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Thread: Under body painting.

  1. #1
    Join Date
    Aug 2013
    Location
    Boring Oregon
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    Default Under body painting.

    ick
    I have patched and sealed a couple patches in the floor.

    Now the bottom of the car is the bottom of a 50 year old car. It's dirty/oily.

    I rough sanded things down a bit around all the sealed patches and I'm getting ready to seal it up.

    No matter how many times I wipe, there is some residue from that original factory undercoating.

    My questions:
    Should i spray the zero rust onto the undersurface first, then apply duplicolor rubberized undercoat after wards to blend the texture.
    OR should I spray the rubberized undercoat first since it (may/may not) stick to a less than perfect surface and then even it all out with zero rust?
    Adhesion Promoters such as SEM77723, will this help, hurt or do nothing?

    As it is, I'm scrubbing with industrial purple. wiping with parts cleaner and then using pre-paint prep/ W&G remover prior to covering.
    There are blobs of original undercoating that are still there.
    I have zero intention of smoothing out the bottom of a street ride. Under the drivers feet isn't important to me.

  2. #2
    Join Date
    Dec 2015
    Posts
    1,136

    Default

    If I understand this correctly you had a few places where your floor pans rusted through and you created and installed new sheet metal patch panels correct? My typical underside pan repair on 50's and 60's model cars for floor patch panels that have a rubberized coating would look something like this; mark and cut out rusted area in question that extents to solid sheet metal, using a combination of die grinders, wire wheels, chemicals, torch, etc., remove all previous coatings down to bare and solid sheet metal that extends 4-6" beyond cut out area. Cut and weld in new patch panel, clean underside with G&W remover, hit with por 15 metal prep and rinse with water after 15-30 minutes, apply 3 coats of Zero Rust, wait 24-48 hours and scratch surface with 180g, apply rubberized coating (I use Lizard Skin). I understand working on underside of pans is not easy but I hate rust, did I mention I hate rust? I just don't want a repair to come back and haunt me. I've done countless floor pan patch panels where the underside is covered in oil, grease, grime, rubberized insulation etc. and know they are no fun. Len put me onto the Zero Rust a few years back and it has been my go to product ever since, I really love it. On the residue you are experiencing during the cleaning stage, try wiping the panel in one direction from the clean side out. The metal prep for laying your Zero Rust will will aid in stabilizing contamination as it leaves a phosphate surface but adhesion may be hampered if it is anything other than residue. Your adhesion promoter will do nothing for this repair. A photo would really help to guide you.

  3. #3
    Join Date
    Aug 2013
    Location
    Boring Oregon
    Posts
    4,067

    Default

    OK. Here are some pics.
    First one is looking thru the engine compartment. You can just see some of the fusor sealant from the front.

    IMG_0587.jpg

    Here is under the driver seat. The patch was right up against the floor gas pedal studs. You can see where I spread out the Fuzor, beige, and the floor.

    IMG_0591.jpg

    This is the passenger floor area.
    IMG_0588.jpg

    All of these areas end at or before where the floor goes from being parallel to the floor, to the 45 degree rise up to the firewall.

    So you can see the area I'm working. I have ground, sanded, scrubbed and wiped.
    Once it is all black with zero rust, I will splatter around the undercoat to help hide the patches and make sure everything is waterproof.

    This car will most likely not be driven in the rain.

  4. #4
    Join Date
    Dec 2015
    Posts
    1,136

    Default

    Is there a new sheet metal patch panel under all that Fusion? I just don't understand why so much sealant needed to be applied (over protection maybe?). I am not judging your work, just tying to understand how you installed and sealed the new patch panel. When I install new panels or even an entire one piece floor I typically just run a bead (top and bottom side) over cleaned up and prepped metal, wait a few minutes and level flat with a cut piece of a body filler paddle. Fusion is a great product and works really well. While I think this may very well work, I'm thinking maybe we need to find out if Zero Rust will adhere to that much Fusion. If this were mine I would clean up some of the old rubber insulation a few inches back where the pan goes vertical to trans on drivers side pan. This possible? Hopefully Len will lay in here and school us both.

  5. #5
    Join Date
    Aug 2013
    Location
    Boring Oregon
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    Default

    There is a welded in patch panel behind all that fusor. All that fusor is about 1/8 deep The inside was ground smooth and painted a couple years ago.

    There was weld bubbles, wire sticks etc crap all hanging out below.
    I went in, ground off everything fairly flat but still lumpy. Sanded around the floor area to skuff.
    Cleaned and applied a bead of fusor around the lumpy weld bead and smoothed it over with a little acid brush.

  6. #6
    Join Date
    Nov 2013
    Location
    olympia,wa
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    1,759

    Default

    hmm, i would have approached this a little differently. instead of covering the whole area with fusor, i would have sealed the seams, or seam welded it. then use short strand glass filler to smooth the area.
    since you're beyond that point now, i would probably go right to the zero rust. it shouldn't have adhesion issues to the fusor. i haven't had adhesion issues, but i don't usually cover such a large area. i say usually, but i did actually do it about 3 months ago on my shop truck when sealing the firewall and haven't had any issues yet. i use the 126ez (i think) for seam sealer.
    b marler

  7. #7
    Join Date
    Aug 2013
    Location
    Boring Oregon
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    Default

    It would have been proper to grind off the bottom side when I cut out the old patches, however at the time 4-6 years ago, I didn't even have the front end sheet metal off much less the engine and trans out.

    So I welded in from above, got lot's of contamination from the undercoating from below and bird shit welded, ground until I could see no light shining thru. The underside looked gnarly but I never looked at it till this year.

    When I spread the fuzor sealer over the weld itself, on most of the areas, there was less than 1 inch square in the center, so I just spread it out evenly thinking it would eliminate one edge that might lift.
    Anyway, that is why I did, what I did.

    I do intend on cleaning up that firewall area. The frame rails have a few scratches too so I may end up re-painting those. Have to wash everything down and see how the paint looks. It is probably 4 years old now and never been outside. I think it is dry. If I have to mask things off and re-spray the firewall and frame rails to make everything consistent then I will.

    Getting this underside done means I can install the engine and trans. Once those are in, then I can do wiring & plumbing to make the beast run. Not much plumbing left to do. Just trans modulator, carb fuel line and the fuel pump.
    Slow going, but crawling out from under that car will be one thing I don 't miss.

  8. #8
    Join Date
    Dec 2015
    Posts
    1,136

    Default

    Quote Originally Posted by Houndogforever View Post
    It would have been proper to grind off the bottom side when I cut out the old patches, however at the time 4-6 years ago, I didn't even have the front end sheet metal off much less the engine and trans out.

    So I welded in from above, got lot's of contamination from the undercoating from below and bird shit welded, ground until I could see no light shining thru. The underside looked gnarly but I never looked at it till this year.

    When I spread the fuzor sealer over the weld itself, on most of the areas, there was less than 1 inch square in the center, so I just spread it out evenly thinking it would eliminate one edge that might lift.
    Anyway, that is why I did, what I did.

    I do intend on cleaning up that firewall area. The frame rails have a few scratches too so I may end up re-painting those. Have to wash everything down and see how the paint looks. It is probably 4 years old now and never been outside. I think it is dry. If I have to mask things off and re-spray the firewall and frame rails to make everything consistent then I will.

    Getting this underside done means I can install the engine and trans. Once those are in, then I can do wiring & plumbing to make the beast run. Not much plumbing left to do. Just trans modulator, carb fuel line and the fuel pump.
    Slow going, but crawling out from under that car will be one thing I don 't miss.
    I think at this point I would go with bmarlers suggestion of just applying the Zero rust. I can't imagine moisture getting under the Fuson if ZR were to flake off. That ZR is a really good product and aheres well.

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