Water collects in bottom of refrigerator

[momto4girls]

just got back from our first camping trip. The fridge worked great, but frost builds up and melts in the freezer--dripping water into the bottom of the fridge. I wondered why the racks had rust on them. There is also rust on the outside bottom of the fridge. Is this normal par for the course? Before we left the campground, I emptied the refrigerator and put a folded towel in the bottom of the fridge to catch the thawing frost. It was wet but not soaked when we got home.