[RyanN]

I've never seen corrosion on the marine trailer lights around here. I also have the trick of putting Vaseline on all open electrical connections in our boats. I don't see anything special about the trailer light connections we have, but with the salt water, the lights (LED, incadescent, lifetime warranty, whatever) go out within a year no matter what, but I've only had to replace the whole wiring harness once on our boat trailer, and that was due to the wire being pinched somehow (don't remember how, but it cut all the wires). My dad had to recently replace the harness on his truck due to the "Professional Installation" by the dealership which consisted of various sized wire caps and lots of electrical tape.

My recommendation is to find a marine grade one and put Vaseline on it.