Using silicone or other flexible sealant on acrylic

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Chaz88

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Feb 21, 2010
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I originally posted this in the silicone sticky but I do not think it gets checked much. Thought I might get more action with a new thread. After doing some research I found that 3m 5200 is poly based. Would be interested in hearing about anything that can be taken down later but will last long term before that. Long term being along the lines of glass and silicone, not just a year or two.

3m 5200 marine !!! all the way i used it to build two 400 + gallon tank last year and i recently tried to make some mods on the acrylic window and that stuff is never coming off !! and algea is covering every bit of it so it shouldnt have any anti mold chemicals.
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If anyone has anymore experience with silicone on acrylic I would like to hear about it. For a long time conventional wisdom was that it will not stick to acrylic long term. I am thinking about building an acrylic tank using glass methods. I will eventually need to take it down and move it. The setup I have in mind would be impossible to move if it was welded together as normal with acrylic. I have not looked into silicone for a long time. Is there stuff out now that would work long term?
 
wednesday13

wednesday13

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Mar 2, 2008
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3m5200 on acrylic using typical glass building techniques will explode the first time u fill it. It bearly adheres enough for a single window on a plywood type build when used as a gasket. Silicone is for glass....solvents/epoxies are for acrylic, one will not work on the other... Weld-on #4 is used for constructing thin acrylic, it is a solvent that melts the acrylic together. Weld-on #40 or #42 are two part epoxies used to fuse thicker guage acrylic. In my younger days...very younger lol... i built a small metal frame tank lined with acrylic sealed with silicone as u propose. First time it lasted for a month. Second time i ran 1-2" beads of silicone and it made it 6-8 months. You stand no chance at sealing acrylic with silicone without a structure to hold the acrylic itself. Even then it certainly wont last forever. You can tear down a glass tank piece by piece, or even a plywood/fiberglass one. Theres a collapasable plywood build in the articles section of the forum u should check out for ideas. Its possible to build 4 walls, bolt em together, then silicone the seams as u would a glass tank.

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FishDog

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As mentioned no way it would work. The only way you would have a chance is to buy acrylic twice as thick as you would need and build some kind of frame around bottom and top like angle iron to hold together. That would be way more expensive then it is worth. Silicone of any kind can barely seal acylic much less provide structural support. You would need like 3/4" just to go 18 to 20" tall as anything taller would probably bow the acrylic and break the seal. You could drill and use small 1/8" self tapping machine screws and screw it together then seal it but it will eventually crack over time.

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Chaz88

Gambusia
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Feb 21, 2010
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I have built plywood tanks before. I know the conventional wisdom regarding acrylic and silicone type sealants. I have not looked into it for a long time. But things change and thought there might be something new out I was not aware of. Not necessarily silicone because it is unlikely to ever be formulated in a way that can make a good bond with acrylic. I never say never because construction material advancements have come a long way and we can do things now that were not even thought of when I got my first tank, that I cared for on my own, 35+ years ago.
 
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