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Thread: How to best remove surface rust before Epoxy primer

  1. #1

    Default How to best remove surface rust before Epoxy primer

    I have a 57 356A Porsche that the previous owner stripped the paint off of 2 years ago and then did nothing. It has been indoors but is still covered with a nice layer of surface rust, some fairly thick. Nothing cancerous, but using a DA with 80 grit is not doing much to it. I tried using Navel Jelly, Phosphoric Acid, and it worked, but took a long time and still seemed to leave a lot of rust deep in the scratches left behind from when the PO removed the paint. Looks like he used a pretty aggressive grit level when he removed the paint. I have sand blasted exteriors with great results before without warping the panels but was hoping to avoid the mess associated with this process. Any ideas? I want to get the car in Epoxy Primer but do not want to cover rust left behind. Do I need to let the Jelly work longer? If I buy the gallon of Phosphoric Acid is it more concentrated than the Navel Jelly brand? I left it on for 15+ minutes and had to do a lot of work with a brass brush to even get these results. I can't see doing this to the entire car. Thanks for the help.
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  2. #2
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    If that car was in our shop we would spray about a square foot of Picklex 20 on the surface work it in with a scuff pad then wipe it off and move to the next square foot. After the entire car was treated we would do our body work because the Picklex would protect the metal from further rust and after the body work we would scuff and epoxy prime the entire car then apply our 2K primer, guide coat, block sand and paint.

  3. #3

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    Quote Originally Posted by Len View Post
    If that car was in our shop we would spray about a square foot of Picklex 20 on the surface work it in with a scuff pad then wipe it off and move to the next square foot. After the entire car was treated we would do our body work because the Picklex would protect the metal from further rust and after the body work we would scuff and epoxy prime the entire car then apply our 2K primer, guide coat, block sand and paint.
    Len, does the Picklex 20 get the rust out of the sanding grooves and pits? After body work and before applying the EP, would you DA the entire car, if so what grit would you use? Thanks

  4. #4
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    Quote Originally Posted by merbesfield View Post
    Len, does the Picklex 20 get the rust out of the sanding grooves and pits? After body work and before applying the EP, would you DA the entire car, if so what grit would you use? Thanks
    You must remove any lose rust then the Picklex will convert/stabilize any remaining rust and, in most cases, it will make minor rust disappear. Before applying epoxy primer we would either go over the surface with some 180 or 220 on a DA or by hand.

  5. #5

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    I have done some research on the Phosphoric option and there seems to be some people who are addiment that it should not be done prior to epoxy paint. Barry with SPI is among one of those that says to never use it. I understand there are always those that do and don't do certain paint steps, but I was hoping to use his epoxy paint system. What do you think is the reason that some people have had epoxy issues with Phosphoric acid rust treatments? I just want to be sure to get it right. Thanks

  6. #6
    autobodytech43 Guest

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    not neutralizing it thoroughly can give you adhesion issues. It's just one of those things...Some people believe in using epoxy directly after sanding and leaving clean metal, and some like to use a metal conditioner. It's just a matter of opinion.
    I think if there's pits and it's not blasted or you haven't used a geared wire wheel w/ the handles to get into the pits than a conditioner is an option I'd go with. If you had it blasted or used the gear wire wheel than there's a noticeable difference in the look of the metal and you'll know it's clean, and in those cases no conditioner is needed, in my opinion. In your case, sounds like conditioner won't hurt. There's a HUUUUGE differeence in the look of the metal when it's sanded compared to how it looks when it's blasted and wire wheeled(with the right tool). Again, this is all a matter of opinion, and keep in mind, Barry sells paints and primers so he's gonna naturally say conditioners are bad. If it rusts it's not his issue, but you may call him with adhesion issues. Then again, I hear he's a real straight shooter.

  7. #7

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    So it really sounds like I need to blast the metal to get into the small pits bc the chemical can only do so much and the wire wheel/DA treatment does not get into the pits. I have noticed that once the rust is removed the metal cleans up very nicely with a DA. But with the DA alone it takes forever to do one small area. Not a valid option.

  8. #8
    autobodytech43 Guest

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    no, the chemical does get into the pits. It does what your sander can't do. What people worry about is human error and people not fully neutralizing the conditioner. I'm sure Barry can tell you horror stories but others will tell you the opposite. When using a conditioner you gotta neutralize it fully and then blow it dry quickly.

  9. #9
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    Quote Originally Posted by merbesfield View Post
    So it really sounds like I need to blast the metal to get into the small pits bc the chemical can only do so much and the wire wheel/DA treatment does not get into the pits. I have noticed that once the rust is removed the metal cleans up very nicely with a DA. But with the DA alone it takes forever to do one small area. Not a valid option.
    The reason Barry doesn't want you to use a rust converter is because his epoxy primer has ACID in it and will peel off the surface. If you purchase a good epoxy prime with no acid then using a good rust converter on the metal will work fine. We do it all the time but if the primer has acid in it you can be sure it's going to peel.

  10. #10
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    Picklex does not get neutralized or rinsed.

    It is not compatible with SPI epoxy because it has acid in it.

    Picklex is compatible with KIRKER ENDURO EPOXY PRIMER. No induction time either.
    [SIGPIC]

  11. #11
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    We deal with this type of rust all the time and usually they need sandblasted but from what I see in your pics we would get rid of areas like whats on the fender in front of the door in pic #1 with a wire brush or a cup brush and then spray it with PPG's CRE(we use alot of that), but then we have to topcoat the CRE within a day or 2 or else it needs sanded first which can be a chore. We do this alot and don't have problems with rust coming back through, but then again we're working on International snow plow trucks with salt spreader tailgates. The only thing better that I know of would be zinc coating but I have no experience with it. Good luck.

  12. #12

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    Quote Originally Posted by Len View Post
    The reason Barry doesn't want you to use a rust converter is because his epoxy primer has ACID in it and will peel off the surface. If you purchase a good epoxy prime with no acid then using a good rust converter on the metal will work fine. We do it all the time but if the primer has acid in it you can be sure it's going to peel.
    Len, that is exactly the problem. So SPI Epoxy has ACID and others do not. Isn't Picklex20 similar to PPG metal prep? I remember using some stuff a long time ago that was a green liquid and it sort of etched the metal before I applied paint. Worked well. So what brands of Epoxy primer is recommended that is compatible with a rust converter?

    The bigger question is what to do with the rust that is under the fenders in the inner fenders. I know that when I media blast metal it is clean, zero rust, I can see it. I am concerned that leaving it and relying on a chemical to convert the rust will not work and I feel like I am doing a half as$^&%&%ed job? True or not, that is what I feel like having no experience with Picklex20. Here is a pic of the inner fender of the 356. After removing all the factory undercoating the metal is super solid, but there is of course the surface pitting that was caused from years of moisture getting under the undercoating. If I sand blast, the media will get all inside the car, and that will be a big issue. This car is not stripped and on a rotisserie. This is sort of a rolling restoration if you will. But I also do not want to do a half way job. I have wire wheeled as much as possible, but it is impossible to get to all the areas, hence the media blasting.
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  13. #13
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    Quote Originally Posted by merbesfield View Post
    Len, that is exactly the problem. So SPI Epoxy has ACID and others do not. Isn't Picklex20 similar to PPG metal prep? I remember using some stuff a long time ago that was a green liquid and it sort of etched the metal before I applied paint. Worked well. So what brands of Epoxy primer is recommended that is compatible with a rust converter?

    The bigger question is what to do with the rust that is under the fenders in the inner fenders. I know that when I media blast metal it is clean, zero rust, I can see it. I am concerned that leaving it and relying on a chemical to convert the rust will not work and I feel like I am doing a half as$^&%&%ed job? True or not, that is what I feel like having no experience with Picklex20. Here is a pic of the inner fender of the 356. After removing all the factory undercoating the metal is super solid, but there is of course the surface pitting that was caused from years of moisture getting under the undercoating. If I sand blast, the media will get all inside the car, and that will be a big issue. This car is not stripped and on a rotisserie. This is sort of a rolling restoration if you will. But I also do not want to do a half way job. I have wire wheeled as much as possible, but it is impossible to get to all the areas, hence the media blasting.
    Blasting is the ultimate rust remover but if you don't have the equipment or ability to blast off the rust without damaging the metal then Picklex is the best alternative we've found. After removing the loose rust you spray or brush Picklex on then work it in with a scuff pad then wipe off the excess and allow it to dry. Scuff the treated surface prior to applying Zero Rust or acid free epoxy primer.

  14. #14

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    Who sells Black acid free epoxy primer? Is DP40 acid free? Thanks

  15. #15
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    Quote Originally Posted by merbesfield View Post
    Who sells Black acid free epoxy primer? Is DP40 acid free? Thanks
    When I need black epoxy primer I use RM EP769, it works well over treated metal.

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