help. which silicone ge 1200 or dow 732

[Chicago]

ok ..i now it has been asked before ..but i have to repair some bracing. the manufacturer used ge 1200. the center brace is giving out. so i have my glass guys coming to do some repairs. the tank has three cross braces with perminter bracing in between each of these.. after the re silicone of the cross brasses we are going to put a 111 x 3 x 1/2 starphire across the front of and on top off the perimiter and crosses braces. so that they are silicone together.. the thought is if the cross braces start to fail where they meet the front then the perimiter brace since it will now be attached to the cross will add strength..

so here is question.. tank was made using ge 1200.. but i am concerned that it is not a good product. mixed reviews.. there was a post somewhere here that said not to use it as the rep of ge said not good for under water use. that seem right. i know silicone will adhere to silicone if cleaned up really good. i do not plan on removing the perimiter bracing which is not at issue.. so my gut says stay with the ge 1200.

but i have heard good things about the dow as that is what glass cages uses.

thanks..

 

[ycrazyy]

Best silicone to use is the Momentive RTV108 silicone. It is by far the strongest and is also FDA approved for food use so it is reef safe. Run by your local Grainger and pick up a couple of tubes, item #4UH12

 

[Reefbox]

Thanks for info. I'm going to give that momentive rtv108 a try. Does it come in black?

 

[Chicago]

thank you for the info. so lets talk.. why is this better than ge 1201 or dow 732.

stronger

fda approved i understand.. but the 1201 and the dow do not have issues with reef tanks.

will it bond to plastic rims? will it bond to other silicones.
thanks

 

[uncleof6]

In the first thread concerning this tank, several quite directly advised to replace the tank. This is still the best scenario to be thinking about.

You have a pressure related issue with the front panel of the tank, probably because it is laminated glass, and does not have the strength that a solid pane of glass would. Whether it is a crack, or delamination is not the issue, the fact is it is failing.

Next due to the pressure in the tank, the bracing is coming apart, which is more than likely the cause of the front pane failure. The cause could be the silicone degrading in salt water -- which all silicone does do eventually, or due to the fact that the laminated front pane is not as strong as an equivalent thickness solid glass pane. Really, at this point that does not matter either.

What matters, is you are trying at this point-- to polish a "T" (cow pie.) "Myth Busters" has proven this is possible, but in the end all you have is a polished "T."

To make this repair correctly, you are going to have to drain the tank, and rebuild it-- or junk it for a new one. Period. This tank is suffering structural failure, not cosmetic damage of no consequence, that resin and DC732 can cover up. (DC732 is a sealant not an adhesive.)

To fix the top bracing the pressure needs to be removed (drain the tank) to hide, whatever the problem with the front panel is (I don't really think it can be repaired suitable to hold against the water pressure), the pressure needs to be removed (drain the tank.) Cleaning up the old silicone, siliconing over it, is not going to hold. All traces of the old silicone need to be removed. We are talking glass and silicone under pressure, not just a couple pieces of glass being held together, like a windshield or display case.

Dow Corning is a sealant not an adhesive (its adhesion properties are low--not published) Its tensile strength is 333.6 psi. SCS1200 has a tensile strength of 470 psi, and adhesion of 40 psi. Momentive RTV108 tensile strength of 400 psi, and adhesion of 40 psi. I would not put together anything larger than a 30 gallon tank with 732.

I put my money where my mouth is with this stuff, and if you asked me to come in and fix this thing as you are proposing, and you insisted on it, I would walk away. You could not pay me enough. Tanks have a life span, yours is expired.

FWIW,

Jim

 

[Chicago]

yep.. i hear you guys loud and clear. the front failed because the silicone failed. it was structurally sound for over five years. the problem i blame my self partially. i should have watched and cleaned the over flows better. the water level was left too high as result of bad cleaning on the over flow and coraline algea formed and i think i also messed up when cleaning the front. razor blade under the silicone and off it went .. started to go bad. so i am going to give the all american try and clamp and silicone. I realize this is a calculated bet. I under stand believe. 30 plus years of doing this. 20 years with large tanks. i have moved and set them up. just never buildt them.. thus all the questions.. if you asked me how to move them.. i could give you great advise... even taught piano movers how to do it..

so scs1200 or rtv108.. rtv108 is actually ge 1200?

 

[uncleof6]

Two different products. RTV108 is better suited to the task at hand, and is used for tank building more than any other.

Proceed at own risk

Jim

 

[Chicago]

by the way.. interesting.. dow 732 is what glass cages is using.. i did have some converstaions with them.. nice guy.. spent 20 or so min talking with me on the phone..

 

[Chicago]

uncle.... thanks for the info.... i just hope i dont get a post from you that says.... told you so.... i would in response say.. i saw it coming... thanks though for the input. will be getting rtv... i have three tubes of 1200....sounds like i should not use and mix products.. i assume the rtv adheres to plastic... ect..

on side note. i could maybe i should build a 2x4 in front of the glass as support.. and make a shelf... argg.. ok i still have a sense of humor.. lets see how long it lasts..

thanks

 

[uncleof6]

by the way.. interesting.. dow 732 is what glass cages is using.. i did have some converstaions with them.. nice guy.. spent 20 or so min talking with me on the phone..

Ask GC for an MSDS for the silicone they use on their large tanks. I did this with Aqueon, they said they do not use GE silicone, turned out they were using Momentive RTV100 series (formerly GE.) Publicly they claim to be using their branded silicone to build tanks, (on the label) buzzzzzzzzzzzzzzzzz wrong.

I won't buy a DC tank anyway....why would I? But if they are using 732, well that is just another reason.

Jim

 

[Chicago]

sounds like i am off to grainger.. rtv 108,,,,

 

[Chicago]

what do yoiu use to clean glass before silicone. ... thought to use.. vinegar. or actehoydey?

 

[uncleof6]

Depends on what the circumstance is. New glass, alcohol. Prior siliconed glass-- razor blades (many), steel wool and acetone--and a lot of elbow grease. Glass needs to be "squeaky" clean.

Jim

 

[Chicago]

Ok left grainger. On line says momentive rtv 108. But warehouse will call pick up comes up with ge series rtv 100 series on main label and on the bottom of it in small black letters says. Rtv108. I assume momentive relabels ge? Says general purpose in small black letters on bottom rtv108 trans 06mo38. Do I have the right stuff. Just parinoid ??

 

[fishkeeper00]

check out dow 999a

 

[Chicago]

ok.. now i get it.. 108 is the clear.. little internet search.. but that of course only resulted in more interesting threads with silicone opinion fights.. i have the ge rtv 108 and tubes of the scs1200. looks like both are good products.. scs describes it self as capable of bonding to plastic.. website does not mention rtv bonding to plastic.. like the rim on tanks..

looks lilke tensile strength for scs 1200 is 470.. rtv 400.. but interesting 1200 has warning about being used underwater.. lawsuits???

 

[uncleof6]

Momentive Performance Materials acquired GE silicones in 2006, so GE no longer makes silicone. Momentive RTV108 and GE RTV108 are the same product, just different packaging. The packaging has already been changed, so if your tubes say GE, it may be old stock.

Jim

 

[Doug864]

ok.. now i get it.. 108 is the clear.. little internet search.. but that of course only resulted in more interesting threads with silicone opinion fights.. i have the ge rtv 108 and tubes of the scs1200. looks like both are good products.. scs describes it self as capable of bonding to plastic.. website does not mention rtv bonding to plastic.. like the rim on tanks..

looks lilke tensile strength for scs 1200 is 470.. rtv 400.. but interesting 1200 has warning about being used underwater.. lawsuits???

Interesting stuff. I'm in the process of building a large tank and silicone was a big concern of mine like everyone else. I talked to 2 representatives at momentive and one said scs1200 was the best hands down and that many builders use that. The other rep was from the industrial side of momentive and he said both types are almost exactly alike except one (rtv108) is industrial and the other(scs1200) is commercial. The main difference was tensile strength- 470 verse 400 as stated above. There is one phrase about small bubbles in scs1200 in their product description. I asked both reps about that and both said it was mis-information so to speak. Don't know if this helps at all but it might. I think there is more to diy tanks than just the type of silicone. Cleanliness, proper joint gaps, tooling, and cure times are maybe? more important. Just my opinion.
Regards,
Doug

 

[Chicago]

Did the rep say if either bonds better to old silicone assuming proper prep. Any mention of bonding to plastic. Scs 12000 mentions it. Now are the ge rtv tubes I just got out of date. I know there is a certian shelf life .., wondering if o6. Means 2006

 

[Acrylics]

If it's that old or with the old packaging, I'd return it for a new tube. All silicones should have a mfr date on them and IME 6 months is about it for shelf life.

I don't know if the 108 is a neutral cure or acetoxy cure, but for plastics - neutral cures are better, hence in the plastics world we generally use 1200 or DC795. Both offer good adhesion to plastics, can't say anything about the 108 as I've never used it.

HTH,
James