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Thread: Epoxy paint compatibility problem?

  1. #1
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    Default Epoxy paint compatibility problem?

    Before repainting some woodwork on my boat, I sealed an area where a puddle of water tends to sit and soak into the wood with System Three epoxy. After it was hard, I put the first coat of oil based enamel paint on the hatch cover. Three days later, the paint is dry and hard everywhere except over the epoxy where it is still tacky.

    Any ideas? Will this resolve itself?

    Epoxy was hard and sanded lightly before painting.
    Roger Long

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    Default Re: Epoxy paint compatibility problem?

    Did you let your epoxy to cure at least a solid week before sanding it? The curing time of epoxy is far longer than the manufacturer want to tell. A solid week at 70 degree I consider that a minimum. The drying time of course is faster.

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    Default Re: Epoxy paint compatibility problem?

    Okay. I am in the same boat. Put down some epoxy on the bottom of the batto and painted it a couple of days later after sanding it. The primer seemed to stick but not the paint. Clearly I did not wait long enough for the epoxy to dry.

    Question what do I do now?

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    Default Re: Epoxy paint compatibility problem?

    With the System 3 resins you need to read their information carefully. I've had issues with getting varnish to cure over the stuff. For those who may question: yes, the epoxy was correctly mixed and cured for over two weeks at 70+ degrees. Yes, the amine blush was removed with ammonia and water and soap and water after wet sanding. If I'm applying UV protection over the System 3 resin, I use their spar urethane. If painting, they offer a special primer to use prior to painting.

    Using the same prep, I haven't had any issues using good spar varnish or urethane over West System epoxy. Haven't used paint over West System yet.

    Roger, it sounds line there was some amine residue.
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    Default Re: Epoxy paint compatibility problem?

    I have dealt with this many times ... with oil based paint. . . its an easy fix. As a matter of fact, any time I am painting atop System III ... I either prime (if I have time) or add Cobalt dryer to my paint. Go to a local art store or online and get a bottle of Cobalt Dryer (Cobalt Blue) .

    Grumbacher Cobalt Dryer https://www.alvinco.com/shopping/fam...43_Item_GB5942

    Pour out enough paint in a container to repaint the area you are talking about and add about 8-10 drops of cobalt dryer per ounce of paint. Stir and repaint the project area that has to be covered to get a nice finish. This second coat laced with cobalt dryer will enable the problem area to dry and you will be happy with the results. Your paint job will be dryer faster and a bit harder.

    If applying a first coat in the future atop System III epoxy, add about 5-6 drops of cobalt dryer per ounce of paint and you will not have any problems. Cobalt dryer works fine with alkyd enamels and varnish and polyurathane.

    System III general purpose resin and their new Silvertip gives off free amines for quite a while and they interfere with the dryers in the paint. Adding a bit more dryier just replaces the dryer interefered with and all is well.

    Good luck,

    RodB

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    Default Re: Epoxy paint compatibility problem?

    I did not use System Three. What should I be doing to get the paint to stick? Let the epoxy dry longer and then sand or sand now and then let it dry?

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    Default Re: Epoxy paint compatibility problem?

    We've had this discussion about using the cobalt before...

    Bobcat, it is mostly about good surface prep and following the manufacturer's instructions - for both the epoxy system and the coating. Some recommend special coatings or primers to for either overcoating or as a tie layer before paint. Some just require good cleaning with soap/water, ammonia and water or a bit of denatured alcohol and some sanding to degloss the epoxy. Most reputable epoxy and coating companies have very good technical support.
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    Default Re: Epoxy paint compatibility problem?

    I always use an epoxy 2 part undercoater between resin and topcoat.
    Usually interlux 404/414

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    Default Re: Epoxy paint compatibility problem?

    I did not use System Three. What should I be doing to get the paint to stick? Let the epoxy dry longer and then sand or sand now and then let it dry?
    If your epoxy is mixed properly and it cures hard... then the most likely reason the paint won't dry is because of the free amines that will continue to come off the curing epoxy for weeks and weeks. Most epoxies that are cured and you want to paint the surface... must be cleaned and scrubbed at minimum with scotchbright and clean water. If you can, a primer (or tie coat .... System Three recommends their Clearcoat for this) is the way to go, if you don't want to prime, then Cobalt Drier works fine especially in situations where you need to move on with a job and need to paint sooner than later. I can speak for myself... System Three and their technical department will tell you this, I know, I asked them. If you paint on top of cleaned and sanded System Three General Purpose resin/hardener or their new Silvertip... you will have paint drying problems 100% of the time with standard Alkyd enamels and most likely many other coatings. FYI... gelcoat will not harden atop System three unless you apply the tie coat they recommend Clearcoat or a primer as a barrier coat.

    The paint sticking is mostly the epoxy surface being clean... and sanded or scotchbrighted so that it has some tooth. Paint drying is a different matter as above. Yes there are some epoxies that will not impede paint drying and according to Todd Bradshaw, he has painted directly on top of West many many times with no paint drying problems.

    If you mixed your epoxy right and it is cured (hard) then the Cobalt dryer will work in helping your paint dry. I guess you could remove the paint and try again???...

    We've had this discussion about using the cobalt before...
    Yes we have... two guys here have asked about the paint not drying on top of epoxy... I offer a solution...what do you offer? Some good information that needed to be considered before they painted on top of the epoxy. The solution I offered is how to deal wlth the situation they are in now, ... Cobalt dryer is a very useful tool in speeding up drying in paint or varnish... or enabling paint to dry thats already been applied and is not drying because of free amines coming off of curing epoxy. This information was passed on to me by someone who has certainly designed and built more boats with epoxy than many on this forum added together. I have used Cobalt Dryer many times and it works like a champ.

    How about addressing the question as to how to deal with the situation they are in now... ie., paint already applied to curing epoxy and severe retarded drying??? Any magic tricks you can offer?

    RodB
    Last edited by RodB; 03-15-2011 at 12:10 AM.

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    Default Re: Epoxy paint compatibility problem?

    Quote Originally Posted by RodB View Post
    Yes we have... two guys here have asked about the paint not drying on top of epoxy... I offer a solution...what do you offer? Some good information that needed to be considered before they painted on top of the epoxy. The solution I offered is how to deal wlth the situation they are in now, ... Cobalt dryer is a very useful tool in speeding up drying in paint or varnish... or enabling paint to dry thats already been applied and is not drying because of free amines coming off of curing epoxy. This information was passed on to me by someone who has certainly designed and built more boats with epoxy than many on this forum added together. I have used Cobalt Dryer many times and it works like a champ.

    How about addressing the question as to how to deal with the situation they are in now... ie., paint already applied to curing epoxy and severe retarded drying??? Any magic tricks you can offer?
    RodB
    Rod, I wasn't specific as I don't know the particular epoxy resin system that they are using - and neither do you. I used general recommendations that apply to over-coating epoxy for that reason. The solution will most likely be vendor and material specific - as you well know, these resins behave similarly, but are not all the same. I'm trying to lead the OP's to good resources for their specific problem.

    Applying cobalt dryer to a coating that is already on the surface of the hull? How do you figure on doing that? Really. You could mix up another batch of your coating with the dryer in it and try to apply it over the uncured mess that you have, but I think you'd make a greater mess. You could try to brush it on, but you'll be effecting just the surface of the coating, not the interface layer between the epoxy and the coating as it will not be thoroughly intermixed. How will you determine an appropriate concentration? Also, part of the previous discussion included some of the adverse reactions when using cobalt dryers - what about those issues? (Cracking of the coating layer, hard "shelling" without good bonding, cobalt toxicity, etc.) Specifically from a vendor of the Grumbacher stuff (an Artist's supply...)

    Driers are not recommended to be used indiscriminately. Caution must be exercized, a drop goes a long way. Too much will cause cracking.
    Cobalt dryers do have a place in curing coatings and accelerating cures in oil-based and alkyd systems. I will not argue that fact. I've used them in certain applications and have generally had good results when following the recommendations of both the varnish vendor and the cobalt dryers instructions. However, this looks like a place where this use after the fact, without vendor interaction, would be rife with problems.

    To answer your other question specifically, if the drying is process is retarded, the best situation is to make sure the environment is warm enough and wait. There isn't much magic here. If it doesn't cure, you've got to remove it all, figure out what went wrong and start again using the proper materials and methods.

    Roger most likely still has residual amines and adding cobalt will not get a good result. He needs to remove the coating in this area, properly prepare the surface by sanding and removing the amines before priming with Clearcoat or the System 3 primer and then coating. Bobcat wasn't particularly specific - he had a primer that cured, so the issue would appear to be between the primer and the coating, not the epoxy and the coating. However, this doesn't mean he still doesn't have an amine issue like Roger does. There isn't enough information yet to recommend a solution.

    The best place to trouble-shoot that is with the vendor's technical support who are the experts on the subject.
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    Default Re: Epoxy paint compatibility problem?

    Applying cobalt dryer to a coating that is already on the surface of the hull? How do you figure on doing that? Really. You could mix up another batch of your coating with the dryer in it and try to apply it over the uncured mess that you have, but I think you'd make a greater mess

    Roger most likely still has residual amines and adding cobalt will not get a good result. He needs to remove the coating in this area, properly prepare the surface by sanding and removing the amines before priming with Clearcoat or the System 3 primer and then coating. Bobcat wasn't particularly specific - he had a primer that cured, so the issue would appear to be between the primer and the coating, not the epoxy and the coating. However, this doesn't mean he still doesn't have an amine issue like Roger does. There isn't enough information yet to recommend a solution.
    I agree, the first step is to wait with some heat and see what happens... but if the paint has not dried in a couple days... the following is worth a shot, as I have seen it work several times.

    If the paint has already been applied to epoxy and ... if the epoxy is hard (mixed right) you have nothing to lose by applying another coat of paint with a bit more cobalt dryer. This procedure was recommended to me several years ago by Tracy Obrien and it works... as I have tried it. All you have to lose is a little time and if the 2nd coat works, your done... if not ... you remove all of it with a chemical strip or sanding... a very rational approach and I know it works if the free amines are the problem impeding the paint drying.

    Further... I have done numerous fiberglass repairs using epoxy... where I did not want to take the time to prime over the cured epoxy and time was important... and I just cleaned her up good, (scrubbed the epoxy surface with water and a scotchbright pad... then applied paint with cobalt dryer 6 drops per ounce... the paint was dry within a few hours. DONE...

    RodB

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    Default Re: Epoxy paint compatibility problem?

    Rod, the concern that I have is that if you apply another coating doped with the cobalt dryer, you have a few major issues. First, the cosmetics of the coat may be questionable - anyone who has applied paint over wet or partially cured paint knows the pitfalls of that from the POV of crazing, wrinkling or cracking of the coat from the dis-similar curing of the layers. Second, there may be cracking of the coating due to the cobalt dryer itself. and last, you can wind up with a layer of candy coated goo where the first layer of coating doesn't completely cure through and provides a weak bond, both mechanically and/or chemically to the layer beneath it. It seems to me that the secondary coating is setting you up for potential failure of the coatings or having a "suspect" layer that may fail prematurely.

    In any of these cases, you will be back at square one trying to solve the problem by sanding another time and re-coating to get good cosmetics or removing both the original coating as well as the secondary coating. Would you not agree that it would seem to be best to avoid this by first trying the "wait and see" approach and then cleaning up and using the manufacturer's recommended methods?

    I find soap and water or ammonia and water with Scotchbrite or the like to be necessary to get the waxy amines off the surface. If you use just abrasive or abrasive and water, it seems the amines just get smeared around.

    I should add one thought regarding the System 3 Clearcoat - while they claim it is an amine blush free product, I'd still treat it like it was a potential issue and wash the amines away and abrade the surface before over-coating.
    Last edited by Canoez; 03-15-2011 at 09:02 AM.
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    Default Re: Epoxy paint compatibility problem?

    Well, for the data point and learning experience this project can provide, here is what I am doing after scraping off the soft paint.

    I scrubbed with Acetone and sanded last night and put some small test patches on. This morning, they were like the paint had just been applied. Not even tacky.

    I asked for Cobalt Blue at the art supply store and they told me it was a paint. Maybe it works because of the Cobalt but they seemed familiar with the issues and sold me a bottle of cobalt dryer, which turns out to be the Japan Dryer I've heard of before. I've applied paint with it mixed in as a thin coat and we'll see what happens.

    This is a small and out of the way area so it's a good place to experiment. I'll let you now how it turns out.

    Thanks to everyone for all the great information.
    Roger Long

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    Default Re: Epoxy paint compatibility problem?

    Just to satisfy your skepticism Canoez, I checked this AM with Mr Obrien and asked a few questions mostly ones I knew the answer to already. To reiterate... if epoxy is cured and hard... and your paint (most any paint or varnish that dries when exposed to oxygen...) is having drying problems... Colbalt Dryer is what is the catalyst/dryer used in these paints. Manufacturers put as little Colbalt Dryer as possible in paints and varnishes because they do not want them to solidify or gel in the can on the shelf of the stores. Because they use so little DRYER... the free amines from curing epoxy will retard if not stop the drying in many paints. If you think of the Colbalt Dryer as a catalyst, perhaps you will feel less worried about how it will affect the paint.

    If you have already applied the paint and its not drying... then applying a second coat laced with Cobalt Dryer can't hurt anything and I have seen this work numerous times. It works with varnish and paint. I'm not recommending anything that I have not tried numerous times and I know it works. It works with Alkyd enamels and single part polyurathanes.

    In any of these cases, you will be back at square one trying to solve the problem by sanding another time and re-coating to get good cosmetics or removing both the original coating as well as the secondary coating. Would you not agree that it would seem to be best to avoid this by first trying the "wait and see" approach and then cleaning up and using the manufacturer's recommended methods?

    I find soap and water or ammonia and water with Scotchbrite or the like to be necessary to get the waxy amines off the surface. If you use just abrasive or abrasive and water, it seems the amines just get smeared around.

    I should add one thought regarding the System 3 Clearcoat - while they claim it is an amine blush free product, I'd still treat it like it was a potential issue and wash the amines away and abrade the surface before over-coating.
    Are you trying to improve the quality of the advice here or point out faults or errors you think you may have found?.
    Waiting and seeing just makes it more unlikely that the second coat laced with Cobalt Dryer will be as effective. 24 hours is enough time to see if the paint's dryers have been interfered with. I think the sooner the second coat is applied the better.

    One epoxy surface prep for painting... personally, I have always used a quick spray with a 10% solution of Ammonia and water i followed with plain water wash and scrub/sanding, but many texts on this subject say warm water and Scotchbright work fine... My previous comments were what is in many references on this exact subject... scrubbing off amine blush. . . with a final wipe with a rag soaked with clean water.

    I have used System Three Clearcoat as a tie coat for both paint and Gelcoat. Gelcoat is very finicky and will not go off if applied atop curing epoxy. Applied atop System Three's Clearcoat it goes off fine. I would mostly likely clean it and sand it with 400 grit before spraying gelcoat but it works as System Three says in my experience.

    I scrubbed with Acetone and sanded last night and put some small test patches on. This morning, they were like the paint had just been applied. Not even tacky.
    I think you scrubbed off the paint and are still left with the same problem.... unless you use an appropriate primer or add Cobalt Dryer.

    I asked for Cobalt Blue at the art supply store and they told me it was a paint. Maybe it works because of the Cobalt but they seemed familiar with the issues and sold me a bottle of cobalt dryer, which turns out to be the Japan Dryer I've heard of before. I've applied paint with it mixed in as a thin coat and we'll see what happens.
    Roger, if you read what I posted earlier in the thread... I recommended.. COBALT DRYER... I posted the link again below ... Japan Dryer does not work as well as Cobalt Dryer ... they are not the same although Japan Dryer does have some Cobalt Dryer in it... I specifically asked about this process and substituting Japan Dryer for Cobalt Dryer and was told years ago that Japan Dryer was not nearly as effective and a waste of time.

    Cobalt dryer is not a paint but a very dark blue/purple liquid like a solvent. The link below shows what I recommended exactly. Your results will be dry paint if you used COBALT DRYER as you said. I have seen Cobalt Dryer and Cobalt Blue confused with each other, so that is why I mentioned it earlier in this thread. I should have left it out, but I did put the link to Cobalt Dryer. On this forum we all need to be very precise to insure correct information and no confusion. Sorry.

    Grumbacher Cobalt Dryer https://www.alvinco.com/shopping/fam...43_Item_GB5942

    Good luck,

    RodB
    Last edited by RodB; 03-15-2011 at 04:07 PM.

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    Default Re: Epoxy paint compatibility problem?

    Rod, I think you are missing the point here.

    Roger has an issue as does Bobcat. The issue here is whether or not the proper methods, materials and conditions were used. If so, the coatings should cure properly and reliably as sold. It should not be necessary to 'doctor' anything unless the manufacturer recommends it. Period.

    If there is a problem with the cure, the first order should be to figure out what the problem was, then deal with that, not necessarily band-aid things. If you don't figure out what the issue is, you may be doomed to repeat it. There may be an actual batch problem - you'd never find that out if you don't talk to the vendor or manufacturer.
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    Default Re: Epoxy paint compatibility problem?

    Quote Originally Posted by RodB View Post
    On this forum we all need to be very precise to insure correct information and no confusion. Sorry.
    Not your fault. The art supply store figured out that Cobalt Dryer is what was meant. However, the only thing they had that was a Cobalt Dryer was the Japan stuff. So far, the paint is tacky but so is the the stuff I put on a stirring stick for comparison. I've moved the hatch cover to a warmer room we'll see.

    I've been rushing all this because I'd like to get the hatch back on the boat. I painted the day after putting the epoxy on. Always before, painting has been days or weeks after the epoxy work which is why I probably haven't had problems. Most of my epoxy work I haven't painted anyway.

    We're only talking about a 3 foot x 2 inch strip here so it's not a big deal. If I were doing a hull or deck, you can be sure I would be proceeding more carefully. Thanks for the link. I may have to order some.

    Just out of curiosity, why doesn't acetone take off the amines? I thought it took off just about anything.
    Roger Long

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    Default Re: Epoxy paint compatibility problem?

    Quote Originally Posted by Canoez View Post
    The issue here is whether or not the proper methods, materials and conditions were used.
    They weren't. I'm duffing around here. They say you learn best from your mistakes so I'm trying to make as many as possible on this little patch of wood
    Roger Long

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    Default Re: Epoxy paint compatibility problem?

    I intend to do nothing for at least a week or so. The epoxy went on a week ago and the weather has been cold and very damp, not conducive to anything drying. So I will give it time to set up and then figure out what to do.

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    Default Re: Epoxy paint compatibility problem?

    Quote Originally Posted by Roger Long View Post
    Just out of curiosity, why doesn't acetone take off the amines? I thought it took off just about anything.
    It should work. There are a bunch of heavy duty solvents that do work - some are very expensive thinners and the like from the epoxy vendors and are un-necessarily expensive. I try to use more 'friendly' materials which do the same thing.
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    Default Re: Epoxy paint compatibility problem?

    If you put heat lamps on the epoxy to keep it really warm you can probably get it to harden completely and shed all its vapors in a week. Not too much heat, of course.
    I will beg you for advice, your reply will be concise, and I will listen very nicely and then go out and do exactly what I want! (Apologies to Lerner and Lowe.)

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    Default Re: Epoxy paint compatibility problem?

    Rod, I think you are missing the point here.

    Roger has an issue as does Bobcat. The issue here is whether or not the proper methods, materials and conditions were used. If so, the coatings should cure properly and reliably as sold. It should not be necessary to 'doctor' anything unless the manufacturer recommends it. Period.

    If there is a problem with the cure, the first order should be to figure out what the problem was, then deal with that, not necessarily band-aid things. If you don't figure out what the issue is, you may be doomed to repeat it. There may be an actual batch problem - you'd never find that out if you don't talk to the vendor or manufacturer.
    Canoez, I think you might be confused... and I am not missing the point. You do not seem to get the point that they said they were having paint drying problems atop epoxy. Roger specifically said his epoxy was hard... and then he painted it. Additionally, why would you assume a member here would just give erroneous advice without first hand knowledge??? I've done my testing and worked out my own understanding of these products.

    Neither one said their epoxy was soft or sticky... Also... you seem to be inferring that if the epoxy cures up pretty good in say for example... a week or two ... that the free amines will not be a problem any more..... then with "proper use of said products... and prep of the epoxy surface... that you will have no problems...

    You would be wrong. The free amines will continue to come off of the epoxy for weeks and weeks... This is true for System Three and many other epoxies.

    I do not think any of the epoxy companies say paints should dry if applied on top of their product.... they usually say do a test. If you are using an epoxy that gives off free amines you would have to do a test on paint drying over time to see the precise behavior of paint drying inhibition. Most of us just lean towards the conservative side here and adopt a procedure that works 99% of the time.

    Since I do wood and fiberglass repairs, I am usually not prepared to wait for a few weeks to paint an epoxy repair job. As I said before some epoxies and System Three is one of them... will give you paint drying interference 100% of the time even many weeks after the epoxy is supposed to cure. If I have the time, I prime with a hot solvent primer that provides a good barrier between the epoxy and the paint or use the relatively expensive System Three Clearcoat.... If not, I add a little Cobalt dryer and apply the paint.

    Hope you get the point now... dealing with where you are at, not where you could be if you did things differently...

    Originally Posted by Roger Long
    Just out of curiosity, why doesn't acetone take off the amines? I thought it took off just about anything.
    You can sand and scrub and use any solvent you want... free amines will continue to come off the curing epoxy and it has nothing to do with how much you clean the surface. The free amines will just continue coming off the reacting epoxy for a long while. In many cases, they do interfere with paint drying. In addition to proper cleaning etc of the epoxy surface... your choices are 1) prime the area before painting, 2) add Cobalt dryer a bit.. or 3) find an epoxy that absolutely does not give off free amines after a set time for curing.

    Keep us posted about your paint drying...


    RodB
    Last edited by RodB; 03-15-2011 at 11:43 PM.

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    Default Re: Epoxy paint compatibility problem?

    Quote Originally Posted by RodB View Post
    Keep us posted about your paint drying...
    Who would have thought a thread about watching paint dry could be so interesting?

    I moved the hatch upstairs to a warmer room last night and turned up the heat. This morning, the paint was no longer tacky but still had that high friction, "grab your finger when you slide it" feel. I'd say it's about half way to being dry and hard. Test sample left in the basement is completely dry but was on bare wood so a lot of solvent could soak in.

    I think the Japan Dryer must have worked. I used the amount recommended for the Cobalt Dryer so more might have worked better.

    The paint I put over epoxy in my bilge a couple years ago took weeks to fully dry but eventually became hard and has shown no signs of flaking off. I think this hatch will eventually be OK. If the problem portion was in a place where it could get stepped on or chafed, I would strip it and start over because I'm sure the paint will not be quite right. This part goes up under the companionway slide cover so is protected from both abuse and sun. If it doesn't hold up, I'll just redo it in place. The epoxy will still be under the paint to keep the water out of the wood.
    Roger Long

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    Default Re: Epoxy paint compatibility problem?

    Roger - glad to see things are coming along. I think you have been fortunate. Can you clarify your statement, "I think the Japan Dryer must have worked. I used the amount recommended for the Cobalt Dryer so more might have worked better. "

    Rod, still missing the point.

    First, it's not a personal attack.

    Second, the point is not to get to the point where you need to "solve" things in the first place by following the instructions. Roger is clear that he did not and is having problems.

    Third, some really smart chemists design and test these epoxies and coatings. They've done the testing and understand how this stuff should work and what the long-term effects of the process are. While cobalt dryer is a solution, so is following the instructions, so that the materials behave as the chemists have designed them to. The best solution is not to get to the point of having to go "outside the envelope" to make things work.

    Roger noted that his resin had cured for 1 day, probably in cool temperatures. - System 3 recommends a minimum of 3 days- at 77F! Just because the resin is hard and "tack free", it isn't necessarily fully cured and will continue to bleed amines that will cause curing issues for subsequent coatings. However, after the combination of times and temperature (3 days at 77F), the manufacturer considers the resin "cured" and then the rest of their prep and coating advice should be valid - at that point they have determined that the amines are at such a level as not to inhibit the cure of the coatings that they recommend. They do recommend test patches of coatings that they don't recommend (i.e. their own products) before you go ahead and do the whole boat - what's the matter with that advice?

    If you use System 3 epoxy, their Epoxy Book is required reading.
    Last edited by Canoez; 03-16-2011 at 08:00 AM.
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    Default Re: Epoxy paint compatibility problem?

    I think the Japan Dryer must have worked. I used the amount recommended for the Cobalt Dryer so more might have worked better.


    Roger, the next time you want to paint atop epoxy that is freshly cured and scrubbed clean... you have some options now and for pure expedience you may use Cobalt Dryer to avoid any hang ups... The use of Cobalt Dryer in this regard is more common than you might expect, and a SOP for some.

    The best solution is not to get to the point of having to go "outside the envelope" to make things work.
    True in most cases...

    Second, the point is not to get to the point where you need to "solve" things in the first place by following the instructions. Roger is clear that he did not and is having problems.
    In general, any time you need to paint over epoxy, if the time frame you have is reduced say... within a few weeks, you should test to see if you will have any problems with paint drying... Any time you have paint drying problems in this situation, Cobalt Dryer is a solution and with common sense of just adding a little, does not affect the quality of the paint matrix... based on much anecdotal experience from many ... over time. (Alkyd enamels, single part poly's ... paints that dry exposed to Oxygen) Its also cheaper and less labor and takes less time than applying a primer.

    System Three's technical dept advised me that you should use a tie coat unless you have plenty of time after using their laminating resins... ie., general purpose resin or Silvertip. . . and still did not say when the free amines are for all purposes ended. I have not found 3 days at 77 degrees to be accurate, I have still had some paint drying retardation with Alkyd enamels after two weeks in our very hot summer (85-102 days). Manufacturers recommendations are not gospel, you have to use some common sense sometimes, espeically if you are doing repair work and need the job to move along. Note: Rogers paint is drying fine with just the little cobalt drier in the japan drier he mixed in. The paint will be fine now, it is not going to self destruct someday because a bit more catalyst/drier was added to replace the original drier that was affected by the free amines. I'll trust Mr Obrien's 30 plus years designing and building boats to your general conservative theory reading of the manual, which I have read long ago and continue to refer to if necessary. My personal experience over the past 10 years backs up Mr Obrien's recommendations.

    FYI, West System's technical department says that you can paint and apply gelcoat atop their cured epoxy with no tie coat... (this assumes you scrub and clean the surface well of course). It must be true if they say so.

    I always enjoy a good debate... no offense taken or meant.

    RodB
    Last edited by RodB; 03-16-2011 at 08:59 AM.

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    Default Re: Epoxy paint compatibility problem?

    FYI, West System's technical department says that you can paint and apply gelcoat atop their cured epoxy with no tie coat... (this assumes you scrub and clean the surface well of course).
    I've found this to be true for spar varnish over West System and have not tried it with paint yet. I'll say that of late I've been finding that while it is a good product, I've personally been disappointed with the System 3 resin system. The West System 105/207 system seems to be more forgiving than System 3, albeit being more costly. The folks from MAS products were claiming that their low viscosity resin is "blush free" - I'd like to try that see if it is true and the RAKA system to see if there is a better choice than the System 3.
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    Default Re: Epoxy paint compatibility problem?

    I
    've found this to be true for spar varnish over West System and have not tried it with paint yet. I'll say that of late I've been finding that while it is a good product, I've personally been disappointed with the System 3 resin system. The West System 105/207 system seems to be more forgiving than System 3, albeit being more costly. The folks from MAS products were claiming that their low viscosity resin is "blush free" - I'd like to try that see if it is true and the RAKA system to see if there is a better choice than the System 3.
    I have wanted to do some tests with West... the Sailboat Shop I do repair for keeps it around, but I have found System Three General Purpose Resin to be absolutely reliable in any conditions (humidity and temp) and know it so well, I am having a difficult time switching. The three hardeners allow you to fine tune it so well. BTW... Clint Chase uses System Three and tends to use their Clearcoat alone many times because of its tough hard finish, thin viscosity and ease of varnishing later with no problems. The builder of the Schooner Susan here uses MAS, and although I have used it helping him over the past few years, I have not done a test to see how it affects paint drying. I would switch to another epoxy system if the cost was similar ($ 80/gal) and you never had to worry about paint or varnish drying interference. I prefer 2:1 systems over 5:1 and varying hardeners.

    The low viscosity epoxies are quite expensive... System Three Clearcoat is about $185 plus shipping for a 1.5 gallon kit. MAS thin viscosity resin is more that System Three too. Its hard to beat System Three General Purpose resin for cost and predictability and performance....

    RodB
    Last edited by RodB; 03-16-2011 at 09:15 AM.

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    Default Re: Epoxy paint compatibility problem?

    System 3's GP resins are about $120 around here for 1-1/2 gallons and $170 for the Clear Coat. West System's 105/207 in 1.33 gallon kit is $175, so comparable in cost to the Clear Coat. RAKA is running about $108 for a 1-1/2 gallon kit. MAS has their #1 economy kit which includes wood flour, thickener and pumps along with 1-1/2 gallons of resin and hardener for $182.

    I know from my discussions with both System 3 and Gougeon Brothers technical folks that both do fairly extensive testing - both application and mechanical and advanced environmental testing. I don't know much about RAKA or MAS in those regards. I did do a small amount of preliminary user beta testing of the "new" 207 hardener a few years ago. Good stuff for my application building small canoes.
    "Anyone who says they like portaging is either a liar or crazy."
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    Default Re: Epoxy paint compatibility problem?

    Do you find your mainstay product for finishing Canoes bright to be System Three's Clearcoat?

    RodB

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    Default Re: Epoxy paint compatibility problem?

    What do you guys thing of this stuff?

    http://www.epoxyproducts.com/marine.html

    and

    http://www.epoxyusa.com

    Just what is the purpose of amines in epoxy anyway if the cause so many problems? It epoxy can be made to work without them, why all these problems?

    BTW I put a heater in the room with the hatch cover and it seemed to slow down the drying of the paint, I imagine because the heat is accelerating the curing of the epoxy underneath and releasing more amines. It's dry to the touch but still feels sticky instead of slippery. I expect I could still scrape it off but it feels like it's going to harden up eventually.
    Roger Long

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    Default Re: Epoxy paint compatibility problem?

    Hmm. I've painted oil-based paint over both West and Progresive Epoxy (Oman's product) without any issues. I did wait over a week but I did not prime nor did I wash the surface. Sorry I don't know enough to contribute to a solution to the problem at hand but I throw this in the mix in case someone else reads the thread before they do their epoxy work.

    Post note: Roger--the stuff at epoxypoducts is the progressive epoxy mentioned above I used extensively. The only time I had any issues was when I mixed it with a lot of fillers. I got some failure to cure--not much and I am not claiming it is the epoxy's fault. Since it was a small failure, it was probably something I did but I could not figure out what I did wrong. It does cure very very slowly when thinned. I thinned some batches to use as a penetrating epoxy when all I cared about was sealing and did not need strength.
    Last edited by chuckt; 03-16-2011 at 09:47 AM.
    Chuck Thompson

    1955 18' Chris Craft Continental
    1950 30' Chris Craft Express
    1955 Concordia Yawl #26 (under restoration)

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    Default Re: Epoxy paint compatibility problem?

    Chuckt, what did you think of the Progressive Epoxy?

    RodB

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    Default Re: Epoxy paint compatibility problem?

    Quote Originally Posted by RodB View Post
    Do you find your mainstay product for finishing Canoes bright to be System Three's Clearcoat?

    RodB
    We've mostly used the GP resin system, primarily due to the cost -both myself and students are trying to save $$$. Cosmetics aren't bad but it does give an amber cast to the finished canoes that isn't really objectionable. I've had one student use the System 3 Clear Coat and about 6 use the West 105/207. However, on my own work, I've been using the 105/207 for the last three years. I find it to be costly, but generally worth it in terms of application "friendly-ness". From what little experience I have with the System 3 Clear Coat working with the student, it was not all that different from the 105/207 - a bit lower viscosity maybe. While both require a bit more layers for building up the coating to bury the cloth, IIRC, the Clearcoat required more layers than the 105/207 and both required more coats than with the GP resin.
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    Default Re: Epoxy paint compatibility problem?

    Quote Originally Posted by Roger Long View Post
    What do you guys thing of this stuff?

    http://www.epoxyproducts.com/marine.html

    and

    http://www.epoxyusa.com
    Haven't tried either and can't comment. Paul had offered a sample of his stuff at one point in time and I failed to take him up on it as I was too busy to sit down and try it at the time.

    Quote Originally Posted by Roger Long View Post
    Just what is the purpose of amines in epoxy anyway if the cause so many problems? It epoxy can be made to work without them, why all these problems?
    AFAIK, it is a choice in how the system is designed. Probably cost/performance balance.

    Quote Originally Posted by Roger Long View Post
    BTW I put a heater in the room with the hatch cover and it seemed to slow down the drying of the paint, I imagine because the heat is accelerating the curing of the epoxy underneath and releasing more amines. It's dry to the touch but still feels sticky instead of slippery. I expect I could still scrape it off but it feels like it's going to harden up eventually.
    Probably true about releasing amines - the stuff is still curing. How warm was the shop where you were working? 55F? 65F?

    That's one of the concerns that I have with Rod's method - that you'll get a candy shell over uncured base (the second coating) and that in the long-term it will have issues from a poor mechanical bond. Here's what one vendor mentions about cobalt drier - and they're selling the stuff :

    It is a powerful oxidation catalyst; and as a result, in coatings containing cobalt alone, the surface dries preferentially causing surface wrinkling and poor through dry in the extreme. It is therefore combined with other metals such as lead, manganese, calcium, zirconium, etc. traditionally (i.e. in conventional solids coatings) or with aluminum or lithium in modern high solids coatings.
    "Anyone who says they like portaging is either a liar or crazy."
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    Default Re: Epoxy paint compatibility problem?

    Rod--I was very happy with the progresive epoxy. I would use it again for a big project. I had that one failure which was probably my fault. I did everythigng with it: laminate, fill work, cloth application. I think it is pretty comparable to West except doesn't smell as bad and is much cheaper. If I had the time I would do some test batches using different percentages of filler to make sure there was no issue there but I used it plenty of times with all kinds of West fillers and it performed perfect. Like I said, I've also thinned it with Xylene to make a penetrating epoxy. It worked. Not as well as CPES and cure times much slower but I bet that would be true of any epoxy you are thinning.
    Chuck Thompson

    1955 18' Chris Craft Continental
    1950 30' Chris Craft Express
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    Default Re: Epoxy paint compatibility problem?

    The paint is virtually dry. It feels normal to the touch but is not quite as hard as it should be. Considering the progress over the day, I think it will harden up. If this were the part of the hatch cover I walk on, I would strip it and redo it just to be on the safe side. Since it's the part protected by the turtle cover, I'm just going to put the finish coat on it and call it done.

    It's been interesting.

    I'm going to order some non-amine epoxy for the re-tabbing I'm doing inside though. I don't want to wait two weeks to paint over it.
    Roger Long

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    Default Re: Epoxy paint compatibility problem?

    That's one of the concerns that I have with Rod's method - that you'll get a candy shell over uncured base (the second coating) and that in the long-term it will have issues from a poor mechanical bond. Here's what one vendor mentions about cobalt drier - and they're selling the stuff :
    In my experience this has never happened... Alkyd enamiels etc dry completely and usually a bit harder.

    RodB

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