Two part epoxy not curing

[Seahorse24]

My son and I applied a barrier coat of CM-15 Two part epoxy to the bottom of our sailboat. The surface was clean, dry, sanded with 80 grit prior to the application. We followed the directions on the product as to mixing, temperature, humidity, dew point, etc.

Sixty percent of the bottom has not cured after 4 days. We contacted the supplier who stopped communicating with us after we sent him a photo of the mixing directions on the can. He first told us we should have hand mixed it instead of using a drill and jiffy mixer. The instructions on the can clearly state Do Not Hand Mix. Use a drill and jiffy mixer to mix thoroughly.

We now have a sticky bottom that will never dry. I read on-line to use de-natured alcohol to remove and start over. The denatured alcohol removes some of the colored pigment, but what is left us still sticky to the touch.

The product cured in the paint trays, on the rudder and on 40 percent of the hull. The remainder in the can ( 1/2 gallon ) also cured hard.

My son and I have used two-part epoxies on power boats since 2002 without any problems, but this is the first time we used CM-15. We normally use the no-blush two part epoxy, but used the CM-15 because it is for hulls that can flex.

What should we do? Has anyone had this problem? How do we get the stuff off so we can start over?

 

[Rick Templeton]

This is a real long shot, but, I might try to apply the o2 barrier that you use with fiberglass and see if blocking the product from oxygen might help it set ? As stated, Kinda a long shot but sounds like you might need a hail Mary. (Try on a small strip first)

Hope you get it figured out! Let us know what happens.

 

[Allan12210]

This is a real long shot, but, I might try to apply the o2 barrier that you use with fiberglass and see if blocking the product from oxygen might help it set ? As stated, Kinda a long shot but sounds like you might need a hail Mary. (Try on a small strip first)

Hope you get it figured out! Let us know what happens.

Epoxy is not oxygen dependent for curing like polyester (or rather requires lack of oxygen). It sounds like the coating was chemically poisoned some how on those specific areas of the hull. If the rest cured in the can and the tray then that resin mix was ok. Denatured alcohol won't remove it. That is too much like water. After scraping as much as you can mechanically, you need a stronger solvent like acetone.

Did you mix more than one batch? If so, could there have been some confusion in the ratios? This is very weird indeed.

 

[Ralph Johnstone]

The product cured in the paint trays, on the rudder and on 40 percent of the hull. The remainder in the can ( 1/2 gallon ) also cured hard.

With the larger volumes curing, it sounds as if it was the heat of curing which cured the epoxy. The thinner areas did not have the volume and hence not the heat and were borderline at best.

All this sounds good but it doesn't help you any.

Can you run a test on a small area to see if high heat (up to 120 deg. F as they suggest) will help in curing ? If it does, don't ask me how to heat the entire hull.

The instructions state that the epoxy can be thinned up to 20% for conventional spraying ............ but don't say with what ? ? ? ? My epoxy experience is with System Three Epoxy (not a barrier) and they specify lacquer thinner as the thinner. It may be worth a try lacquer thinner if all else fails.

Good luck on this. I did an epoxy barrier coat using Interlux Interprotect 2000 on my boat a number of years back and it's a big investment in both time and money. Having something like this happen (along with an idiot vendor) is sure to be one of life's biggest pi$$ offs.

 

[Rick Templeton]

Alan and Ralph,
I stand corrected. If that's the case can you apply a light coat of the activator to set it off then sand?

 

[Seahorse24]

Thanks everyone for your responses. If a coat of activator would cure what is sticky, that would be the easiest solution.

If that doesn't work, sounds like scraping off the non-cured layer is my next best option.

Tomorrow, I will do a small test area with a light coat of activator and see what happens.

 

[Allan12210]

Thanks everyone for your responses. If a coat of activator would cure what is sticky, that would be the easiest solution.

If that doesn't work, sounds like scraping off the non-cured layer is my next best option.

Tomorrow, I will do a small test area with a light coat of activator and see what happens.

Unfortunately it probably won't work. The components have to be thoroughly mixed and the reaction will take place in the bulk. Putting one component on top may cause some reaction to occur at the interface, but the depth may still be un-reacted and come off eventually. The reaction mechanism is different from polyester chemistry that uses a peroxide activator that isn't really part of the final cured matrix. Try a little area, but you might always wonder if the adhesion in that area might be compromised.

A second experiment might be to mix a small amount properly and put that over the sticky area. If the ratios are forgiving, it might stimulate the cure in the existing area along with the proper mix on top.

Something strange must have happened as once mixed, a batch usually exhibits consistent behavior.

Let us know how it goes.

 

[Johnb]

I would try warming an area with a hair dryer (NOT a heat gun) and see if that does any good

 

[Capt jgw]

I've never used CM15, but all the different brands I have used, if mixed correctly it will eventually cure, no matter what. I've even had it kick off in the freezer when I tried to save some to use the next day. The fact that some of it cured properly doesn't mean it was all mixed correctly. There still could have been some unmixed components floating in the matrix.
I've never tried power mixers, my drill is to hand stir for three to five minutes in one pot, scraping all sides and corners, then transfer to another pot and stir for another two or three minutes. Sometimes the first pot ends up with uncured resin in the corners, even after five minutes of stirring. Can't imagine why the manufacturer would specify power mixing. IMO, if the manufacturers stopped talking to you that's an admission of guilt. If they told you you did it wrong and you're on your own is one thing, but ignoring you is another. Bad costumer service at the least.

 

[woodster]

i personally like west system epoxy just because it comes in a pumping mixing dispensers...1 to 1 mix on the pump and it also blends to one transparent color when mixed unlike the 12 drops you have to count out of a tooth paste tube to so many ounces of resin it may cost more but i have never had a failure with that stuff ....as for your problem try heat lamps ...and if that does not do it ...scrape it off and wash it down like Ralph said

 

[rgranger]

I would try warming an area with a hair dryer (NOT a heat gun) and see if that does any good

I was going to say the same thing... and if that don't work... try removing it with a paper towel or sponge soaked in vinegar. Epoxy is a polyamide (base) and acetone is an acid... so it not only acts as a solvent but any uncured amide linkages will be ionized and made water soluble. It does not need to be expensive vinegar... get the cheapest stuff you can find in bulk. The vinegar will only work on uncured epoxy so your other areas will be fine. I've used vinegar to get uncured epoxy off of my rollers... it works very well and it is a lot safer to use than organic solvents.

 

[Seahorse24]

Update on epoxy problem

I tried de-natured alcohol. Only a little black pigment dame off on the rags. Then I tried acetone. Same thing. Only a little black pigment came off, but still sticky to the touch.

Next I got a paint scraper and tried scraping off the black. A thin layer would come off, but really hard work. Mostly looked like a thin layer of pigment, like on the rags.

By this time, my son arrived at 9:00 AM. I told him what I had tried and the suggestions I had received on this site. We discussed our options and decided to mix a small batch of the CM-15 from a new gallon can and apply it over a test area, hoping the new layer would re-activate the first coat that would not dry.

The first thing we noticed when we opened the second gallon, which Is an ivory color, was the ivory colored gallon had a totally different consistency than the black gallon we had mixed up and applied the first coat which would would not dry. The black gallon had a much thinner consistency. The ivory gallon is thicker and rolls on a thicker coating.

We mixed up a pint and applied it to our test area. Within five hours at an outside temperature of 93 degrees, the ivory was dry to the touch. It appeared to be well bonded to the hull over what was previously a sticky mess.

I am now convinced the gallon of black was a defective gallon, and our mixing and application had nothing to do with the sticky non-drying mess.

Based on our test area, it appears we can apply the ivory over the uncurred layer of black and it will bond to it and dry to a hard finish. We are assuming the new layer re-starts the drying process fir the uncurred layer. If I can't scrap off any ivory tomorrow morning, I am going to apply a coat of ivory to the rest of the bottom.

Thanks again for all of the suggestions.

 

[Allan12210]

Well that's good news. Smart move to choose a different color so you could see the differences.

I'm thinking that the reason the acetone didn't remove the sticky black material was that it was already partially cured, starting to render it insoluble as cross linking progresses. Maybe in another month it would be done. I'm still at a loss why it would do that, especially since some of the batch seemed to cure correctly. Do you have any of the un-mixed black left (including both components). You could do a small experiment in a Dixie cup of the black with new hardener and then some old (from the black) hardener and the ivory. Spread them out real thin on a board and see if one does or doesn't cure as fast as the other. That's what a chemist (like me) would try. Or, as a justifiably irate customer send the rest back to the manufacturer and tell them to give you your money back.

I hope it all works out for you.

 

[Seahorse24]

Well that's good news. Smart move to choose a different color so you could see the differences.

I'm thinking that the reason the acetone didn't remove the sticky black material was that it was already partially cured, starting to render it insoluble as cross linking progresses. Maybe in another month it would be done. I'm still at a loss why it would do that, especially since some of the batch seemed to cure correctly. Do you have any of the un-mixed black left (including both components). You could do a small experiment in a Dixie cup of the black with new hardener and then some old (from the black) hardener and the ivory. Spread them out real thin on a board and see if one does or doesn't cure as fast as the other. That's what a chemist (like me) would try. Or, as a justifiably irate customer send the rest back to the manufacturer and tell them to give you your money back.

I hope it all works out for you.

Thank you, Allen. We mixed up the first gallon completely. We used half and the other half cured in the can so it is hard as a rock. In past years, we had purchased three gallons of the No-Blush two part epoxy from the same manufacturer and never had a problem. This is the first time we had tried their CM-15 product. I will never order any of the CM-15 product again, but the No-Blush appears to be fine, if you don't need the flex option.

I have since found other two part epoxy barrier coats that work on a hull that can flex. One has good reviews, available from multiple sources, and is $20.00 per gallon cheaper than the CM-15.

As a side note, while my son and we're waiting to see if the epoxy dried, we built a bracket to support the 6 HP outboard. I'll post photos of the bracket in a day or two.

 

[Seahorse24]

Final Update on epoxy barrier coat status

The test area appeared well bonded this morning so we mixed another batch of the two-part epoxy barrier coat and started applying it at 1:30 PM. It took two of us us thirty-five minutes to cover the entire bottom. Dried to the touch in five hours. Outdoor temperature was 90 degrees.

I will apply another coat tomorrow and should be able to finish the bottom painting by the end of the week.

What appeared to be a disaster earlier in the week with the first epoxy coat not curing may now be under control. The subsequent layer did one of two things. It either restarted the curing process of the first layer and both layers chemically bonded or the second layer bonded to the sticky mess that did not cure and encapsulated it. I guess we won't know the long term results until we place the boat in the water and start sailing her.

I want to thank those who commented, offered suggestions, or just wished us luck. Hopefully, the bottom will be good to go by the end of the week.