QUESTION

i have porcelain tile on my screen porch, in damp weather and rain i get alot of standing water. can it be sealed to prevent this.

ANSWER

ANSWER -  Industry standards require tile floor surfaces in areas that are subject to being wet must have a slope to drain of 1/4 inch per foot.   So if  water is getting into your screed porch and the porcelain tile is not sloped so the water can drain away there is nothing you can do about it.  Applying a sealer will cause the water to bead up, but will not help it drain.

So the only option you have is to try to keep the water from getting into the screed off porch and puddling up on the porcelain tile.