Barrier Coat and Paint problem

[Jeff Bacon]

Hi All:My boat is going into it's third season, and I have not been able to get bottom paint to stick to the bottom........ it comes off in sheets during the season.Lake Erie sailingVC 17 paintInterlux is going to pick up the tab for removing the VC 17, sanding, and application of a barrier coat, then Micron Extra. I plan to be back in salt water in the next couple of years, so this might be a fortuitous situation, as I understand that VC 17 does not like salt water.However, are there any drawbacks to the barrier coat. Hunter has given their blessing regarding the sanding, but, does barrier coating cause any future maintenance problems ? Is there any annual maintenance I need to be concerned with ? Or, if I want to switch paints as I get to warmer weather and water, will there be any considerations ?Thanks for any help........ Jeff

 

[Gord May]

no problem

Just make certain that the epoxy barrier coat has a chance to 'cure' prior to overcoating /w anti-fouling and relaunch.See:Interprotect Bulletin 900Fhttp://www.yachtpaint.com/Images/15_6819.pdfAkzo Nobel (Interlux) Home: http://www.yachtpaint.com/

 

[Ed Schenck]

Like iron

You cannot hurt barrier-coat(properly applied), it is a really hard epoxy. It sounds like they never got the mold release out of your gelcoat Jeff. That might explain the VC17 peeling. I don't know if you would have to worry about preparation for the barrier-coat. And it will take any kind of paint.Most will advise you to use a good ablative for salt water. But I like modified-epoxy, specifically Trinidad SR(Petit). I know it is more work due to sanding before the spring coat. But it sure is harder and faster. And I could get three seasons on Lake Erie but have been putting on a light coat every other.

 

[Gerry, GMJ Marine]

Bottom paint problem

Jeff, As Ed said, I also think that the mold release was not thoroughly if at all removed prior to bottom painting. Sanding does not remove it so make sure that whoever reworks your bottom gives it at least two thorough washings with a good dewaxing solvent after the VC-17 is removed. The two rag method is really the only way to correctly remove the mold release. One rag to wash and the other to wipe before the solvent dries. Do a 2 ft. square area at a time, flip the rag every square, and change to clean rags frequently. I use Inter-Protect 2000 all the time and have never had a problem with it holding paint. Be sure to follow the application specs. and there shouldn't be any problems. Good luck.

 

[John Dawson]

Gord, are you sure?

If we are talking about Interprotect, which was your reference, bottom paint will definitely have trouble sticking to it. The link to Interlux specifies the 'thumbprint' test, in which the barrier is tested to see if its partially cured - tacky enough to leave a thumbprint but hard enough to not come off on the thumb. By painting the first layer of bottompaint into the soft pre-cured barriercoat, more layers will have a base to grip. If you let it fully cure alone, you will have to sand it to give paint a hold, and sacrifice some thickness in the process. Either that or use the 'No Sand Primer' as an intermediary.The main problem with barriers is that they are not done under ideal conditions. Either the owner does not have the patience to dry and prep the hull properly, or the job is done under wrong weather or temperature conditions. For these reasons there is a trend away from amateur jobs toward professionals doing it under controlled conditions. If you are careful and patient, its very easy to apply yourself, and is expected to last 7 to ? years.For those who can't wait and have plenty of money, they can go to a center with the technology to dry and rebake the hull, a process developed in England.There is no maintenance unless a good bond is not achieved, in which case the coat will break off, usually in small 'boilerplates'. With hard bottom paints you have to be careful not to sand into the 4-5 layers or 10mil thickness. With ablatives, this isn't going to be a problem.

 

[r.w.landau]

Stay with the product line you choose..

If you stay with Interlux, the produce labeling will take you from one to another. If you chose VC products, they will also lead through.Problem with barrier coat. You need to allow enough time to cure but you can't go over the time to overcoat unless you sand. My choice is overcoat before the sanding time limit. Once you over coat, the time of recoat is the antifoul time not the barrier coat time. Antifoul is another ballgame but again stay with similar product line and the instructions will lead you through. As far as epoxy vs. ablative: I love ablative paint. Yes you have to remove the boat from the water once in a while to recoat (as with epoxy). The plus is that the sanding is minimal with the ablative. The epoxy builds up and builds up until major chunks of paint falls off making the bottom look cancerous. AT THIS POINT COMPLETE SANDING IS A MUST AND IT IS NOT EASY NOR CHEAP.The barrier is a great thing. It does need to be overcoated because it has no UV resistance.r.w.landau

 

[John Dawson]

time of recoat

Since we are talking Micron Extra, there is no antifoul time, right?

 

[Gord May]

Barrier THEN Anti-fouling

John Dawson makes some good points. Am I sure? It’s hard to be certain, when your opinion seems to be at variance with the manufacturer’s instructions. I’m not a coatings expert, and perhaps my reasoning doesn’t hold water , but here it is:It usually takes 4-5 coats of epoxy to achieve a dry-film build-up of 10 microns (recommended minimum). I use the “thumbprint test” to determine the minimum time between coats of (unsanded) epoxy. “Wet over tacky” provides the best interlayer bond, and does not require sanding between coats of barrier.I see the barrier coat and the anti-fouling as two separate systems, in which I place the utmost importance on the effectiveness of the epoxy as a permanent barrier coat. This is why I prefer to see this important treatment fully cured, prior to overcoating with anti-fouling. Of course, this requires a final sanding, cleaning, and primer coat application, prior to anti-fouling. Although a lot more work, I believe it’s worth the effort. Essentially, I'm advising a Barrier Coat, THEN an anti-fouling - not a barrier AND anti-fouling.Notwithstanding, you should know that allowing a full cure on the barrier coat will only result in a mechanical secondary bond between the barrier and the anti-fouling. I’ve found this to be more than adequate. Interlux does NOT require a full cure, merely suggesting an “overnight”. See also WEST SYSTEMS “Technical Manual” #002-950:http://www.boater.com/repinfo/westsys/west1.htmlI neglected, but others have emphasized, the unqualified importance of starting with a clean, wax-free surface. And remember, free advice is often worth less than what you paid for it.I've been wrong before ...FWIW,Gord

 

[Wanderer138]

My experience with barrier coat and VC17

I had really good results with Interprotect 1000, Epiglass and VC17. As several people already pointed out, there are several crucial steps that must be followed.1) the hull must dry out properly. My boat was out of the water for about three months in the dry season before even attempting blister repairs. That took two more months. By the time I was ready to barrier coat, the boat had been out of the water almost six months.2) the mold release agent must be properly removed with acetone (nuff said)3) when applying the barrier coat, recoat when tacky (thumbprint test). If you let the epoxy cure hard, you have to wash it clean (soap and water, followed by acetone or methanol) to remove the amine blush, THEN sand to give the surface some "tooth" for the next coat to grip.4) After five coats of epoxy, I applied two coats of VC-Tar (coal-tar epoxy) primer and sanded lightly before applying the VC17.That was three years ago and there is no peeling whatsoever. In the process I learned that acetone or methanol will dissolve VC17, so you don't have to sand it off. If you used VC-Tar and decide to sand, go lightly, VC-Tar is black, so you should be able to tell right away if you're starting to sand through it.VC17 is made by Interlux. I included a link below to their antifouling product listing. There is a link on that page to their product compatibility chart, It used to be on-line as an HTML document, but now you have to download it as a .pdf file. Good luck and buy LOTS of disposable gloves and brushes!PeterH23 "Raven"

 

[John Dawson]

Just one detail, Gord

Letting the barrier cure fully and then sanding is perfectly acceptable procedure, but...Interlux estimates four coats will make a 10 mil thickness. If thats what is done, and then the last coat is scratched up (sanded), my concern is that you wind up with less than the minimum recommended thickness. Using your method, it seems to me an extra coat should be applied, and perhaps more when sanding for race smoothness.

 

[Gord May]

two details

John Dawson is right, “some” epoxy will be removed in the final sanding of the Barrier Coat. As you’re only cutting some tooth for the anti-fouling adhesion, it won’t be much. Perfectionists & Racers note: Any sags and runs that occur on earlier coats (epoxy) will show through subsequent coats, so must be sanded down before overcoating.Peter Suah noted that the hull must be DRY prior to starting the Barrier Coating. This is just as important in applying a barrier coat to an un-blistered hull. After dewaxing and cleaning the hull must be thoroughly dried out.