Question: My new boat has a pretty large printed circuit board mounted on the back of the primary DC power distribution panel. I’m concerned about moisture causing corrosion on the small connections and metal parts you can see in the photo. Are there any simple solutions to prevent this from happening?
Answer: Excellent question! I’ve asked some of the major manufacturers about this very thing a few times. The answer I’ve always gotten was that the boards are coated with a protectant at the factory. The actual technical term used to describe this in electro-geek land is a “conformal coating." If you do a web search for conformal coating you will learn all about the various types of coatings and different application methods.
But, to your question, the easiest and simplest way to deal with this in the field is to apply a light coating of one of my favorite products to the back of the circuit board, Boeshield T-9. My longstanding belief and faith in this product was backed up by Practical Sailor, a highly regarded publication that did a comparison test on corrosion-inhibiting sprays back in 2007. Boeshield came out as the best all-around performer in their comparisons. Other sprays they compared left a sticky, tacky coating that was probably going to work out OK, but may seem a bit messy.
As with buss bars and other things I’ve talked about here, give the board a spray with T-9 and forget it.