Gasket Material For Isolation

[Manateeman]

Greetings. Looking for comments on the best method to isolate a 316 stainless casting to be bolted to a 5000 and in one case 6061 series aluminum plate. The gasket material can be coated with polyurethane (5200) on both sides. Non pressure application but the edge might have occasionally and minimal contact with oil, diesel or salt water.
We have considered thin sheets of EPDM, FKM, or glass/epoxy . Not sure which would be best or are there others?
The surfaces are flat. Gasket thickness need only be 1/16 inch so just thin sheeting. It would be desirable to be able to rough up the surfaces to assist the polyurethane bond. We are not certain but think any black rubber should not be used against the aluminum. True?
The bolts will be isolated by nylon washers and tube. Threads by Tef-Gel.
Thank you in advance for all replies
The manatee crew.

[Sailmonkey]

I would use gpo3 or g10 with a coating of polyurethane on both sides to prevent water migration.

Only real downside to these two would be a lack of UV stability if that’s a problem.

[Jammer]

You can get 1/16" silicone sheet from many sources (amazon, McMaster-Carr, etc) that works well for that sort of thing and is inexpensive. If you're bolting the item in place there's no need for adhesive, and of course it won't stick to the silicone sheet anyway. Silicone is resistant to water and oil so you're covered there.


EPDM isn't really oil resistant and FKM is expensive for the application and produces extraordinarily toxic smoke in the event of a fire.



Use locking nuts on the bolts.

[dfelsent]

FYI Selden uses isolation and Monel rivets.

[bradfordharley]

I use this for isolation. You can apply glue to the backside. I would use 4000 or butyl over 5200.
https://www.homedepot.com/p/2-in-x-50-ft-20-Mil-Pipe-Wrap-Tape-53550/100179778#overlay

[Russ]

Micarta is the recommend spacer on steel boats between steel and a dissimilar metal. Russ

[Shoalbay]

Celeron AKA Tufnol AKA Haysite.

I also used plastic cut from oil containers.

[wrwakefield]

Duralac is commonly used for isolation in such use cases, but does not make a sealing gasket…

In case this helps.

Cheers! Bill

[philcun50]

Duralac just seems to work.

[qwert]

How about mylar film I have used it for years for templates. Its so cheap I buy it by the kilo. Mylar is the same chemical as polyester which lasts really well as sailcloth. It has been used for decades as an insulator in electric motors etc.
It comes as a milky coloured stiff film. Thickness is measured to the nearest thou and comes in a variety of thicknesses. It can be cut with scissors and can be sanded if you wish. Available from electrical wholesalers. I use it on mast fittings etc.

[Manateeman]

Hi. We have rolls of clear Mylar and we are testing how well 5200 will stick.
Silicon sheeting is out but there seems to be a Fel-Pro product for aluminum water pumps which might work perfectly.
Some testing ahead.
Thanks for all replies.
The manatee crew.