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    body filler experiment

    Well, time to do some minimal filling here and there on e30 in a prep for the paint. Had a few dents straightened out and need to fill them smooth. Didn't know if I should epoxy prime the repair area first and than apply the filler or fill the bare metal.
    I'm using premium filler that is good for the bare metal, galvanized, aluminum etc - Evercoat Rage Gold. There are a lot of info/debate on the web ​​​​​​for this subject, mixed opinions. ​ So I decided to experiment and see for myself. prepped the metal with 80 grit, cleaned well with ppg 330 and used 2K epoxy can on the part of the sanded area and left some of it bare. Applied the filler, let it cure and beat the crap out of it with the hammer, folded the sheet in half etc
    Here is what I found: Looks like the filler actually chemically bonded to the epoxy primer and was harder to remove from the metal vs the filler applied directly to the bare metal. Figured I'd share. Those 2k epoxy primer cans are great for spot priming as well. Once mixed, can stays good up to a week...just clean the nozzle after the use.



    The picture. The chipped area on the left side was not coated with primer, the filler came of clean when the metal was stretched. Middle chipped area still has epoxy/filler mess and was harder to scrape off










    Punishment as it looks from the other side


    Last edited by zaq123; 02-23-2020, 04:36 AM.

    #2
    Thanks for the info!

    Makes sense since most good primers are self etching, they actually "eat" into the metal and bond far superior to sanding marks (even at 80 grit).

    To add, I have used weld through self etching primer and that stuff is awesome to keep the oxidation down in blind holes/corners, as well as a great bind to the bare metal - all while being conductive and clean enough to get a good root weld.
    john@m20guru.com
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    Transaction feedback: Here, here and here. Thanks :D

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      #3
      Originally posted by ForcedFirebird View Post
      Thanks for the info!

      Makes sense since most good primers are self etching, they actually "eat" into the metal and bond far superior to sanding marks (even at 80 grit).

      To add, I have used weld through self etching primer and that stuff is awesome to keep the oxidation down in blind holes/corners, as well as a great bind to the bare metal - all while being conductive and clean enough to get a good root weld.
      2 part epoxy primer is not self etching, it basically is a glue that bonds to the metal unlike self etching that eats into the metal (acid) as you said. Unfortunately you are not supposed to apply the filler or any glaze to the self etch (almost all manufacturers specifically state no self etch). I guess there is a reaction between the acid and the filler chemicals that results in a failure at some point.

      regarding the experiment, I did glaze the entire surface (with and without epoxy) with the filler first, followed by the thin layer of the filler. However it appears that the epoxy has stronger bond to the metal, possibly due to the smaller authorized particles during spraying vs. a spread of the filler on the surface. At the same time, chemicals in the filler eat into the epoxy.

      Last edited by zaq123; 02-22-2020, 06:10 PM.

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        #4
        oi, I love science. Thank you for the correction on self etching. I am a fabricator, suspension and engine builder by trade. I can certainly paint smooth, but, lothe it like a plague, not overly versed in chemical mixing when it comes to beatification.

        The primer I mentioned is from a rattle can, not two part, never get old learning a new thing every day. :)
        john@m20guru.com
        Links:
        Transaction feedback: Here, here and here. Thanks :D

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          #5
          Originally posted by ForcedFirebird View Post
          oi, I love science. Thank you for the correction on self etching. I am a fabricator, suspension and engine builder by trade. I can certainly paint smooth, but, lothe it like a plague, not overly versed in chemical mixing when it comes to beatification. The primer I mentioned is from a rattle can, not two part, never get old learning a new thing every day. :)
          they make rattle can epoxy primer as well. Great for spot priming. Once mixed, stays good about a week until cures in the can. There is a catalyst chamber inside, punctured from the bottom of the can and shaken well, epoxy primer ready to go Click image for larger version

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          Last edited by zaq123; 02-23-2020, 04:25 AM.

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            #6
            What weld through etching primer do you guys use? Is weld through primer adequate enough to keep surface rust at bay on a project car stored inside (not outside in the rain)?

            I'm assuming you can spray epoxy primer over weld through etching primer?

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              #7
              Guess we will find out when "Project Binky" is painted. They have been using it for the entire project. Weld through primer just has zinc in it to transfer the electrons through the coating.

              Yes, it works great to keep rust at bay. Several years ago I started a shaved bay project on a spare shell I had and used weld through, never rusted in my shop that sees super high humidity here in South Florida when the new owner took possession a few months ago. Sat for years.
              john@m20guru.com
              Links:
              Transaction feedback: Here, here and here. Thanks :D

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                #8
                on the subframe reinforcement, camber plates etc I've used SEM weld thru which was discontinued and replaced by SEM ZIncweld. I would not us the epoxy paint over anything acid (primer, rust converter etc etc) but you can check with your epoxy primer TSB and see if it's compatible. Keep in mind that self etch is basically a mix of phosphoric acid and zinc. It really doesn't completely stops rust, just keeps it at bay. I actually used HD cavity wax to cover all those primed/welded/unreachable areas after the welding. If the straw could get there, it got coated. Epoxy paint is actually seals the metal and will keep it from rusting. I have a dime size area on my Jeep's fender corner where the deer's velvet took the paint to bare metal (while the deer itself took my bumper). The area is sort of hidden so I cleaned and just sprayed some epoxy primer over it and it has been 4-5 years of salty winters now, not a hint of any failure or rust.

                Why are you using Rust Thru where you can paint it? Typically Rust Thru primer is used in the areas where you won't be able to reach after the weld (between layers, hidden spots). If it's in the area where you are able to reach with the paint gun, just grind down the weld smooth (iff needed on the panel etc) and epoxy the bare metal.

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                  #9
                  NEVER filler over bare metal.

                  Even with Evercoat Rage (which sands very nicely, thank you very much!)

                  Filler's porous, and if any water gets in ANYWHERE, it'll then rust the metal underneath, and pop the filler.
                  So I take it back- you can use filler over bare metal on a Prius. But don't do it to a 2002 or E30.

                  Yes, I've learned this the hard way.

                  Etch primer, epoxy, a scuff, filler, sand the filler, and if you cut through to bare metal, spot- prime it
                  with epoxy before you filler again, or use a 'high build' primer, which is also porous.

                  Etch primer is great over smooth metal. But if you've been hammering and sanding on it,
                  just scuff the rest of the panel pretty good with anything under 400, and epoxy primer it.
                  If it's been abrasive blasted, DON'T etch prime, as the primer will be TOO aggressive, and cause problems (ironically, a different kind of corrosion)
                  If it's been soda blasted, then DO etch prime.

                  No experimentation needed- body shops have proven this stuff time and time again.

                  t
                  painted a car three times, once.
                  now, sometimes I just mess with people. It's more entertaining that way. george graves

                  Comment


                    #10
                    Originally posted by TobyB View Post
                    NEVER filler over bare metal.

                    Even with Evercoat Rage (which sands very nicely, thank you very much!)

                    Filler's porous, and if any water gets in ANYWHERE, it'll then rust the metal underneath, and pop the filler.
                    So I take it back- you can use filler over bare metal on a Prius. But don't do it to a 2002 or E30.

                    Yes, I've learned this the hard way.

                    Etch primer, epoxy, a scuff, filler, sand the filler, and if you cut through to bare metal, spot- prime it
                    with epoxy before you filler again, or use a 'high build' primer, which is also porous.

                    Etch primer is great over smooth metal. But if you've been hammering and sanding on it,
                    just scuff the rest of the panel pretty good with anything under 400, and epoxy primer it.
                    If it's been abrasive blasted, DON'T etch prime, as the primer will be TOO aggressive, and cause problems (ironically, a different kind of corrosion)
                    If it's been soda blasted, then DO etch prime.

                    No experimentation needed- body shops have proven this stuff time and time again.

                    t
                    painted a car three times, once.
                    you will have a hard time finding a body shop that epoxy prime the repair before the filler. Unless the entire car/panel was blasted and epoxied to prevent flush rust.....no shop will bother.
                    production production production hence premium body fillers are formulated with zinc so they are 100% ok on the bare metal. In fact manufacturer's TSB specify just that....nowhere do they mention e-coat or primer as a substrate.....hence my experiment

                    http://www.evercoat.com/images/ePIM/..._2_2015_EN.pdf

                    etch primers is old news that any reputable restoration shop haven't used it in a decade....so I've been told. Apparently oxidation (corrosion) of the selfetch never stops under that paint and there is a chance that you final product will fail in years to come...

                    Regarding filler and water....obviously the filler should no be exposed to water...one needs to prime seal and paint over it to protect it from moisture....just like one would need to do with any unrepaired steel body panel the car consists of ...
                    Last edited by zaq123; 03-02-2020, 02:48 AM.

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