Conversion coat for 2 part polyurethane? - SailNet Community
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post #1 of 14 Old 12-20-2006 Thread Starter
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Conversion coat for 2 part polyurethane?

I am currently refinishing my deck and have what I suspect to be a typical problem. The previous owner painted the boat with an unfamiliar paint, but I am sure it is not a 2-part system. I now want to paint with a 2-part polyurethane but I cannot remove all of the old paint through sanding (and I don't want to use any chemical strippers). Is there such a thing as a conversion coat or primer that I can paint over the old paint. The old paint is in a good condition (i.e. it is not cracking or peeling). I have spent three days removing all of the hardware and sanding down the boat and would really like to use a two-part system if possible.

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post #2 of 14 Old 12-20-2006
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The obvious answer is to check the directions, and with the manufacturer, of the new paint. If the paints are compatible there is no need to remove old paint that is adhering well, although it should be sanded for good adhesion of the new paint. Failing all else, you can check the compatability of new and old paint by soaking a rag in the specific solvent recommended for the new paint and let it rest on the old paint for ten minutes. If the old paint comes up you will need to use a primer to seal the old paint first. The problem arises from the solvents in the new paint which will reactivate the old paint prior to flashing off. Ignoring this can cause a hopeless streaking of new and old paint as well as adhesion problems. It does not matter how long the old paint has been on for this to occur. Again, your supplier if knowledgeable, and certainly the manufacturer of the new paint should be able to advise a course of action and recommend an appropriate primer as necessary.
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post #3 of 14 Old 12-20-2006
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Peruse http://www.yachtpaint.com/usa/default.asp carefully and get a good handle for thier products - they have everything anyone needs for painting, simple to sophisticated. See what paint you think will satisfy your level of expense versus effort versus /desired result, then call their tech staff at 800-468-7589 and tell what you have, and what you want to do - they'll tell what prep is needed.

Excellent phone service, free, although the paint stuff is suitably expensive.
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post #4 of 14 Old 12-21-2006 Thread Starter
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Thanks guys,

I read through the entire yacthpaint website before posting this thread and all I saw over and over again was that 2-part systems cannot be applied over 1-part systems. So finally I did call the help-line at International and he told me that I HAD to take the old paint off and that there is nothing that I could do to avoid it. I will try the compatibility test and if that fails then I guess I have to use a 1-part paint. Regarding a primer coat in-between, it is the same problem with all of the primers, they all say that they must be used over either a 1-part or 2-part scheme...
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post #5 of 14 Old 12-21-2006
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The 2 part paint systems use VERY powerful solvents and it may well be that you do need to remove the underlying coats as suggested by the manufacturer. On the other hand, the manufacturer might just be reluctant to suggest you might get away with applying the primer just in case it bubbles up, they don't want there to be any comeback on them.

Sailaway's compatablility test is certainly worth a try... but keep in mind that it would be a shame to waste the considerable expense and effort of the 2 part paintjob just to have it turn into a royal mess. If the solvent test removes the paint, perhaps that's another avenue to investigate even though you have said you'd prefer not to go that way. IF you do in the end, make sure you have the proper respirators and equipment to protect yourselves - you'll need them to paint with anyhow.
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post #6 of 14 Old 12-21-2006
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If you are having difficulty getting the 1 part paint removed....suggest "sandblasting" with a very light stripper like baking soda...then you can prime and use the 2 part.
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post #7 of 14 Old 12-21-2006 Thread Starter
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Thanks a lot for all of the advice...one last add-on question (am I allowed one of those?). How much better is a two-part polyurethane compared to a one-part? Everything I read says that I should use a two-part because it is better than a one-part...but honestly I have never thought about it when looking at boats and so I don't know how one appears versus the other. Is the difference very noticeable?

Thanks again,
Bob
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post #8 of 14 Old 12-21-2006
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equiti...There is a difference in luster and depth of shine initially but the big difference is the one you will see 2-3 years down the road. Worth it if you have a boat you plan to keep and want to look pristine. Otherwise...slap on a 1 part poly.
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post #9 of 14 Old 12-21-2006 Thread Starter
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Thanks Cam,

So maybe I'm stressing out about this too much. Considering my boat rests in a trailer and covered by a tarp when not being used in freshwater, perhaps the 1-part would be sufficient. Sorry for the awful questions...I am a total amateur at this and really have no idea what I am doing (but at least give me credit for trying to do it right! ) If it looks like crap in two years I can sand down all 19 feet of it again and repaint. I'll think about all of my options a little bit and finally at some point I'll have to make a decision...

Have a nice night,
Bob
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post #10 of 14 Old 12-21-2006
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Try a test area first before making a final decision, but if it stays covered when not in use, I am not sure a one part isn't the answer.

Last edited by pigslo; 12-24-2006 at 02:07 AM.
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