Epoxy Sealant on Plywood: a cautionary tale

  • We are currently upgrading MFK. thanks! -neo
Well, I've never used pond armor, but you're right, the manufacturers do recommend that you use cement board inside your plywood (not actual cement). The problem like I said with concrete is that it's... well it's a crap material unless it's used properly. Cement board (Or Hardi-Board) is made with a special process so it doesn't crumble - and even so it can be crumbly if you're not careful.

Having never worked with pond armor, I feel a bit off saying this, but it strikes me as a crap product. It appears difficult to use, it's expensive, it's too thick to soak into anything or spread easily, too thick to use with conventional fabric reinforcements, it can't be sprayed, blah blah blah. For the same price you could use polyester or epoxy (both of which bond very well to anything remotely porous) and top coat with sweet water if you want to use a product guaranteed to be fish safe, or even just do what I've done in the past and say 'the hell with it' and not bother top coating (which has worked out fine). Having said all that, everyone who's used it seems happy with their customer support and whatnot, even when they've had significant technical difficulties getting it to work the way they want.
 
Tor-Eriik said:
I could lay out the price of the epoxy work for the 1200 gallon tank i have. 2000$ did it cost, thats why i would pick another route next time.
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Wait, you spent 2 grand on epoxy? didn't you use extra cheap OSB for the structure? This doesn't make a great deal of sense... but yes, epoxy is expensive - that's why I advocate polyester.

As for the steel - steel is expensive and heavy too, and not easy to seal, and you'd still need to seal it with LR or sweetwater when you were done.
 
I don't know, epoxy isn't THAT expensive when you consider what you are protecting as well as considering the cost of a custom made tank. I spent $140 on 1.5 gallons of epoxy + the colorant (max acr) and shipping TBH that is not that pricey. Hell a gallon of good wall paint at Home Depot now costs close to $40. Used correctly I don't know why someone would use something else, Pond Armor seems rediculous in it's price and the outcomes people have had with it, Zavlar also comes to mind as a product I wouldn't use due to it's problems with silicone, it just isn't worth saving a few bucks for. It seems as long as you do things right, and I am thinking of Joe Salvatori's 1700 gallon shark tank ( I think you could hit his tank with a mac truck and it wouldn't leak), you are no worse off than buying a custom glass/acrylic tank. Like someone else mentioned, using fiberglass, using a thinned down initial coat for bite, sanding between each coat all simple things that can help lead to success it's just taking the littel extra time and effort to do so. Again this is all just IMHO, which is all in all completely worthless since I'm a first time builder :p
 
stempy said:
I don't know, epoxy isn't THAT expensive when you consider what you are protecting as well as considering the cost of a custom made tank. I spent $140 on 1.5 gallons of epoxy + the colorant (max acr) and shipping TBH that is not that pricey. Hell a gallon of good wall paint at Home Depot now costs close to $40. Used correctly I don't know why someone would use something else, Pond Armor seems rediculous in it's price and the outcomes people have had with it, Zavlar also comes to mind as a product I wouldn't use due to it's problems with silicone, it just isn't worth saving a few bucks for. It seems as long as you do things right, and I am thinking of Joe Salvatori's 1700 gallon shark tank ( I think you could hit his tank with a mac truck and it wouldn't leak), you are no worse off than buying a custom glass/acrylic tank. Like someone else mentioned, using fiberglass, using a thinned down initial coat for bite, sanding between each coat all simple things that can help lead to success it's just taking the littel extra time and effort to do so. Again this is all just IMHO, which is all in all completely worthless since I'm a first time builder :p
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You're well researched for a first time builder - you'll be just fine! You're right, I agree, when put into context, epoxy isn't that expensive. I believe Tor-Erik did several layers of glass cloth with epoxy on a relatively huge tank, so $2k isn't that surprising. I'm about $300 into epoxy on my 200gallon reseal (same tank this thread started out with) but I've gone overboard and used way more than I needed. I still like polyester, but I am a bit biased, as I have much more experience and feel for it than epoxy. If I build another monster I will likely use polyester again, just for the fact that it's dirt cheap, can be used with chop mat (also dirt cheap), and I find it easy to work with.
 
cvermeulen said:
You're well researched for a first time builder - you'll be just fine! You're right, I agree, when put into context, epoxy isn't that expensive. I believe Tor-Erik did several layers of glass cloth with epoxy on a relatively huge tank, so $2k isn't that surprising. I'm about $300 into epoxy on my 200gallon reseal (same tank this thread started out with) but I've gone overboard and used way more than I needed. I still like polyester, but I am a bit biased, as I have much more experience and feel for it than epoxy. If I build another monster I will likely use polyester again, just for the fact that it's dirt cheap, can be used with chop mat (also dirt cheap), and I find it easy to work with.
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I have use liquid rubber and epoxy before for my 600g build and you are right, LR is crap and can't do anything to once it in use. As for epoxy I do get crack hair line like your too, but because I didn't use fiber glass cloth with it. Now with my new build I go with fiber glass cloth and polyester and yes its smell when apply but if well vent and dry up and solid, I then use gelcoat wax to for final coat and the color that I want and yes sanding is necessary if you want a smooth looking interior and hide all the fiber glass cloth. Will find out in 2 weeks if my build can hold water.
 
tbh 4mm steel is not heavy at all, and sealing the tank is a welders job :) Then you can just topcoat it.. i went with OSB yes, and there was zero $ left when i was done with this build, so i dont regret that :)

I used around 20kg`s of epoxy on the build.
 
I cant belive that epoxy will crack. I put a very thick layer (2mm) with no fiberglass on a thin glulam board an i can flex it almost like a U and it will not crack :p
 
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