I always use some form of corrosion inhibiter on all crimped joints. Silicon dielectric compound seems to work well. My personal preference is for the commercial "Anti Seize", availiable at any auto parts store. Supposed to be good for 50 years in salt water. Stick the wire into it first then crimp. Electricians also use a similar compound when dealing with aluminum wire.
In some 25 years of experience I can say that the "Anti Seize" has never failed. No joint protected by it has ever failed, whether it be electrical or mechanical.