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Hot Rods should I use copper or zinc weld Tru primer?

Discussion in 'The Hokey Ass Message Board' started by old_chevy, Jul 6, 2020.

  1. old_chevy
    Joined: May 28, 2012
    Posts: 69

    old_chevy
    Member
    from USA

    trying to decide what primer to use for autobody spot weld and plug welds
     
  2. 62SY4
    Joined: Oct 30, 2009
    Posts: 86

    62SY4
    Member
    from Irwin, Pa

    This is a popcorn thread ...

    When I use it, I use zinc because that's what all the local jobbers carry. Some people claim splatter issues with it, others claim it is toxic. Ideally you want nothing to contaminate your weld pool, but you are probably using copper coated mig wire so that quickly goes out the window.

    If you believe it works, I'd say use zinc because it is less noble than iron so it becomes sacrificial. Copper is more noble than iron so no benefit there.
     
  3. Pats55
    Joined: Apr 29, 2013
    Posts: 416

    Pats55
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    from NJ

  4. Lloyd's paint & glass
    Joined: Nov 16, 2019
    Posts: 2,767

    Lloyd's paint & glass
    ALLIANCE MEMBER

    I use zinc. And don't go crazy heavy, i just put enough to cover. And let it dry good before you try to weld. Heavy coats and not being dry is the reason for spatter. That's my experience.
     

  5. 66gmc
    Joined: Dec 4, 2005
    Posts: 566

    66gmc
    Member

    Copper seems to have become the norm in the collision industry, and all those fancy spot weld machines seem to recommend using copper. That being said I've cut apart a few cars that had copper weld thru, and the seams were rusting.
    At home I use zinc and have had no issues. I think the key is putting it on in a light coat, and clamping the 2 layers of metal around each weld tightly. If your having trouble with spatter or put it on too thick you can take a small screwdriver and scrape the weld thru off inside of each hole before welding.
    Weld thru primer is meant as a sacrificial coating for when 2 or more layers of metal are flanged or overlapped together. Ive seen a lot of people spray it on everything, even when butt welding, which is a complete waste of time, not only that but it has almost no adhesion properties, meaning if you start putting other primers or topcoats over it, you may be in for a nasty surprise later on...nothing sticks to weld thru primer, and weld thru primer sticks to nothing.
     
  6. Zinc...ever see what a penny does when ya leave it in a damp environment..
     
  7. bobscogin
    Joined: Feb 8, 2007
    Posts: 1,761

    bobscogin
    Member

    Pennies are 97.5% zinc and 2.5% copper.

    Bob
     
    gimpyshotrods likes this.
  8. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,676

    gimpyshotrods
    ALLIANCE MEMBER

    Yup. If pennies were made of copper, they would cost way more than $0.01 to make.
     
  9. old_chevy
    Joined: May 28, 2012
    Posts: 69

    old_chevy
    Member
    from USA

    I just got some of the upol weld Tru copper primer. I also have the 3m weld Tru primer. I'll test them both out and see what works best.
     
  10. larry k
    Joined: Feb 23, 2009
    Posts: 320

    larry k
    Member

    It always makes my welds act as if something is on the metal??? Because well something is on the metal .!!!!!!!!!!!!!
     
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  11. Luke stone
    Joined: Sep 5, 2017
    Posts: 118

    Luke stone
    Member

    I use zinc as that’s what I was given when I started welding. I do however run a spot weld drill in the hole before I plug weld so really I just use it so there is something between the panels
     
    Gasser 57, Bugguts and RMR&C like this.
  12. Amazes me how many people contaminate their welds with this stuff because they don't know how to use it!
     
  13. gene-koning
    Joined: Oct 28, 2016
    Posts: 2,037

    gene-koning
    Member

    I used 1 can of the zinc 25 years ago, haven't used it since. Give me clean dry steel. I'll seam seal the weld. Unless you plan on running the weld seam under water, it will last a very long time, I haven't had a rust issue yet. Gene
     
    b-body-bob, MMM1693 and Fortunateson like this.
  14. Fortunateson
    Joined: Apr 30, 2012
    Posts: 3,426

    Fortunateson
    Member

    I'm starting to feel the same way.
     
    b-body-bob likes this.
  15. big duece
    Joined: Jul 28, 2008
    Posts: 6,024

    big duece
    Member
    from kansas

    They were 95% copper up until 1982...
     
  16. big duece
    Joined: Jul 28, 2008
    Posts: 6,024

    big duece
    Member
    from kansas

    31E4CVFA6tL.jpg
    I have had good luck with this product...
     
  17. old_chevy
    Joined: May 28, 2012
    Posts: 69

    old_chevy
    Member
    from USA

    I've been testing the upol weld Tru copper primer. I clean the metal, use a de-greaser and the two coats of the weld thru primer. I'm using a miller spot welder 220v 30amp. I'm getting burn thru on the spot welds. I never had that happen before.
     
  18. old_chevy
    Joined: May 28, 2012
    Posts: 69

    old_chevy
    Member
    from USA

    when you spray the weld Tru primer on do you lightly dust it so that some bare metal is still exposed?

    I put two coats on but im thinking it was too much. im going to try one coat
     
  19. Lloyd's paint & glass
    Joined: Nov 16, 2019
    Posts: 2,767

    Lloyd's paint & glass
    ALLIANCE MEMBER

    Kinda, i don't go heavy on the area where I'm welding.
     
  20. FWIW, Toyota and Chrysler say not to use it. They want you to treat the seam after assembly.
     
  21. old_chevy
    Joined: May 28, 2012
    Posts: 69

    old_chevy
    Member
    from USA

    another option is panel adhesive and using spot welds
     
  22. anthony myrick
    Joined: Sep 4, 2009
    Posts: 6,199

    anthony myrick
    Member

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