Corian is not as stain resistant as it is supposed to be. It is solid surface, but still is a little porous. It is an expensive alternative that often now even costs more than real stone, but doesn't really have any advantages other than the usual integral splash if it is a counter top. As just a sink, I can't think of any reason I would want one. I colored my hair in my bathroom ONCE, because I had to scrub at it daily for weeks to get the color off. If liquid iron stains, chances are you are going to have to scrub at it constantly to have it not show.
I have a "Slate" sink in my kitchen right now (Reading the box it is actually a composite stone, home depot sells it) and that is great for resisting stains, but the dark color means I have to clean it constantly to not have water marks.
I found the metal sink I used to have easier to keep looking nice. I don't have experience with liquid iron, but I have REALLY hard water and the metal sink didn't show it, but my corian in the bathrooms does. The other plus to a metal sink is they are cheap in stock sizes. Which means you could just buy two for the price of any other sink so you could replace it after a few years if it does pick up anything.
Your best bet if you don't like replacing things is probably to get a dark color of something and live with having the water spots show.