Just to dredge up an old thread and maybe help someone, I have worked and built a lot on computers for fishing boats, ships and super yachts. To protect computers from corrosion you can use a vapour phase corrosion inhibitor. A VPCI.
These are available in many different forms, from spray powder, spray liquid, to conformal coatings, gels, and devices that will for years emit a corrosion inhibitor into a confined space.
We have a great small australian company that makes VPCIs at low cost. Called Senson.
http://www.sensongroup.com/senson-tek/home (needs flash)
I use the marine guard Gel on all exposed connectors, internal and external
I use a vapaguard pad inside enclosures.
I use the Senson Electroguard Conformal Coating and paint all boards with it. Very, very good product, just don’t paint edge connectors
All the above have integrated VPCIs.
Through this combination I have made PCs that last for 5 years + in extremely poor environments (liquid salt spray in the air every day, from waves at sea!)
I use the same products to repair circuits and connectors already damaged. I clean them thoroughly then apply the products. If they still work, they then keep working, even with amazing amounts of historical corrosion! You stop the damage in its tracks.
If Australia is a bit far away from you, another global leader on VPCIs is US based Cortec corporation. They have similar products, but not quite as good IMO.
Cheers, and may your ships never sink on the great barrier reef due to corrosion from not using Senson corrosion protection products in your GPS mapping navigation computer