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2 Part epoxy barrier paint

Discussion in 'Big Boats' started by sailme88, Oct 3, 2016. Add this thread to a FAQ

  1. sailme88

    sailme88

    Joined Jan 19, 2010
    145 posts, 41 likes
    Catalina Catalina 34
    US Casco Bay
    Hi all,

    I am having the old bottom paint removed. Following this my plan is fair out any blister or gel coat imperfections and then apply a 2 part epoxy barrier coat.
    The question: Have any of you used a 2 part system i.e. Interlux, Pettit etc. and were the results as you hoped for?

    Pros//cons

    Thanks,

    Rick
     


  2. Ralph Johnstone

    Ralph Johnstone

    Joined Jan 4, 2006
    2,449 posts, 281 likes
    Hunter H-310
    CA West Vancouver, B.C.
    Applied five coats of Interprotect 2000 back in 2001, followed eight hours later by one coat of black Micron CSC and then one coat of blue a couple of hours later. Left to completely set for a week (while I cut polished off all the old the sanded bottom paint from the deck) and have never looked back.
     


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  3. woodster

    woodster

    Joined Sep 15, 2009
    6,240 posts, 263 likes
    S2 9.2a
    US Fairhope Al
    i used west system barrier coat with there additive...i applied 6 coats and satisfied with the results
     


  4. centerline

    centerline

    Joined Mar 20, 2012
    3,983 posts, 188 likes
    Cal 34-III, MacGregor 25
    US Salem, Oregon
    there are a few different barrier coats available and all of them have been tested... failures are due more often to preperation and procedure than it is the product used, assuming it was a brand name product that was used.

    when applying an epoxy barrier coat, its almost madatory for the hull to set and dry out for at least a couple months... even if you have no visible blisters, the gel coat does absorb a small amount of moisture and should be allowed to dry so no moisture is sealed in under the barrier.... it cant dry out in a couple weeks
    and if there are any very small unseen blisters they could also have a chance to dry out and so could never cause a problem later.

    sometimes when one hears of a barrier coat failing its job, it can almost always be traced to a hurried and improperly prepped barrier coat job....

    a hull with hundreds of very small blisters, can actually be dried out if given enough time, and the blisters will recede. large blisters should always be opened up, allowed to dry and then ground out, and filled.
    when the barrier coat is applied, the dry hull is sealed....

    this practice is always recommended but not always done, and when its not the chance of blisters reappearing sometime later are much greater.
     


    Last edited: Oct 5, 2016
    sailme88 likes this.
  5. Joe

    Joe

    Joined Jun 1, 2004
    6,645 posts, 409 likes
    Catalina 27
    US Mission Bay, San Diego
    I can't think of any "cons" to putting a barrier coat on your boat... the most important thing is to follow the instructions and watch your weather. The Interprotect product, like all epoxies, will be pretty susceptible to temp and humidity. You need to sequence the coats over a relatively short period of time... again.. study the instructions... Interlux has a lot of videos and a customer service line.

    I can't imagine leaving my boat out of the water for 2 months to let a few blisters dry... I made repairs on my boat 16 years ago with one day drying time and a little heat gun....before applying the 3M product. No failures or new blisters in all these years.
     


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  6. CloudDiver

    CloudDiver

    Joined Sep 8, 2014
    2,541 posts, 421 likes
    Catalina 22 Swing Keel
    US San Diego
    I had blisters... Stripped the old bottom paint AND the gelcoat down to bare glass below the Boot Stripe. Stripping the gelcoat is NOT required, but in yards they do this with a machine that peels it. I let my hull dry inside of my shop for two months. I used straight epoxy resin and then a single layer of 8.9oz cloth w/ resin. Then faired and painted with 2 gallons of Interlux Interprotect, then bottom, paint. Still haven't been in the water yet but I'm close, LOL.

    The question is, DO you actually have blisters? If you do, like Centerline suggested, you will need to let it dry out for several weeks after removing the bottom paint. If blisters are present it will become obvious, after sanding off the old bottom paint you will end up with various sized 'spots' where the gelcoat is sanded off to bare glass. That's because the osmotic pressure has lifted the gelcoat slightly and you will end up taking off that raised area while sanding the old bottom paint. Any bad blisters that are large and have formed the styrene smelling goo on the inside must be ground out.
    Don't fill anything until after the 6 to 8 week drying period. Believe it or not, one thing that speeds drying is freshwater rinsing the hull once a week, kinda the same concept as hosing down concrete as it cures. Small blisters can just be filled with epoxy filler (I like Interlux Water-Tite, easy 1:1 mix). Larger ones it would be a good idea to lay in layers of new glass tape with epoxy.
    I used 2 gallons on a 22 ft hull, keel, and rudder... You would need at least 3. Use a 1/4" nap roller, don't mess with foam rollers, they will break down and fall apart while not putting on a good enough film thickness.
     


  7. sailme88

    sailme88

    Joined Jan 19, 2010
    145 posts, 41 likes
    Catalina Catalina 34
    US Casco Bay
    Thanks, I was wondering if after baring the hull I should wait until spring to barrier coat..
     


  8. sailme88

    sailme88

    Joined Jan 19, 2010
    145 posts, 41 likes
    Catalina Catalina 34
    US Casco Bay
    Here in Maine you have to take the good with the bad.... a weather shortened season requires the prudent to haul out for 6-7 months... a small price to pay when one sails the best grounds in this country...
     


  9. sailme88

    sailme88

    Joined Jan 19, 2010
    145 posts, 41 likes
    Catalina Catalina 34
    US Casco Bay
    Can't tell if blisters are present. Multiple layers of bottom pain in various states of condition.
     


  10. CloudDiver

    CloudDiver

    Joined Sep 8, 2014
    2,541 posts, 421 likes
    Catalina 22 Swing Keel
    US San Diego
    Just get her sanded fully as soon as possible. A clean bottom will tell the story. Essentially, yes... wait till spring to barrier coat and you should be totally fine.
     


  11. Joe

    Joe

    Joined Jun 1, 2004
    6,645 posts, 409 likes
    Catalina 27
    US Mission Bay, San Diego
    Minor blister repair is far less intensive that CloudDiver's process. When you haul your boat.. you'll easily notice any blisters, bottom paint won't hide them... but they will shrink the longer you leave the boat out of the water. So mark them and follow the instructions in this 3M link. Unless you have serious delamination and hundreds of blisters... this solution will work fine. Warning.... be really careful with power sanders and grinders around your gelcoat..... I used a sharp chisel to puncture them initially... then carved out a large enough area so I could rinse and dry..... When you prep for repair... use a slow speed rotary sander with 150 grit or higher.to feather out the opening. The 3M repair kit uses a "vinylester" filler.... it is very hard when it dries..not easy to sand... so get it smooth when you apply it. I recommend a a pair of metal, rather than plastic, spreaders to mix and apply the filler....and to smooth it over the repair area.

    After getting the blisters fixed.. you can develop you plan of attack for the barrier coat project. Good luck.
    By the way, blisters tend to be non re occurring... there's like a window of time during the boat's life when they occur.... Catalina Yachts had their worst epidemic with boats produced in the late 70's to early 80's... With luck you may have no problems at all..... I hope that is true.
    3M Minor Blister Repair PDF
     


    centerline likes this.
  12. CloudDiver

    CloudDiver

    Joined Sep 8, 2014
    2,541 posts, 421 likes
    Catalina 22 Swing Keel
    US San Diego
    * Minor blister repair is far less intensive that CloudDiver's process - Sure, if you are ok with risking recurrence. The OP has the opportunity to let the hull dry while on the hard for the winter, he should do it.
    * you'll easily notice any blisters, bottom paint won't hide them - Obvious, fully formed blisters, true. However, water can be present in the laminate and is 'in process' of forming a blister but the osmotic pressure hasn't built to a point where it is obvious.
    * Warning.... be really careful with power sanders and grinders around your gelcoat... - Yes be careful around your topsides shiny gelcoat, for sure. On the bottom when stripping bottom paint, your statement is totally wrong. I had to use 40 grit ceramic belts to get the majority of bottom paint off, followed by 80 for finer but cleaning. The Gelcoat is even tougher, same 40 grit belts and serious pressure to strip the gelcoat completely. The OP wants to barrier coat, the bottom gelcoat needs to be prepped with 80 grit at a minimum.
    * I used a sharp chisel to puncture them initially... then carved out a large enough area so I could rinse and dry..... - I though we were talking about 'minor' blister repair? Carbide bur is far more effective.
    * When you prep for repair... use a slow speed rotary sander with 150 grit or higher.to feather out the opening. - Um, No. Waste of time and you will get no where.
    * The 3M repair kit uses a "vinylester" filler.... it is very hard when it dries..not easy to sand... so get it smooth when you apply it. - Vinylester is better than polyester filler, but not as good as epoxy. The advantage to the 3M filler is that it has glass fibers in it, so it would be good for larger blisters... Interlux Watertite is epoxy based and easy to sand, good for small blisters. For larger ones I would still go with some glass tape and epoxy resin.
    * By the way, blisters tend to be non re occurring... - That's true if the repairs are done correctly, the most important part being adequate drying time followed by a correctly applied barrier coat with proper film thickness. There are dozens of horror story around the web about expensive 'professional' yard blister repairs where new blisters formed a year or two later... because yards rush the jobs and don't let the hull dry out enough; it isn't new water molecules coming in through the barrier coat, its the water that was already in the laminate that got sealed back in under the new paint.

    You have to understand the 3M repair document is designed to get you to buy all of those 3M products shown.
     


  13. centerline

    centerline

    Joined Mar 20, 2012
    3,983 posts, 188 likes
    Cal 34-III, MacGregor 25
    US Salem, Oregon
    Everyone, from the prospective novice boat buyer to the so called "professionals" seem to have their own idea as to what the actual severity of any given blister is, when in fact its pretty straight forward to those of us who have studied them and done numerous blister repairs, and learned what works and what doesnt.... and I can only say this after utilizing and gleaning information from all the scientific studies and work that has been done on the problem in the past 40 years.

    within the last 20 years, the largest percentage of so called "professional" jobs that are expensive and have failed, were more than likely done in a yard by a minimum wage worker who had no clue, didnt care about the boat or its owner, but was being pushed to get the job done by someone who was only slightly more qualified, when all the worker wanted to do was to be anywhere else in the world, as long as it wasnt at work making fiberglass dust..... just because the yard charges a lot for the work being done doesnt mean the employee doing the work is qualified to do it, or that his supervisor is even qualified.

    drying time (and patience) is always your friend when planning to barrier coat...
    large blisters, quarter sized and bigger should normally always be ground and filled.... (there are exceptions)
    the small fingernail sized blisters that sometimes will cover the entire bottom, or large area of the bottom, and makes the bottom look pebbly, can almost always be dried out to where they will recede back down... sanded over a little and they will never show again until the gelcoat has a chance to suck up water again.
    attempting to perforate all the blisters is good, but only so they can bleed out and speed drying time. some of these small blisters will inevitably be missed, but with adequate drying time, it wont matter..

    the reason that it can recess back down is not a direct result of the water behind it being removed, but because the gelcoat DOES absorb water, and when it does, it wants to swell a bit, (like a sponge, piece of wood or other object that can absorb water) so, where the water can get behind the gelcoat in the tiniest recess, it will absorb into the surrounding polyester and weaken even more an already weak adhesion, to allow the gelcoat to lift away from the resin laminate behind it, and once it begins to come loose, the swelling of the gelcoat finds relief in pushing outward and doming/blistering, which pulls at the edges of the weak adhesion within and causing the blister it to grow larger until it gets big enough that the blister has enough surface area to absorb all the swelling and lifting within its domed surface, or the adhesion is so strong that it can lift away anymore... due to the doming action allowing the gelcoat room to swell, its extremely rare to see a blister as large as ones hand.
    the mil thickness of the gelcoat at a given area, usually has a direct effect on the size that the blister can grow to.
    thick gelcoat will not have fingernail sized blisters, and thin gelcoat will rarely have large blisters.

    nearly all blisters are NOT a hull threatening problem, but they are ugly, can slow down a racing boat and likely to cause the resale value of the afflicted boat to plummet.
    But when one opens a large blister and finds a large dry area of resin starved laminated behind the gel coat, that goes deep, then there is a problem and time to break out the big money....this is a structural problem.

    and I will also agree on a few other points made...
    if ones intent is to seal the moisture out forever, take the time and precautions necessary to make sure you dont seal any in....

    the bottom of the boat can take some severe abuse with grinding discs and sanders, as long as the material taken away is replaced with something equally as strong or beneficial....

    the less disruptive you can be to the bottom of the boat and still do a quality repair, the less time it will take to complete the task and the easier it will be..
     


    Last edited: Oct 6, 2016
  14. Joe

    Joe

    Joined Jun 1, 2004
    6,645 posts, 409 likes
    Catalina 27
    US Mission Bay, San Diego
    [QUOTE="CloudDiver, post: 1330319, member: 127132
    You have to understand the 3M repair document is designed to get you to buy all of those 3M products shown.[/QUOTE]
    Yeah.... but.... it works!
     


  15. sailme88

    sailme88

    Joined Jan 19, 2010
    145 posts, 41 likes
    Catalina Catalina 34
    US Casco Bay
    UPDATE UPDATE UPDATE...Had the opportunity to speak with an Interlux rep at a boat show.. The advise is thus: You can apply barrier coats with up to 6 mos between coats. BUT, your first ablative needs to be applied while the last barrier is still tacky ! Adhesion failure during the 2nd year out is a real possibility.
     


  16. Gunni

    Gunni

    Joined Mar 16, 2010
    5,836 posts, 1,434 likes
    Beneteau 411 Oceanis
    US Annapolis
    Bad advice. You might want to ask the Interlux rep why published Interlux guidance for barrier coat specifies a maximum 24 hour re-coat time (5 hours if it is really hot). All epoxies rely on one of two types of bond, 1)chemical, or 2) physical. By recoating prior to full set of the epoxy you obtain the maximum chemical bond strength. If you wait 6 months to finish your barrier coat build you will need to sand the hardened layer to provide tooth (a physical bond)...and you do increase the odds that of adhesion failure by not doing the job as directed.
     


  17. sailme88

    sailme88

    Joined Jan 19, 2010
    145 posts, 41 likes
    Catalina Catalina 34
    US Casco Bay
    Gunni,
    Following your comment I went directly to InterLux. They were specifically asked about the application and they responded,

    "Yes, you need to apply the antifouling over a tacky barrier coat. Tacky to the touch with no paint transfer to your fingers."

    This is a direct quote from InterLux....
     


    Last edited: Apr 3, 2017
    Gunni likes this.
  18. Gunni

    Gunni

    Joined Mar 16, 2010
    5,836 posts, 1,434 likes
    Beneteau 411 Oceanis
    US Annapolis
    Yes, when you get the barrier coat epoxy build complete you apply the antifouling paint to a "thumbprint soft" final layer of epoxy. That is different from doing the barrier coat buildup which is typically 4 or more coats as you work to a 10 mil barrier thickness, those need to be applied per the schedule I provided in the linked Interlux guidance doc.

    I'm hoping that my comments help you to avoid the many, many failures and wasted hours of others as they do this job. This is tedious work, do it scrupulously right. Interlux has lots of exact guidance on their website.
     


  19. Interlude 2

    Interlude 2

    Joined Thursday
    2 posts, 0 likes
    Catalina 380
    Interlude US Longport, NJ
    I’ve been selling barrier coatings for years made by Interlux, Pettit and now Sea Hawk. Now they are a recommended bottom paint primer for new boats. Just follow manufactures instructions for each one. I prefer Sea Hawk products, personally. Blistering problems are now rare on boats manufactured in the last 20 years or so since the problem was discovered and addressed at resin and boat manufactureing along with proper bottom paint priming processing having been instituted. It was a bigger issue in the 90’s.
     




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