australia
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    44

    Thumbs up phospheric tips

    Phospheric acid is the active ingredient in your commercial rust converters like 'Rust Buster' etc. Eastwood does have a few, like 'Rust Dissolver' and 'Oxisolve' but im not sure of the active ingredients in them as i have never tried them. I would say that these products do the same job although Oxisolve leaves a zinc phosphate coating which is what you need on your bare panels while they wait for repairs and a primer coat. Metal in some environments will begin to corrode in the space of 20 mins i have been told, so it is crucial to interupt the process asap.


    The standard phospheric acid rust converter solution leaves behind a milky, powdery haze on the metal and turns any oxidated areas a black colour which represents that it has chemically converted the iron oxide (rust) into an inert and more stable substance, thus temporarily stopping the rust process. Note: Temporarily.

    The best way to apply it to bare metal is from a spray bottle after mixing water with the solution at 10:1. Spray on, let it almost dry then wipe over the metal with a wet, clean rag, then a clean dry rag. A milky powder will form on the metal in a short time while any previously rusted areas will turn black. This milky powder needs to be rinsed off, preferably with wax & grease remover before priming. A slight haze will remain when the panel dries and a slight etching effect will remain which promotes good adhesion of primers, etc.
    It is not pleasant or desirable to breathe in the acidic vapours it gives off while it is working and make sure any solution is washed off your hands or anywhere else on your skin it may contact. Basic safety precautions as it is an acid. Do not apply it to painted surfaces as it will not dry or work.

    It works, it's cheap and it has heaps of uses for the restorer. Here in Australia it's usually available at any auto parts stores, department stores or paint outlets so i would assume the same in the US too.

  6. #6

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    I like it when these older threads get some new life to them. It means people are reading up on what has already been posted before asking the same questions again

    I do have a question for those who suggested an acid rinse. How do you know when the acid is nuetralized? Doesn't rinsing bare metal with water concern you? If rust can start at a microscopic level in <30 minutes from just the moisture in the air what about when you are rinsing, wiping with a towel, and using compressed air to dry the panel?

    Don't get me wrong, I too have used acid on rust. But I still have nightmares of when the car will come back to me with peeling paint or holes in the panels
    Chris'
    Autobody
    Restoration
    Service

    www.carsofcomfrey.com

    Comfrey MN

    William McCormick "I am not an expert, but I do know some basics that are often not known by many."

  7. #7

    Default

    I started restoring my 68 Olds ninety-eight convertible over 4 yeaars ago and stripped every panel to bare metal inside and out ,manfactured and replaced all the rusted panels . As i only have time in the winter to work on it I used phosphoric acid wash when i finished an area . Remember that it is in a heated garage ,I am still working on it right now and have not primed any of it and it shows no! evedience of surface or dust RUST. But I will finish sand it completly before I start to Paint .

  8. #8
    Join Date
    Apr 2005
    Location
    Far North Coast NSW Australia
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    Thumbs up water worries

    Quote Originally Posted by CARS
    I like it when these older threads get some new life to them. It means people are reading up on what has already been posted before asking the same questions again

    I do have a question for those who suggested an acid rinse. How do you know when the acid is nuetralized? Doesn't rinsing bare metal with water concern you? If rust can start at a microscopic level in <30 minutes from just the moisture in the air what about when you are rinsing, wiping with a towel, and using compressed air to dry the panel?

    Don't get me wrong, I too have used acid on rust. But I still have nightmares of when the car will come back to me with peeling paint or holes in the panels
    I know, it sounds weird to introduce water when you're trying to eradicate rust, but all the water does is neutralise the acid and you dry it off anyway and the chemical reaction that has just occurred is protecting the metal from that point on. You know the process has been completed when the milky hazed powder is present on the metal.The microscopic return of rust will probably be retarded enough after this process and give you ample time to seal the metal with primer.

    As the panel will soon be primed and painted, this means that 2 of the 3 elements needed for oxidization will be prevented from being added to the mix-oxygen & water. When oxygen, water and the metal combine, rust is the by-product of a catylictic reaction so it stands to reason that if one or two of these elements are stopped, then rust will be 'postponed'.

    Rust can never be completely stopped, but proper prep and paint will slow the process down to an almost negated level that should last many years...but not forever. You will get the peeling paint from moisture left on the panel before prime or paint and even from uncured bondo or bondo with moisture trapped somewhere. I avoid any filler work if the weather is damp or raining or overly humid as moisture will always be present on the panel then. Leading will also corrupt the topcoat if it's flux residue is not properly neutralised before priming etc.

    It's all very exciting indeed!

    GJM

  9. #9
    Join Date
    Apr 2005
    Location
    Far North Coast NSW Australia
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    Thumbs up more phos acid tips and tricks

    Quote Originally Posted by rocwal
    I started restoring my 68 Olds ninety-eight convertible over 4 yeaars ago and stripped every panel to bare metal inside and out ,manfactured and replaced all the rusted panels . As i only have time in the winter to work on it I used phosphoric acid wash when i finished an area . Remember that it is in a heated garage ,I am still working on it right now and have not primed any of it and it shows no! evedience of surface or dust RUST. But I will finish sand it completly before I start to Paint .
    Im currently fabricating new panel sections for the rusted out tailpan structure on my 53 Pontiac. When i start any fabrication with panel steel i always give the fresh piece of new metal a spray of the phos. acid solution before i begin the first cut so i have metal that is protected against oxidisation through moisture and even oils from my hands while i work it. I can then put any work aside if needed and it will always be rust free while waiting to be finished.

    GJM

  10. #10

    Default

    Quote Originally Posted by GJM
    Rust can never be completely stopped, but proper prep and paint will slow the process down to an almost negated level that should last many years...but not forever. You will get the peeling paint from moisture left on the panel before prime or paint and even from uncured bondo or bondo with moisture trapped somewhere. I avoid any filler work if the weather is damp or raining or overly humid as moisture will always be present on the panel then. Leading will also corrupt the topcoat if it's flux residue is not properly neutralised before priming etc.

    It's all very exciting indeed!

    GJM

    Exactly. So why, with the cost of materials and your time, would you risk the success of your project to a gamble like this process???
    If cutting out the effected area and replacing with new metal is not feasible then why not sandblast, use etching primer, and epoxy before your filler work. The etching primer (a true 2-part etching primer) will stop any minute corrosion in the deepest pits of the blasted metal as it sacrafices itself to protect the corrosion from spreading (rust creap) and the epoxy creates a seal between the metal (or etching primer) and any porus fillers and primers.
    Chris'
    Autobody
    Restoration
    Service

    www.carsofcomfrey.com

    Comfrey MN

    William McCormick "I am not an expert, but I do know some basics that are often not known by many."

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