Corian is much the same recipe to the old bakelite of the 50s....it's primary purpose is kitchen countertops...the different mixes do behave differently. None of them stain easily. I do not put any finish on mine. I believe that a high lustre buff job is the best you can do on it.
Here's from one of the Corian distributors site:
" A Corian ® surface that has been professionally fabricated and installed is completely sealed and non-porous, meaning it creates a durable barrier without having to be sealed. As members of the DuPont Quality Network, every Corian ® work surface we install comes with a 10-year manufacturer-backed guarantee.Mar 29, 2018 "