Epoxy primer before or after bondo??

Discussion in 'Body Restoration' started by NYH1, May 14, 2010.

  1. NYH1

    NYH1 Veteran Member

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    Feb 27, 2010
    Central New York
    I had to weld some patches on the lower parts of my front fenders. Should I put epoxy primer on them before or after I put bondo on them?

    Thanks.
     
  2. Blu-By-U 79Z

    Blu-By-U 79Z Veteran Member Lifetime Gold Member

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    Feb 11, 2009
    Kentucky
    i say after. Because filler is supposed to be on baremetal. You can put filler over epoxy but you run the chance that it wont bond.
     
  3. BusDriver

    BusDriver Veteran Member

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    Apr 28, 2004
    Charlotte, NC
    Both. Seal the metal up, do the filler then use it as a sealer before basecoat.

    Filler is porus and water will infuse it if given the chance, I dont want that next to the metal. Paranoid, maybe, but it makes me warm and fuzzy to know the metal is entombed and SEALED.

    Scuff the epoxy well if adhesion is a concern.
     
  4. leafs_11

    leafs_11 BANNED

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    Jun 24, 2009
    i had a lenghthy phone chat with the company rep from pro form.
    bondo over metal can stick better but also chance it could let go.better to seal with epoxy first . it makes sense.sand blast or wire brush your welds real good.blow off dust and tack cloth. thats just common sense.
    he also said to let the epoxy cure for 24 hours before applying bondo.
    wenever i welded my patches i used a bright light to make sure all the pinholes were filled with weld.that way its sealed from backside.
    im no body man or xpert im just extremely fussy.
    all my patches i did required minmal bondo as my welds did all the work.
    a die grinder will be your best friend.
    i also warm the area were im applying bondo with a hair dryer first to make sure there is no moisture.
    wen i sand bondo i reapply epoxy to any bare metal that i break through.
     
  5. mscamp02

    mscamp02 Veteran Member Lifetime Gold Member

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    Jan 25, 2010
    Mt Sterling, Ky
    wookie and SPI told me to use epoxy then bondo then epoxy then high build 2k before laying down base. So thats what Ill do
     
  6. wookie

    wookie Veteran Member Lifetime Gold Member

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    Jul 12, 2006
    Daytona Florida
    Yep.
     
  7. Blu-By-U 79Z

    Blu-By-U 79Z Veteran Member Lifetime Gold Member

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    Feb 11, 2009
    Kentucky
    The autobody instructor at the college was the one who said to work the filler then epoxy because hes seen the filler not bond well to the surface over epoxy and pop off shortly down the road. Fillers designed to go on metal. Same reason you dont want it over paint. It just doesnt bond good enough. Now if its a small dent. Epoxy and use a glasze puddy. That is fine to put over primer.
     
  8. wookie

    wookie Veteran Member Lifetime Gold Member

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    Jul 12, 2006
    Daytona Florida
    I hate to question the instructor at your local college but this is erroneous information in 90% of cases. The newer epoxies like SPI are designed to take filler and have excellent adhesion properties. Filler on the other hand does not tend to adhere as well to metal as it does epoxy.

    At least in the 20+ years I've been doing this that was the case...Maybe he knows something I don't?
     
  9. Blu-By-U 79Z

    Blu-By-U 79Z Veteran Member Lifetime Gold Member

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    Feb 11, 2009
    Kentucky
    Hes been doing auto body for over 30 years. Ive been doing it this way with no issues. Just prepwork regardless. We dont use SPI. We use PPG Epoxy primers. So idk if that is one in the same but i dont belive so. It could depend on what type of material you are using.
     
  10. JR454

    JR454 Veteran Member

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    Jul 25, 2005
    Indiana
    got to agree- The best is to spray epoxy before and after filler.. Been doing it that way for many years on restorations. Im using ppg- and The tech guys at the ppg center actually said that the filler bites better to the epoxy than bare metal. I agree with wookie- I think most all of the paint manufacturers epoxy is designed to have filler over it.
     
    Last edited: May 14, 2010

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