Epoxy not TOTALLY 'waterproof' ??

[sdunt]

I picked up this little tidbit on another forum and now it starts to help explain some of the things that we see in boats. also keep in mind that some areas of the US, Arizona for example have basically 0 humidity. But many other areas, especially where we all like to boat have high humidity.

1.) Water and water vapor are two different things.
2.) Water is liquid and as a liquid it can not get through epoxy.

3.) Water VAPOR is a gas and it CAN PASS through epoxy -- very slowly of course.
4.) Over time water VAPOR can accumulate inside wood, then condense into liquid water.

So I little explanation of how that water got into the epoxy sealed flooring..

So, for me I am glad I went the route of leaving the bottom of the floor open so the vapor can escape that way.

 

[ondarvr]

Re: Epoxy not TOTALLY 'waterproof' ??

Water (in one form or another) can permeate virtually any surface or material, thats why nothing is really "water proof". It's just that it happens so slowly that most of the time it's never noticed.

 

[wca_tim]

Re: Epoxy not TOTALLY 'waterproof' ??

Sorry to be a pain in the ... It's even more complicated than that... Not all epoxies are the same... Epoxy refers to the type of chemistry used in the curing process... That's only part of it and actually other things make up the bulk of the material once it's cured... That being said, most of the "marine epoxies" are built to be about as waterproof as they can be for a reasonable cost. They're good, but as mentioned above, some water gets past almost anything given enough time. My understanding is that marine epoxies are generally somewhat brittle - especially after a long period of time and that they'll only hold up to soo many cycles of being stressed. I would bet that in most or all of the cases where water gets past epoxy in sufficient quantities to make wood there are cracks letting it by... imho of course

 

[jcsercsa]

Re: Epoxy not TOTALLY 'waterproof' ??

Water (in one form or another) can permeate virtually any surface or material, thats why nothing is really "water proof". It's just that it happens so slowly that most of the time it's never noticed.

I am with ondarvr on this one , I am useing epoxy on mine and I should hold up a lot longer then I plan on have the boat !!!! I hope , and a'nt resin the same way?? and dont you have a better chance of water getting into resin with it not being a full chemical bond ?? poly to poly ?? John

 

[ondarvr]

Re: Epoxy not TOTALLY 'waterproof' ??

Epoxy is better than polyester, in that it's stronger, bonds better and is more water resistant, but it's not a miracle product and the benifits get over stated at times. There will be little difference with a poly to poly bond in water resistance comparing a chemical or mechanical bond when done correctly in your type of application. I would say it's most likely the same for both products, over time stress craking or poor sealing of holes will destroy the wood by leaking long before enough water came through the laminate to rot it.

 

[Grits]

Re: Epoxy not TOTALLY 'waterproof' ??

Hello Everyone

I remember reading a test, for moisture resistance, on different finishes. If I recall, the test was related to gunstocks. The two best sealers were epoxy followed by polyurethane. The wood was sealed, weighed, submerged in water for a period of time, and weighed again.

I have seen very little epoxy used on gunstocks. I believe it is due to the cost and lack of UV resistance. Everything I have read says to protect an epoxy finish with something with a good (if there is such a thing) UV barrier.

I only have one gunstock finished with epoxy and I have to admit it is incredibly durable. It is a competition gun I have had for over twenty years and I have shot over a quarter of a million rounds though it. The finish is not as pretty as an oil or even polyurethane but it is tough. Just mtcw.

Grits

 

[reelfishin]

Re: Epoxy not TOTALLY 'waterproof' ??

Not much is totally water proof, I once saw a demonstration at a trade show on the safe use of certain cleaning chemicals. The guy had several small goldfish bowls with a fish in each one. He passed each one around so everyone could see that it was normal glass and there were no tricks being played, then he proceeded to spray each one with several different cleaners making sure not to get any in the open tops. (He was selling a bio degradable cleaner that was supposedly safe for the environment). When he took plain old window cleaner and sprayed the glass, the fish died nearly instantly, the same with about half of the cleaners he used, the only one other than what he was selling that didn't kill the fish was Simple Green mixed well diluted.
The cleaner permeated the glass nearly instantly and while the water didn't change color or anything, the fish immediately reacted to it. (I'm sure the animal rights people would love such a display these days too).

I have also heard similar warning from aquarium and pet stores about common window cleaner.

I would never have believed it if I hadn't seen it and I've seen people kill off aquarium fish doing the same thing. If glass is that porous, I can imagine that epoxy or any resin would be too. Fiberglass can also absorb water over time.