Thanks for sharing your experience Harold!

I'd also add that if the boards are just dirty or dusty, you can just remove all batteries, then wash with a toothbrush and water. Air dry (or use compressed air which speeds things up greatly) and then spot clean areas that need solvent with isopropanol as Harold mentioned. Also if you don't have access to conformal coating, you can also use a non-conductive clear lacquer.  The conformal coating covers all the components and prevents short circuits due to conductive water (ie: salt water) or other contaminants. However if you do use a conformal coating, make sure all cables are connected first and the device is in the exact state that it will be deployed in. Also don't conformal coat the battery connectors since you'll want to change out batteries periodically.

Hi Akiba, 
thanks for your this great advice! I used the conformal coating on parts
of the PCB with exposed metal but was has hesitent using it on the "backside" with 
 all the resistors and transistors. Also what about the "back" of the microfon. Might this side be coated?
Do you have any experience with coatings @alex_rogers 

Greetings,
Robin  

Cleaning the water damaged audiomoth boards is in full swing:

Left before, right after cleaning