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treeman · 23-09-2009, 13:36

I am building some small 316/316L stainless steel enclosures that will house underwater closed circuit cameras. They have 38mm diameter round openings where a 42mm diameter disc/glass lens will be bonded from the backside directly to the 316 stainless housing. The lens will be flat as will the stainless steel. The housings will be submerged in ocean water to about 3-4 feet depth for extended periods of time so it needs to be waterproof.

I have used some standard two part Loc-tite epoxy for this and it actually works well (no leaks) but I am concerned about long term use if the epoxy will break down over time. Is there some type of adhesive that is best suited for this?

Thanks for any leads or ideas!

**noelex 77** · 23-09-2009, 13:56

Epoxy is very rigid and you may get problems with the different temp/expansion coefficients of the materials, particularly given the sudden temp changes associated with water immersion.
3m 5200 would be my first choice (providing it doesn't need dismantling later).

treeman · 23-09-2009, 14:02

Thanks for the reply. I would definetly prefer a more permanent solution and have no reason to disassemble the glass from the stainless. I did think about 5200 but I have read 5200 is not compatible with stainless steel? I sent an email to 3m to see what they say.

Will 5200 bond to smooth surfaces such as glass?

Thanks for any more input.

**Cheechako** · 23-09-2009, 14:15

Silicone may do as well as anything. Silicone is used in dive masks and aquariums...

**noelex 77** · 23-09-2009, 14:40

Quote:

Originally Posted by treeman

Thanks for the reply. I would definetly prefer a more permanent solution and have no reason to disassemble the glass from the stainless. I did think about 5200 but I have read 5200 is not compatible with stainless steel? I sent an email to 3m to see what they say.

Will 5200 bond to smooth surfaces such as glass?

Thanks for any more input.

The short answer is I really don't know. Sending an email to 3M is a good idea. The technical departments are a good knowledge base. It may also e worth looking up Sikaflex. Their web page has detailed aplication data for their products try Sikaflex 291.
You may find it difficult to find a manufacturer that will endorse their product for your application. Stainless steel forms an oxide layer that is very difficult to bond. On the bright side you have an application that does not require great strength, with only a small pressure differential an a relativly large bonding area.
Yacht transducers (about 4 feet below the waterline ) in SS would be bonded to Fiberglass, Aluminium or Steel typically with Sikaflex 291 (but manly because 5200 would make them impossible to remove), there is a mecanicanical connection as well, but if they leak the yacht typically sinks.

Mike156 · 23-09-2009, 14:41

Locktite!

No, not thread locker, but the company that makes Locktite.

Henkel North America - Home

My company makes aircraft fuselage panels from glued together sheets of (.063) metal and plastics. Henkel engineers work closely with us on using and applying adhesives.

Go to the above web site, click on technical support, then aerospace, and give them a call.

They have hundreds of products that you never see in the consumer marketplace.

Sounds like a fun project!

Mike

treeman · 23-09-2009, 15:19

Noelex, since there won't be a mechanical connection in my application perhaps I am better off going with the 5200 over the Sikaflex. Maybe I am over thinking this. The cameras are relatively inexpensive and the worst a leak would cause in this case is damage to the camera. I think something like 5200 might be better than the epoxy I am currently using being that 5200 is at least designed for underwater use.

Mike156, I actually did contact Henkel already but my message went to the consumer division and they said they could not recommend any of their products for my application. They said for me to try Loctite and their industrial division so I sent them an email. Let's see what they say.

**Cheechako** · 23-09-2009, 16:15

almost any sealant would work in your application. maybe google underwater camera housings, people made their own for years. I would bet they use silicone.... The dive shop used silicone to bed my bifocals in my mask....Bond the glass disc to the OUTSiDE.

treeman · 24-09-2009, 09:01

Thanks again for all the replies. I did get a response back from 3m and they say that 5200 does in fact bond to stainless steel with a "sheer" strength of 352psi. I am assuming this will be more than adequate for my application?

Guess I should have asked if 5200 bonds to glass as well and at what strength because I just read the datasheet and it says not to use 5200 for glass that is not mechanically fastened BUT I have read/heard of folks using it on glass and that it is next to impossible to remove.

Has anyone used 5200 with glass and if so how strong was the bond?

**David M** · 24-09-2009, 10:02

Right now I have a vertical glass window being held in place purely with 5200. Its been there for at least 10 years now. There have been no problems. I would imagine 3M is saying not to do this for liability reasons..they want to see you using a mechanical fastener as well in order to protect themselves in our litigious society.

treeman · 24-09-2009, 10:14

David, that is GREAT news. I had thought about the same issue as you mention in that the reason they specify "windows" is for liability reasons. Obviously this isn't an issue in my case at all. Ok, looks like I will be going with 5200.

Thanks again to all you guys that chimed in...VERY much appreciated!

treeman · 24-09-2009, 12:25

David, quick follow up question...did you rough up the glass at all where you applied the 5200 or was the glass totally smooth and just clean with acetone or similar and put it together? Also, I thought 5200 was UV sensitive...I assume in your application that it is getting hit by some UV?