Epoxy drying time before painting - non--xposed surfaces

[avole]

Another question from a nervous first-time builder.

I epoxied the interior sections of the bouyancy tanks on my sailing dinghy yesterday. These are areas that will be sealed during sailing and the only access is through inspection hatches and small bungs to provide drainage. I want to paint the interiors white now so it's easier to see if there's any water within following a tip or similar.

Now, I had planned to leave then 48 hours before painting but now I see the wait time is a week. Assuming the epoxy is ready to clean and sand tomorrow, I take it, if I paint afterwards, there'll be no ill effect? The surfaces will never be exposed except for inspection, so quality of finish isn't a concern.

The seat tops and sides, and the decking from the main bulkhead to the bow form the exterior of the tanks - pictures of the type of dinghy at www.125assoc.com.

The reason I ask is I took a week off to get the hull completed and ready for the sanding stage, and this won't be achievable if I wait the recommended time. I'd allocated 48 hours.

[Bert Langley]

You might get away with it. Are you using non-blushing epoxy? How warm is it where you are building? What paint are you expecting to use?
Anytime you go against the manufacturer's recommendations you run the risk of it not working. However, what is the downside if the paint does not adhere? Worst case is you have a mess in the tank and it will be a real PIA to clean and redo through the inspection hatches. Not a killer by any means but something to consider.

I might consider adding a tint to the epoxy, putting on another coat and calling it good.

[RodB]

If the inside surface of these flotation tanks has been properly coated with epoxy why not just apply another coat of epoxy (As Bert suggests) with white pigment in it... it will look shiny and slick and increase your moisture barrier on the inside surface... especially on the bottom where water will stand if any gets in.... With closed compartments, its a waste of time to paint them... and paint will not provide the barrier plain epoxy will. I have used epoxy tinted white on the inside of several compartments on boat repairs where the inside shows when the compartment is opened... they look good and are very tough. Paint is required when an epoxy surface will be exposed to UV light or to just make the surface look better. I wouldn't want paint where water may stand. White tinted epoxy would be a much better choice and you really only have to coat the bottom of the tank with tinted epoxy.

If you are determined to paint the inside surfaces.... and its been 2-3 days in warm temps... just clean them up with scotchbright and warm water (knock off the shiney)... wipe clean... make sure surface is clean and no blush exists and shiney is removed from surfaces ... then simply add Cobalt Drier (available from any art store) to your paint (6 drops per ounce of paint) and the paint will dry no problem whether free amines are still coming off the curing epoxy or not.

RodB

[switters]

the epoxy will still cook off for a week and if you paint you may, not always but may, get some bubbling of the paint. If you don't care what it looks like then it is your call, the epoxy cure will not be affected.

When you do care, as I have in the past, and not waited the whole week, then you will get bubbling in the paint. I know this, it is a corollary to Murphy's law.

[RodB]

I have painted atop 2-4 day old epoxy (system three) many times and have never seen any bubbling... Free amines continue for many weeks to some degree.... In my experience, a clean scotch-brighted surface painted with paint that had colbalt drier added dried fine within a few hours... no bubbles...ever. In this situation, usually the epoxy is quite firm... cured for a couple days... once you wash off the amine blush... the surface is clean and toothed... and you can paint right on top of it with added drier to compensate for the driers in the paint being affected by the free amines coming off the epoxy.

RodB