I've seen it happen on some.
You shouldn't need to replace the antenna unless there is severe damage, doesn't look like it in the photo.
Water can run down the whip and get into the "cone" part of the base. Over time it'll cause some corrosion. It's one of the reason why I always recommend inspecting the antennas frequently and doing some preventative maintenance.
What I've done when this has happened with any of mine is to disassemble as much as you can. Remove the set screw(s) all the way. Pull the whip out. Using some fine sand paper, file, steel wool, etc. clean off any visible corrosion, but don't go overboard and take plating off any of the surfaces. Make sure the set screw is clean, especially the point where it would engage the whip. Clean out the inside of the cone, you might need to be a bit creative, but you don't need to do much, just clear it out as best as you can.
When you reassemble it, the set screw threads will make good contact with the cone. Tighten it down enough that it makes good solid contact with the whip.
That's usually enough to cure any issues. If you are really concerned about this, you can add a bit of silicone sealer to the whip/cone mating area after reassembly. I've never needed that with any of mine, and I spend 95% of my time within a few miles of the ocean.
