The sink should be free of chips and nicks, which can expose bare iron and invite rust. Inspect a cast-iron sink thoroughly before it's installed, especially the rim, around the drain and where walls and bottom of the bowl meet. If you want the look of a cast-iron unit but with a tougher finish, consider a fireclay sink. The finish on these vitreous-china products tends to be stronger and smoother. Some manufacturers of cast-iron sinks also make fireclay units.
Most countertop fabricators can include an integral solid-surface sink as part of the job.
You can choose a sink that matches the counter, or pick one that contrasts with it. Either way, you end up with a smooth transition between the counter and sink that's easy to keep clean. Made of Corian, it offers the durability and easy care of solid surfacing in a self-rimming sink that drops into any countertop surface. But cheap finishes and thin-gauge steel mean you get what you pay for. Because the color goes all the way through, they hide nicks.