hi mike,
you can electroplate epoxy carbon composite for corrosion prevention from the saline water. better way than electroplating is to use polyurethane based gelcoat. this gives you both abrasion resistance and corrosion resistance.
for more clarificaion you can contact me at HGP@LM.CO.IN
i strongly recommend you better go for FRP. as there is design flexibility and also strength to weight ratio is very high. if you are intersted in designing a rotor blades using FRP please contact me at hgp@lm.co.in and my mobile is +91 98441 04135