Silicone and Electronics

Q. What do you get when you mix acid cure RTV and electronics inside a sealed container?
A. Worthless junk.

For use around electronics you MUST use “neutral cure” SR (silicone rubber). Most silicone RTV products, what you will find in the hardware stores, is acid cure SR. Acid cure SR exudes acetic acid as it sets. If it smells like vinegar then it’s acid cure.

Neutral cure SRs will always say “neutral cure” or similar on the container. If they do not say this or similar they will be acid cure. Do not use “acid cure” silicone rubber for electronics.

In curing,silicone reacts with moisture in the air, and this makes acetic acid (vinegar). If these fumes are not vented, they will harm things like contacts, copper and lead. Actually it chemically combines with copper to make copper acetate, which has neither good conductivity nor mechanical strength. The lead in solder will corrode into white lead, leaving behind punky tin solder joints that can’t be reflowed / repaired.

Our roof top compass enclosure was reattached by FT (after a compass direction adjustment), apparently with an acid cure silicone RTV. This left the compass sealed in an acid environment, which caused its failure after a couple of years.

When I removed the compass cover to see what may be occurring, what I found was a heavily corroded electronics board that was far beyond repair, solder joints were corroded open, small “hair” wires were eaten through, and the the copper on the circuit board was in bad shape.

This part is no longer available / manufactured. You can contact the original manufacturer but there seems to be no love lost between them and FT, so that is a dead end. Fortunately I was able to get a replacement part from a friend who did not want theirs.