Where did I go wrong?

Hoping to get some advice on something that didn't work out for me.
I've been repairing a fibreglass kayak which had split. I epoxied the top and bottom halves back together, then run some new tape around the entire seam. It was then sanded and waiting for flow coat/2 pac. At this point, life and personal issues got in the way, and it sat untouched for 12-18 months. I recently thought about getting it finished, but was concerned that maybe the new tape around the seam was insufficient. I masked up and ran another layer of tape along one side, wet it out and applied the subsequent fill coats. This afternoon I went to remove the masking tape, and as I was pulling it off, I noticed a small section of the new tape seemed to lift as well. I grabbed a scraper and probed at it and it quite easily started to lift off. Once I could get a finger hold, the entire length peeled off like masking tape, with very little effort.
Attachment 395972
The tape underneath had been sanded (prior to sitting for 12-18 months) and cleaned down with acetone prior to the last layer of tape going on.
Any ideas as to what went wrong, and what I can do to remedy the situation, as I'd really like to get another layer of tape on the seam.
Thanks,
Chris

I sounds like amine blush existed and though you sanded (smearing it into the surface) the acetone wipe, doesn't remove it. Amine is water soluble, so a simple scrub with a scouring pad and a few drops of dish detergent in a bucket of water is all that's necessary. Surface contamination, plain and simple. It happens to the best of us. Pull what remains of the tape, scrub the surface good with warm water and a little soap. After this is dry, sand in prep for another layer of tape. Don't use fine grit paper, 100 is about as fine as I'd go, but I prefer a good mechanical "keying", so my usual choice is 40 - 60 grit, to lay down big 'ol scratches, the goo and fabric have to get a good grip on.

Thanks PAR,
I'm using Bote Coat, so amine blush shouldn't be an issue. The grade of the sanding could have been part of the problem. It would have been down to 240/320.
Would the fact that it sat for 12-18 months be an issue? It was stored under cover, and would have been exposed to normal daylight, but not direct sunlight. If that's an issue, would sanding back with say 60 grit be ok?

Yeah, those grits are way too fine for a good mechanical "keying" of subsequent coatings. It's not a two pack LPU, just epoxy.

Even epoxy formulations are are supposed to be blush free, often can blush anyway. It's all about environmental condisions, temperature and humidity mostly. The unreacted amines on the surface are affected by moisture (and other stuff) in the air and can leave a waxy film, once cured, which we call blush. Humid days will cause the worst of it, but something as simple as a open flame, can put enough partly spend hydrocarbons into the air to cause a reaction. My usual recommendation is unless you can really control the environment (HVAC), you should just figure you'll have some level of blush on the surface, that needs to be washed off.

Reflected UV can still damage epoxy, that's not protected. It takes a lot longer and the epoxy color is the usual "tell". If it's very yellow or hinting at brown, you have UV damaged epoxy.

It sounds like a combination of things conspired to you off. Unfortunately, I think you know what needs to be done.

Quote:

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Originally Posted by PAR

Unfortunately, I think you know what needs to be done.

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Bugger.
Thanks for your help PAR.