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Gloss white painted lid turning yellow above flow coated box inside

Discussion in 'Tech Tips and Advice' started by Colin Ives, Apr 3, 2016.

  1. Colin Ives

    Colin Ives New Member

    Hi there,

    I have a new product that involved polyester flow-coating the inside of a box and then having a lid that I paint with white gloss but within a couple of weeks areas of gloss facing the inside turn yellow! Is residual styrene or something else attacking the paint surface or is there something else going on? Is there a gloss paint that won't react in this way?

    Thanks
    Colin
  2. Martin @ EC Tech

    Martin @ EC Tech Tech Staff Member

    Hi Colin, unfortunately this is not something we have came across before. I know that Styrene can attack household gloss paints and acrylics such as car paints.

    If painting GRP I usually recommend leaving the GRP for a good few months or even post curing which involves baking it at so many hours at least at 40Deg C depending on the type of resin ect used. you may be restricted on post curing temp for GRP parts made with general purpose resin due to risk of warping.

    Generally if you paint over fresh GRP or flowcoat too soon it tends to cause blistering rather than discoloring to the paint, although I wouldn't rule it out as a cause. If painting over flowcoat or GRP I would also recommend a 2 pack marine paint and suitable primer both of which can usually be found at most chandler's and are more UV stable than gloss.

    Meanwhile I have e-mailed one of the chemists at our suppliers to see if they know more on this and I will be in touch. Kind rgds Martin
  3. Colin Ives

    Colin Ives New Member

    Hi, Martin & thanks for your reply. The yellowing isn't where I've painted over the flow coat, just on surfaces on painted wood that face into it. I've been reading up a bit more about yellowing white gloss and its something that happens normally with modern oil-based modern paints but the process seems to have accelerated on closed surfaces that face the flow coat. Maybe I( need to find a non-oil-based gloss paint?

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