I wish to protect circuitry which will be subject to sea spray. Silicone mastic gives off acid when it cures and corrodes the circuit. What could I use please?

Thanks

 

How complex do you want? Some of the silicones mastics do not release acetic acid on curing. GE silicone II (as I remember) is virtually oderless. There are also liquid rubber products (like the colored dip material) that cure by solvent evaporation. Many polyurethanes are moisture curing, like gorilla glue and automotive windshield sealant. The former may foam to much, but the automotive product does not. Two-part polyurethanes may also work.

If you are in the USA, try the McMaster-Carr catalog (http://www.mcmaster.com) for some more ideas.

John

 

There are epoxy-like conformal coatings you can use, as well as the option of completely potting the circuit in Epoxy.

If you have an amount of heat to dissipate, connect a large heatsink to the transistors, and pot the circuit "upside down", so that when turned right side up, only anodized/protected heat sink fins are visible.

Potting is Expensive and not easy to maintain for larger circuits, though. Conformal coatings come either in small spray-paint type cans, or as a 2 part liquids, which are mixed and applied with an air powered paint gun with a large (5mm+) nozzle.

--ETA: Just thought again on "Immersed" verses "sea spray". Epoxy potting is the only DIY method with excellent success resluts that I can think of. If an enclosure is built water tight, but exceeds depth limit, water will get in. In my experience, most "watertight enclosures" are Much Better at keeping water in instead of keeping it out.

 

Why not just buy an IP66 or above rated enclosure (box)?

http://www.aquatext.com/tables/ip_ratings.htm

 

What voltage potential are we talking about? A 3.5V microprocessor will be a lot easier than a 6KV submersible pump.

 

Dip the board in melted wax. Perhaps twice to give it an uniform layer.

Or, depending on size, wrap it in sponge to conceal sharp edges and put it inside a condom, or two. Let the wires come out trough a knot, or nylon tie.
Miguel