Nope. Any crack or gap in such a thick coating will just allow the water to settle in between layers and rust out faster. You want the water to evaporate or disappear. A refinished fuel tank and perhaps an aluminum shield such as is on the original rad fan may be a better solution if you're worried about it.
Clean thoroughly. Prime with metal etch primer. Multiple coats of an epoxy topcoat. Or...clean thoroughly, prime with metal etch, black truck bed liner (which is a tough, thick epoxy paint anyway). Don't park outside for years on end under the trees in the grass will do more to preserve the tank.
Just my $.02.
