over coating coal tar epoxy

Discussion in 'Materials' started by owensp, May 30, 2012.

  1. owensp
    Joined: Oct 2010
    Posts: 9
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    Location: Ireland

    owensp Junior Member

    Dear forum,

    i have put a layer of coal tar epoxy on the inside of the bow area of a steel bruce roberts mauritius. I had the coal tar left over from repairs i was doing on the hull and thought i should use it up before the paint goes off (shelf life 1 year only). The colour is brown - I need to end up with something lighter in colour . Has anyone got experience of overcoating this with single pack ? Will it work ok or do i need to get another 2 pack for this? any suggestions?


    Peter Owens
  2. Frosty

    Frosty Previous Member

    Re coating another undercoat type of paint should have been done withing 24 hours or while the coat tar would make a molecular bond. If its gone off for a few days it is a shiny surface and I think you will have difficulty painting on top of it. It is not meant to be used that way --it is a protective coating I use it a lot.

    Its ideal for under boat protection grind down a coat of zinc primer--coal tar and anti foul almost as its air dry. the antifoul will/ should bleed through that is good. Add another few coats of antifopuling on top of that.

    I had a Roberts Mauricious.
  3. mastcolin
    Joined: Jun 2005
    Posts: 151
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    Location: The Netherlands

    mastcolin Senior Member

    It will all depend on the coal tar. They are not all the same.

    It will probably bleed into the topcoat overtime. ie it will go dirty yellow. Adhesion may be problem longterm.

    Speak with International Paint. I seem to remember that they used to have a sealer for coal tar.

    ps ignore the shelf life. In most cases it makes no difference. Shelf lifes were in the main driven by consumer good market. So many products now get a "shelf life" which only means that the product still meets the specification that it was sold at (to do with ISO900 regulations on quality). Outwith this time it may not meet its specification but will almost all of the time, do the same job. It may dry slower, it may be stickier to brush for example. It will do what it says on the tin otherwise.
    Last edited: May 31, 2012

  4. pauloman
    Joined: Jun 2010
    Posts: 268
    Likes: 10, Points: 18, Legacy Rep: 151
    Location: New Hampshire

    pauloman Epoxy Vendor

    generally you cannot topcoat coal tar epoxy, especially if it is weathered. Weathering releases the 'tar' and nothing sticks. It is perhaps one of the main disadvantages of coal tar epoxies (plus data that coal tar can cause cancer) and the reason why coal tar epoxies are less and less common.

    I have commercially been selling coal tar epoxy for the past 12 years and have personal customer feedback both good and bad.

    paul - progressive epoxy polymers inc
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