RTV and corrosion

[Scott_F]

I need to "pin down" the conduit in my wing ribs, and since I don't have any Proseal left, I was considering other stuff I could use for this purpose. In their FAQs, Van's recommends tank sealant or RTV for this purpose. I was discussing this with a friend who was a navy maintainer for many years, and he recalled that years ago RTV was not used on AL because of corrosive properties. A quick internet search found this article http://yarchive.net/chem/silicones.html(from 1997) discussing the corrosive properties of RTV. In a nutshell, it says that silicon sealant formulas have changed over the years, and while the current stuff does release some corrosive agents (acetic acid) during curing, on AL at least, these agents only etch the surface and increase adhesion. It does mention that RTV shouldn't be used on brass or galvanized steel.

Can someone on the list who knows about this stuff help me get a warm/fuzzy that if I squirt some RTV on my wing ribs they won't corrode? Are there any places on the plane where I absolutely should NOT use RTV?

Thanks,

[TSwezey]

You will find red (hightemp) rtv even on certified planes these days. Not 100% sure though.

[Mike S]

I have been using "Shoe Goo" for that purpose, sticks a lot better than RTV.

[hevansrv7a]

There are several which say on the pkg. they are safe for aluminum because there are so many aluminum engines. I have no expertise beyond that. I used both red and black on my airplane with full OK from my A&P/IA.

[Dan Langhout]

Dow Corning 738 should be fine - it is specifically called out by Garmin for sealing their external GPS antennas to the fuselage. Here is a quote from the data sheet for 738

A noncorrosive cure mechanism
that produces no exothermic
heat or corrosive by-products; can
be used in corrosion-sensitive
electrical and electronic
equipment (on copper and other
sensitive metals) with no adverse
effect; can be used in work areas
where sealant curing odors would
be objectionable

I personally used Permatex Ultra Black to support/glue the conduit where it passed through the holes in my wing ribs. Ultra Black is advertised by Permatex as "noncorrosive" and is used extensively on aluminum engine components in the automotive world.

I might point out though that my plane is primed 100% with AKZO epoxy primer so in my case the sealant isn't actually in contact with the aluminum anyway.

[Paul Thomas]

I did some research a few years ago and it depends on the manufacturer. Spruce had the "good" kind.

[az_gila]

...looks like a good alternative.

Only Naptha and Toluene on the MDSD list - no Acetic acid -

http://ace.infotrac.net/msdsimages/e...0inc/10321.pdf

...and it does stick well....

[AK4x4]

A&P's following Industry standard practices use Dow Corning 738 (all colors), Permatex ultra black, Permatex ultra red, and Permatex ultra copper(for exhaust ultra high Temp) routinely on aluminum surfaces with no ill effects. Hope this helps, Russ

[Scott_F]

Thanks all for the replies. I picked up some Permatex Black on the way home yesterday and put it on this morning.

-s