A polyurethane "porch and deck" paint would be a logical choice.
Glidden makes one, Home Depot carries it, I use it...shop floor, steel French doors opening to screen porch and lanai...a counter top on the screen porch...any place where I want a hard, durable surface. The colors available are limited. I use white which yellows a bit after a couple of years but not so much that I mind it. Green mold will grow on it too if it is where it is frequently damp; if so, add some mildewcide.