On Mon, 13 Mar 2006 23:14:29 -0800, Roy Lewallen
wrote:

The advice to avoid acetic-acid smelling RTV because of corrosion is
passed along from person to person like an urban legend, but like an
urban legend it's just about impossible to find anyone who's actually
seen any corrosion result from its use. (A number of queries I've made
over the years has produced just one, using a very early version of RTV.)

OK, here is number 2. Hmmm wait... couldn't we use a different
ranking...

I retired from the industry and I worked for the original developer of
"Silastic RTV (TM)". My address if Midland MI if any one needs another
hint.

Yes there is an weak acid released from the regular RTVs and it
depends on the moisture in the air to aid in curing.

Is it, or will it be a problem? That is a Yes and no, or it all
depends answer.
I use plain old fashion "bathtub calk" on my antenna connections and
connectors *outside or outdoors*

The acid is not normally a problem *except* where the item is either
potted, or enclosed in a container. I would not use it on PC boards
where the foil is thin.

Outdoors I just "gob it on".

As to real corrosion:
Some years back we purchased a bunch of remote sensors that were
potted in metal boxes for use in harsh environments. They worked very
well... for about a year. One failed and who ever removed it brought
it into the shop. I decided to perform an autopsy on it. I cut the
seal, pried off the cover, and dug out the circuit board, or rather
what was left of it. The copper traces were mainly a green powder
with bigger chunks of powder around the solder joints where the wires
hung loosely.

The manufacturer of the sensors had used the wrong potting compound.
Had they used the neutral stuff (really stinks) they would have been
fine. They replace them all, they were expensive, and we had a bunch.


I've used the acetic-acid smelling stuff for decades on a variety of
metals including tinned and untinned wire, aluminum, nickel, and copper
circuit boards, and never seen a hint of corrosion. But formulations
vary widely, and my experience certainly isn't exhaustive. I'm not

There are two main producers of RTVs and the formulations are pretty
much standard. If you analyzed a tube of the stuff I doubt you could
tell which manufacturer produced it. However they have slightly
different formulations aimed at the specific use. What every you
purchase under what ever brand name most likely comes from one of
these two producers unless it says Made in China.


entirely convinced, though, that among the many formulations there
aren't others, which don't have that smell, which might be corrosive to
some materials.


People who worry about this should buy an industrial product and stay
with it, since there's a much better chance the formulation won't change
in the future without notice.

The last I knew the only difference was in the packaging.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

Roy Lewallen, W7EL

On Tue, 14 Mar 2006 19:04:48 +0000, Ian White GM3SEK
wrote:

Mike wrote:
Roy Lewallen wrote:
The advice to avoid acetic-acid smelling RTV because of corrosion is
passed along from person to person like an urban legend, but like an
urban legend it's just about impossible to find anyone who's actually
seen any corrosion result from its use. (A number of queries I've made
over the years has produced just one, using a very early version of RTV.)
I've used the acetic-acid smelling stuff for decades on a variety of
metals including tinned and untinned wire, aluminum, nickel, and
copper circuit boards, and never seen a hint of corrosion. But
formulations vary widely, and my experience certainly isn't
exhaustive. I'm not entirely convinced, though, that among the many
formulations there aren't others, which don't have that smell, which
might be corrosive to some materials.
People who worry about this should buy an industrial product and
stay with it, since there's a much better chance the formulation
won't change in the future without notice.
Roy Lewallen, W7EL

I was visiting a local SGC dealer years ago as he was troubleshooting a
brand new antenna tuner that was not working. When he opened the
plastic case, that special RTV acidic smell almost knocked us over and
all the tinned circuit board traces and exposed wiring were corroded
and black. SGC claimed they used the wrong type of RTV on a batch of
tuners that was not for electronics use.

Most likely because they closed the cases before the silicone had cured,

That outgasing from a think layer will go on for many days which would
make it impractical to use in this case.

not realising they were trapping the acetic acid vapour inside. The same
can happen in balun boxes and the like.

In this case it would also depend on how much RTV, or how thick the
layer of RTV. As I said, the outgasing will go on for quite some time
and the thicker the longer it outgases. I'd not use the acid smelling
version from either producer on PC boards.

It would be interesting to know if there have been *any* cases that
didn't also involve some kind of closed situation, or possibly a layer
that was too thick to let the vapour diffuse out.

A thin layer should cause no problem if it is given time to outgas,
but a thick layer will most likely eventually ruin the PC board.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

Roger wrote:
I was visiting a local SGC dealer years ago as he was troubleshooting a
brand new antenna tuner that was not working. When he opened the
plastic case, that special RTV acidic smell almost knocked us over and
all the tinned circuit board traces and exposed wiring were corroded
and black. SGC claimed they used the wrong type of RTV on a batch of
tuners that was not for electronics use.

Most likely because they closed the cases before the silicone had cured,

That outgasing from a think layer will go on for many days which would
make it impractical to use in this case.

not realising they were trapping the acetic acid vapour inside. The same
can happen in balun boxes and the like.

In this case it would also depend on how much RTV, or how thick the
layer of RTV. As I said, the outgasing will go on for quite some time
and the thicker the longer it outgases. I'd not use the acid smelling
version from either producer on PC boards.

It would be interesting to know if there have been *any* cases that
didn't also involve some kind of closed situation, or possibly a layer
that was too thick to let the vapour diffuse out.

A thin layer should cause no problem if it is given time to outgas,
but a thick layer will most likely eventually ruin the PC board.

Agreed; but that isn't really the fault of the silicone material. It's
more like "misuse".

But why do we use silicone for coax/antenna sealing anyway? Anything for
which you might use silicone could probably be done a lot better using
hot-melt glue.

Ordinary hot-melt glue (amorphous polypropylene) has good RF properties,
is non-corrosive, is very sticky, seals very well to metals and
plastics, is flexible, has no problems about being used in thick layers,
sets in minutes rather than hours, has at least as good weathering
properties as silicone, can be removed by cutting, peeling or melting,
and is very economical.

You can often use it in the backyard without electrical power, because a
typical glue gun gives up to 5 minutes working time after having been
unplugged.

There's more information in the archives of this group, thanks to Barry
Ornitz, WA4VZQ.


--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

On Mon, 13 Mar 2006 18:59:34 -0500, "Robert11"
wrote:

Hello:

Is it safe to use the typical GE RTV silicones against a Polyethylene (PE)
coax outer jacket ?

I know the RTV's use some type of acid (acetic ?) to cure the stuff, and I
was wondering if
anyone might have any first hand experience if there is any kind of
interaction with a coax outer jacket ?

Thanks,
Bob

Although Bob isn't asking about sealing connectors, this thread has
drifted that way.

If this is indeed his need, then I offer my method. I use
Plymouth-Bishop No. 122 rubber tape followed by an overwrap of a good
quality vinyl tape.

http://www.plymouthbishop.com/

If memory serves, I bought the 122 at Home Depot, although their web
site doesn't show that they carry it anymore. An electrical supply
house would likely be a source.

Scotch® Self-Fusing Silicone Rubber Electrical Tape 70
1 in x 30 ft

This is a high-temperature, arc-and track-resistant tape composed of
self-fusing, inorganic silicone rubber with an easy-tear and easy-strip liner.
Packed 1 per box, 10 per carton with 50 per case.

In article ,
Wes Stewart wrote:

If this is indeed his need, then I offer my method. I use
Plymouth-Bishop No. 122 rubber tape followed by an overwrap of a good
quality vinyl tape.

http://www.plymouthbishop.com/

If memory serves, I bought the 122 at Home Depot, although their web
site doesn't show that they carry it anymore. An electrical supply
house would likely be a source.

My local Home Depot had it in stock as of last week... I bought a
couple of rolls, and they had plenty more.

Their web site seems to show only a fraction of what they have in the
stores.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!