Silicone Grease? corroded PCB

[Isle of Mull]

Hi,
I have my Watson sensors mounted very close to the sea (2m at high springs) and have found that the PCB inside the transmitter has corroded and failed after five years.
I have always kept the plugs covered in silicone grease or vaseline to protect them, which has worked fine, but was thinking I might smear silicone grease over the whole PCB when I replace it. There shouldn't be a problem with short circuits but I was worried it would insulate the temperature or humidity sensors.
I don't think a better screen would help as the whole unit gets a fine spray in a NW gale.
Has anyone tried this before? Any advice would be appreciated.
Thanks
John

[Gina]

Hi,
I have my Watson sensors mounted very close to the sea (2m at high springs) and have found that the PCB inside the transmitter has corroded and failed after five years.
I have always kept the plugs covered in silicone grease or vaseline to protect them, which has worked fine, but was thinking I might smear silicone grease over the whole PCB when I replace it. There shouldn't be a problem with short circuits but I was worried it would insulate the temperature or humidity sensors.
I don't think a better screen would help as the whole unit gets a fine spray in a NW gale.
Has anyone tried this before? Any advice would be appreciated.
Thanks
John

Difficult one You certainly don't want to cover the humidity sensor. I don't think the thermometer should matter though it would be slower to respond to changes in temperature. The rest of the board could certainly be covered in grease for protection. Are you sure it isn't possible to improve your screening? How about a large shield on the seaward side? Sea spray is deadly to electronics

[Isle of Mull]

Thanks Gina,
I suppose I could make some sort of screen that would stop the worst of the spray.
The old board is not completely corroded, it's just a few tracks that have gone.
I think the silicone grease should stop that.

[Charlie]

The board actually has a conformal coating from the factory, but it's not great and is often damaged by handling during final assembly. There are a number of areas on the board that will be impacted by a dielectric grease, the worst as Gina points out will be the humidity sensor.

Some components may also change value if covered with grease, as it's not completely inert. Whether or not it will be enough to affect performance remains to be seen, I guess.

You can cautiously paint it with the grease avoiding components, but honestly it's a lot of work for questionable benefit. Perhaps investing some time in building or buying a good Stevenson screen would be a better investment?

[Isle of Mull]

Hi Charlie,
Thanks for the info.
I think I may move it a little further from the sea. It will not be in as good a place for wind measurement but will give more accurate winter temperatures as the sea tends to keep the temperature up a bit when below freezing. The last one lasted a good few years so hopefully a move will solve it. I don't think any screen would completely solve the problem unless it was solid on the sea side as the spray comes in from below horizontal sometimes. I suppose a solid screen could cause measurement problems.
Thanks