C&C Alternatives WOOD CAGE treatment

Some sort of marine varnish might work, but the chemical in the urine might make it deteriorate quicker. And I can't imagine that coroplast is much more expensive, if any, than the sealer you'd need to use. You can usually find old political signs around -- they're made of coroplast, and can be taped together from the back side.

You can buy coroplast from Home Depot for $13. Not sure how much those sprays would cost you.

https://www.homedepot.com/p/COROSPL...-in-Twinwall-Plastic-Sheet-COR-3672/202771364

Thats incrediblt expensive. My cage is 6ft by 3ft soooo i would need 3 sheets at 16$ each is almost 50$ ehere i can just buy a sprsy

You'd need one sheet, not three. Most sheets are 4 ft by 8 ft. And if you can find a Sabic Polymershapes store close to you, they're really cheap. There's a store locator on this site: (broken link removed).

Why would you need three sheet if you're just going to line the floor? The sheet is 3x6 ft.

If you're going to make a tray, you only need one 4x8 ft. sheet.
Home Depot also carries 4x8 ft sheet for $15
https://www.homedepot.com/p/Coropla...te-Corrugated-Plastic-Sheet-CP4896S/205351385

Sabic Polymershapes might be cheaper if you have them in your area.

Edit to add:
One thing to think about is that the spray paint is toxic. If you choose to do it, you would need to air it out for at least a week before putting your guinea pigs back in the cage. I'm not sure if spray paint is a good option.