can a baby corn snake fit in a 18x18x24 enclosure? ive heard that some rat snakes are semi arboreal. is this true?

I think those dementions are fine for a baby corn. Yes some rat snakes are semi arboreal. Come to my house I can prove it. lol. You can see rat snakes climbing in the tree's in the evening time.

is it all rat snakes or just some specific ones?

I'm pretty sure all Rat Snakes in the US often climb.

cool, thanx for your help! are the requirements for rat snakes pretty similar to corn snakes?

My rat snake loves to climb so I make sure to put tall things along with those fake twigs that bend around into all shapes. Corn and rat snakes are of the same genus, so yes, the care is the same.

Baby corns often prefer smaller containers to begin with, it makes them feel more secure.

One of my corns thinks she's a boa! lol Climbs on everything she can find! Must actually put some little twigs in there for her!