A mechanic friend told me to put vaseline inbetween the rim and drum brake of a car, so that after the winter (winter tires to summer) when you pull the lugs off, the vaseline keeps the rim from corroding and bonding to the brake rotor, I have tried it and it works, no more 4x4 wood and hammer routine. I wonder if this same trick would work when you put the ladder back in next spring... maybe you could put a thin bead of silicone around the top so that the water doesnt wash the vaseline away.