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