One of the topics that always comes to the surface when discussing steel hulls is rust. Yes, rust can be and is a problem with steel hulled boats that were not properly painted and or not properly maintained.
You'll also find that most of the negative comments regarding steel hulled boats and rust come from those not truly in the know. To give you some credible information on the topic of rust and steel hulled boats here's a quote from a designer of serious ocean going boats, Tad Roberts (Note: He's also a well respected member here on TF):
"Once upon a time it was a terminal problem. Today with modern coatings, if properly cleaned, primed, and applied, there is no problem. Rust only appears where the coating has failed. All wear points like rub rails, cleats & bitts, hawse pipes, cabin edges, etc. should be stainless steel and radiused."