Poor paint adhesion on exterior fiberglass door

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Old 11-01-15, 07:11 AM
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Poor paint adhesion on exterior fiberglass door

I've been working on painting my exterior fiberglass door but it seems that the paint adhesion is poor. The door came primed from the factory, so I decided to use my airless sprayer to paint.

First, I lightly sanded with 220 grit, vacuumed, then washed with TSP. I uses Sherwin Williams exterior Resilience, thinned it with Floetrol and water to reach the appropriate consistency for my airless srpayer, and then I sprayed 3 coats. Now, it has been a little chilly here in MN, but my garage temps were always above 45 degrees. I gave at least 6+ hours for each coat to dry.

But, today, while moving the door, I noticed how easily the paint can be scraped off the fiberglass. In fact, if I take my fingernail and press hard enough, I can peel the paint off. That doesn't seem right.

Did I do something wrong, or should I expect that with the fiberglass surface? Just not sure what's going on here. Thanks.
 
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Old 11-01-15, 09:31 AM
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Did you rinse off the door after cleaning with the TSP?
 
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Old 11-01-15, 09:33 AM
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Yes, I wiped it down again after using TSP.
 
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Old 11-01-15, 02:52 PM
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As Joe mentioned, TSP residue will cause adhesion issues if it isn't sufficiently rinsed off!
Why did you need to spray 3 separate coats? While I've not painted many fiberglass doors, I've sprayed 100s of metal doors and almost always covered them with just one coat. What size airless? what size tip? I've never needed to thin enamel with any of the airless pumps I've used.
 
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Old 11-01-15, 07:33 PM
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I guess I could have done 2 coats, but I chose 3 just to make sure I had nice even coverage. I'm a novice at spraying. I was using a basic HomeRight airless electric sprayer. No special tips or anything like that, no adjustable pressure. I practiced on some cardboard beforehand. The HomeRight sprayer came with instructions on how "thin" the paint had to be in order to be used, so that's what I was going on.....

Could it be that I just need to wait for the latex to cure?

Thanks.
 
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Old 11-02-15, 03:25 AM
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Latex paints can take a week or so to cure although they will never dry to as hard a film as oil base coatings do. Both cool temps and a heavy or multiple coats will slow down the curing process.

I don't know anything about that particular airless and not much about any non commercial airless. I understand the non interchangeable tip but surely there must be some type of pressure adjustment.
IMO it's harder to spray with those types of tips
 
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