Underseal
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Thread: Underseal

  1. #1
    Member DSuper's Avatar
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    Default Underseal

    Hi,

    I've previously posted about the paint job on my D Super chassis frame. I had painted it myself along with some bad advice and the result was the (wrong) paint did not stick to the metal.

    Wanting to get the thing finished in a tight timeframe, and really busy at work, the paint supplier recommended a painter (all in one paint and panel shop, lifetime warrenty etc.) who was going to strip (sandblast) all the previous paint and repaint with epoxy. I popped in the other day and they were about to apply underseal to my previous not suitable porus paint job now with some bare metal - where the blaster had hit it in some places (excuse: the blaster didn't want to remove the wheels) (all the most vulnerable parts - wheel arches and lower vertical parts on the sills were still in my bad paint job and now part bare metal - 'ready for' underseal.

    I'm volunteering to go in Monday to strip it myself by hand so that they can epoxy it as agreed. (paying someone and still doing it myself!)

    The underseal instructions seem to indicate its OK to underseal straight on bare metal. A paint retailers advice was epoxy primer then underseal.

    Question: Is epoxy then underseal OK or do I tell the painter to forget about the underseal and epoxy prime, then do one or two top coats (and then I'll underseal it myself later) (his masking out for underseal was a bit sloppy too - not per my diagrams)

    Cheers for any advice,
    Ben.

    EDIT: Changed "The paintshop advice is epoxy primer then underseal" to "A paint retailers advice was epoxy primer then underseal"

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    Last edited by DSuper; 20th November 2011 at 12:16 PM.

  2. #2
    Real cars have hydraulics DoubleChevron's Avatar
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    Go with the painter. Epoxy is probably the best primer there is. However there is a re-coat window. Some epoxy coatings will need to be sanded (keyed), re-coated with epoxy then have the top coats applied if not re-coated in the re-coat time frame (it could be hours or days/weeks depending on the products spec sheet).

    I'd be getting it all down at once so you don't have to worry about it in the future. There's no way I'd be putting underseal straight onto bare metal if you have the opportunity to seal it all off with epoxy!

    To get an idea of how highly epoxy primers are thought of, go and have a read around here about primers:

    http://www.autobody101.com/forums/viewforum.php?f=5

    You would be mad not to epoxy after all the effort of stripping/blasting etc...

    seeya,
    Shane L.
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  3. #3
    JBN
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    I gues the expoxy is probably POR15. I would coat all sandblasted bare metal with this. It works best with the rough sandblasted surface. Any cleaning agent for POR15 preparation is alkaline, not thinners as with most automotive paints and underseals.

    POR15 is very black and glossy first up, but dulls over time depending upon the UV content hitting it. It is NOT UV stable from a colour/gloss point of view, but ideal for chassis.

    I would do the underseal later yourself. A bit of aging of the POR15 will help in adhesion. Then you know it has been done properly and you also know that the paint shop has done their job.

    John

  4. #4
    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by JBN View Post
    I gues the expoxy is probably POR15. I would coat all sandblasted bare metal with this. It works best with the rough sandblasted surface. Any cleaning agent for POR15 preparation is alkaline, not thinners as with most automotive paints and underseals.

    POR15 is very black and glossy first up, but dulls over time depending upon the UV content hitting it. It is NOT UV stable from a colour/gloss point of view, but ideal for chassis.

    I would do the underseal later yourself. A bit of aging of the POR15 will help in adhesion. Then you know it has been done properly and you also know that the paint shop has done their job.

    John
    Por 15 is not epoxy.

    Jo

  5. #5
    Member DSuper's Avatar
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    The aim/ agreement with the painter/ my understanding! was: Sandblast all my (crappy job) previously painted areas. Epoxy prime, seam seal and paint all. Underseal certain areas. It seems to me the blaster and the painter were being a bit slack and not stripping properly and epoxy priming the areas under the underseal.

    New plan: I now have to strip these (unblasted & to be undersealed) areas by hand and epoxy prime before underseal. (as agreed) (I can't be bothered argueing that they take it back to the blaster at their cost)

    To state the question more clearly: Is it best, or just unneccesary to apply topcoats over the epoxy primer, before underseal? Is metal, then epoxy primer, (no topcoats) then underseal good long term protection?

    Cheers.

    P.S. Shane, I took on (your) advice about epoxy and this was my new objective, but the slack attitude of the painter meant this objective was not being met! If the underseal lifts then there is no 2nd layer of protection. ie. Epoxy. Hence my now handstripping large areas the blaster missed. (to then be epoxy primered, then...?, then underseal)
    Last edited by DSuper; 20th November 2011 at 12:19 PM.

  6. #6
    Real cars have hydraulics DoubleChevron's Avatar
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    You need to get the spec sheets on the epoxy and see how and when you can apply any coatings over the top Certainly I'd be using it over a coating like POR15 every single time. If it was something really difficult to strip to clean rust free metal (eg: the inner wheel arches around all the hydraulic pipes) I'd be tempted to clean, wire brush/POR15. Simply on the basis it's better than nothing I think POR is quite good and have used it a bit over the years, but I'd wouldn't dream of using it where you can do a proper job with high quality primers & top coats !

    seeya,
    Shane L.
    'Cit' homepage:
    Citroen Workshop
    Proper cars--
    '85 Series II CX2500 GTi Turbo I
    '63 ID19 http://www.aussiefrogs.com/forum/showthread.php?t=90325
    '72 DS21 ie 5spd pallas (last looked at ... about 15years ago)
    '78 GS1220 pallas
    '92 Range Rover Classic ... 5spd manual.

    Yay ... No Slugomatics


    Modern Junk:
    '07 Poogoe 407 HDi 6spd manual

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