I used to have rats, and made their cage liner out of coroplast. Despite what people will often say, most rats tend to dribble a little when they pee, so the coroplast frequently did get peed on. As a plastic (or plastic-like material, not sure) it certainly does not deteriorate with urine. My main concerns would be the difficult to clean corners, and smell retention. Many plastic litter boxes have stuff added to the plastic to either prevent absorption of smells, or nullify them. I do not know if coroplast would have this naturally. I personally felt I could never get the rat urine smell out of the stuff I used, but rat urine is pretty potent stuff. Of course, does any litter box smell that good? Of course not.
The corners also needed to be hosed out occasionally, and then re-taped. Not a huge deal, but mind you, I did have little corner pans for the rats. I would have had to do it more frequently if they were going directly in that corner, so that is an extra step. You would also need to make sure the corner was really well done to prevent leaking.
Making the liner (which was basically a large litter box as it turned up at the edges) was a bit of a pain, but it was quite large. And once that part is done, it is done until you need a new one!

So yes, you could definitely use it, and it should not deteriorate, but it might be a little more difficult to work with and clean than a regular litter box.

Have you looked at plastic storage bins that come in different sizes – that might be better. I’ve also seen some larger size kitty litter boxes too – not just the normal size but the larger size.

This box comes in 2 sizes:

http://www.petsmart.com/cat/litter-boxes/grreat-choice-open-pan-litter-box-zid36-6670/cat-36-catid-200094?var_id=36-6670&_t=pfm%3Dcategory

I’ve only seen coroplast for guinea pig cages and it seemed to me that once they were configured into boxes they just don’t seem very sturdy even though they do fill those things full of bedding for them.

Could you cut the sides down a little on a bigger box? I had to do that even with a short box when I had my former rabbit who was getting up in age. I just used a hacksaw to cut two lines straight down, about 8 inches apart, bent the plastic back and forth until it broke, and sanded down the edges.

Look in the storage departments of places like Target and Walmart and those plastic square storage bins like the ones that go under the bed might be a good option they come in all kinds of sizes and they usually have lower sides.

I agree that under-the-bed bins make perfect litter boxes.