bottom paint not sticking

J

Jim S

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Long Island Sound, Clinton CT
I have several spots where the paint never sticks to the hull, and barnacles form during the season creating drag. I have tried sanding these spots extra good, have cleaned them with extra solvent, primed, and painted again, the paint never sticks tho. I have been told I could spot prime with barrier coat. I do not have the resources to completely strip the hull. Any ideas?
 
Usually if the new paint doesn't stick it is because of either contamination on the hull, wax, release agent etc. for unpainted hulls, or having previous paint that is not compatible with the new. Sanding is recommended but if the spots you are sanding were painted with incompatible paint, the new paint could have problems. In many cases, after sanding and after cleaning with the appropriate solvent. a coat of primer is needed. If you don't know what paint was used before, assume it is not compatible. Primers are easier to apply than barrier coats and less expensive too. Make sure you use a product recommended by the bottom paint manufacturer.
Not following the instructions can also lead to problems. A paint that is too cold or coats applied without the proper drying time can fail. Launching the vessel before the recommended time can also be an issue.
Also makes ure you do not use a roller or brush that is contaminated with something than can cause issues.
 
Thanks for the info. The spots are down to bare fiberglass. I have sanded and cleaned with solvent, acetone, and other "agents" over the years, nothing seems to work. I have also used a primer a few years back, Sea Hawk something or other, I can't remember. Can you recommend a specific primer? Maybe I will have better luck. My last option is to spot prime with barrier coat. I do not have the option of stripping the hull completely.

Thanks!
 
Jim S said:
Thanks for the info. The spots are down to bare fiberglass. I have sanded and cleaned with solvent, acetone, and other "agents" over the years, nothing seems to work. I have also used a primer a few years back, Sea Hawk something or other, I can't remember. Can you recommend a specific primer? Maybe I will have better luck. My last option is to spot prime with barrier coat. I do not have the option of stripping the hull completely.

Thanks!
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What is important is that you use the primer recommended by the manufacturer of the final bottom paint.
It is a lot easier to apply primer than barrier. Interlux 2000 for example, requires 4 coats, separated by specific times based on ambient temperature.
You probably need to use a dewaxing solvent for the bare fiberglass. Again, check with the bottom paint manufacturer.
It sounds like the hull was not prepped correctly the first time. Unfortunately, it is possible that other areas may also peel over time. The only way to protect against that is is remove all the bottom paint and start over. If on the other hand, the same spots peel, redoing theose areas should do the trick.
 
Does water bead up at all or clear out more quickly in that area vs others? Ever spray silicone around that area? Silicone can cling to a surface for a long time....even with solvents it just smears around but a light film still stays put....that would definitely create a no bond area....
 
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