Bear with me as I describe the time-line of my 11 year slow motion paint failure which I feel was caused by UV penetration/degradation of the epoxy primer underneath:
2007:
- Bought my 1980 boat. (27 years ex-yard then. 38 years old now.)
- The white gelcoat on the cabin top was total chalk. A rub down with just a dry terry cloth towel in some areas revealed the underlying layer of actual fiberglass mat layup.
- Power sanded all down to a firm paintable surface.
- My choice was to renew the surface with a major manufacture's marine 2-part polyurethane. (Will not divulge the manufacturer here.)
- Followed instructions exactly.
- First step was to apply a 2-part epoxy primer coat. (But I do recall debating whether this was necessary or if I should simply apply the finish coat.) Even though I followed exactly the instructions as to the ratio of the manufacturer's $25 a pint thinner, and I applied in cool weather, brush marks did not "wet" out. The epoxy primer set rock hard. So lots of sanding to rectify. Eventually good to go. The hardened primer was almost pure white.
- Then applied two coats of the 2-part polyurethane. One of the manufacture's "white" colors. Also mixed in some flattening agent since I didn't want super high gloss. Did not exceed the max allowed ratio of paint to flattening agent.
- Job not perfect but still I was quite pleased with the result. And several years on, the surface of the 2-part polyurethane had not degraded at all. Just as advertised!
2011-2012
- I started to notice that in certain areas of my paint job, the color was turning from white to a sort of tan. Chipping away a bit at those locations, the 2-part surface paint separated easily from the underlying epoxy primer. The surface paint chips were still white. But the underlying primer no longer was.
- Trying to analyze, I recalled reading that epoxy degrades with UV exposure. Maybe two coats of white 2-part polyurethane mixed with the flattening agent wasn't enough to block UV penetration onto the epoxy primer? And the primer itself was degrading as a result?
- I called the manufacturer for advice. Just got a vague "strange" and "don't know" type of response.
2013
- Even though the 2-part polyurethane surface was still looking much like the day I applied it, I decided to put another couple of coats to thicken the layer and hopefully prevent further UV penetration to the underlying primer.
- I didn't machine grind/sand everything down to virgin FRP. But over a couple of weeks, hand-sanded the hell out of the surface. Again followed the manufacturer's recommendations as to surface prep and application. Since the surface was now smooth and solid, I did not need to pre-coat with primer again.
- All looked good. Again, the 2-part paint surface does hold up splendidly over the years.
2016-2017
- Every so often and in just a few small sections, the 2-part polyurethane would simply peel away from the now tan epoxy primer. Particularly if lightly impacted with something dropped.
2018
- Had been since 2013 that I painted my port surrounds. Were looking a bit tired.
- On a recent the afternoon, applied blue 3-M masking tape over the cabin top 2-part polyurethane.
- Painted the surrounds the next morning.
- Removed the masking tape right after.
- Look at the attached photo! The 2-part has almost totally separated from the underlying primer!
- The once white epoxy primer is totally yellow/tan. And I can even put a gouge in it with a fingernail. No longer rock hard!
My solution going forward: Old boat. Plus less finicky and getting older owner. Don't want to deal with grinding/sanding down the surface to remove everything. (Which in California anyway shouldn't be done at the berth due to water contamination concerns.) I will simply whimp-out and dab on white 1-part polyurethane wherever paint separation happens.
The other photo is the appearance of my deck and cabin top during happier days gone by.
Anyone else have UV failure stories?
2007:
- Bought my 1980 boat. (27 years ex-yard then. 38 years old now.)
- The white gelcoat on the cabin top was total chalk. A rub down with just a dry terry cloth towel in some areas revealed the underlying layer of actual fiberglass mat layup.
- Power sanded all down to a firm paintable surface.
- My choice was to renew the surface with a major manufacture's marine 2-part polyurethane. (Will not divulge the manufacturer here.)
- Followed instructions exactly.
- First step was to apply a 2-part epoxy primer coat. (But I do recall debating whether this was necessary or if I should simply apply the finish coat.) Even though I followed exactly the instructions as to the ratio of the manufacturer's $25 a pint thinner, and I applied in cool weather, brush marks did not "wet" out. The epoxy primer set rock hard. So lots of sanding to rectify. Eventually good to go. The hardened primer was almost pure white.
- Then applied two coats of the 2-part polyurethane. One of the manufacture's "white" colors. Also mixed in some flattening agent since I didn't want super high gloss. Did not exceed the max allowed ratio of paint to flattening agent.
- Job not perfect but still I was quite pleased with the result. And several years on, the surface of the 2-part polyurethane had not degraded at all. Just as advertised!
2011-2012
- I started to notice that in certain areas of my paint job, the color was turning from white to a sort of tan. Chipping away a bit at those locations, the 2-part surface paint separated easily from the underlying epoxy primer. The surface paint chips were still white. But the underlying primer no longer was.
- Trying to analyze, I recalled reading that epoxy degrades with UV exposure. Maybe two coats of white 2-part polyurethane mixed with the flattening agent wasn't enough to block UV penetration onto the epoxy primer? And the primer itself was degrading as a result?
- I called the manufacturer for advice. Just got a vague "strange" and "don't know" type of response.
2013
- Even though the 2-part polyurethane surface was still looking much like the day I applied it, I decided to put another couple of coats to thicken the layer and hopefully prevent further UV penetration to the underlying primer.
- I didn't machine grind/sand everything down to virgin FRP. But over a couple of weeks, hand-sanded the hell out of the surface. Again followed the manufacturer's recommendations as to surface prep and application. Since the surface was now smooth and solid, I did not need to pre-coat with primer again.
- All looked good. Again, the 2-part paint surface does hold up splendidly over the years.
2016-2017
- Every so often and in just a few small sections, the 2-part polyurethane would simply peel away from the now tan epoxy primer. Particularly if lightly impacted with something dropped.
2018
- Had been since 2013 that I painted my port surrounds. Were looking a bit tired.
- On a recent the afternoon, applied blue 3-M masking tape over the cabin top 2-part polyurethane.
- Painted the surrounds the next morning.
- Removed the masking tape right after.
- Look at the attached photo! The 2-part has almost totally separated from the underlying primer!
- The once white epoxy primer is totally yellow/tan. And I can even put a gouge in it with a fingernail. No longer rock hard!
My solution going forward: Old boat. Plus less finicky and getting older owner. Don't want to deal with grinding/sanding down the surface to remove everything. (Which in California anyway shouldn't be done at the berth due to water contamination concerns.) I will simply whimp-out and dab on white 1-part polyurethane wherever paint separation happens.
The other photo is the appearance of my deck and cabin top during happier days gone by.
Anyone else have UV failure stories?
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