Les mentioned about steels that have any kind of plating on them, chrome or otherwise, and the subject of rusting. Years ago I worked in a chrome plating shop, and if metal is completely plated, it won't be subject to rust, which is erosion caused by liquids (water, for example). Scratch the plating away, just a bit, and moisture can and will attack the underlying metal. Remove plating from the cutting edge of a knife, and that steel is exposed and if moisture (like humidity) touches the steel, which it will, the metal is subject to rusting. Yes, if the knife is cleaned after use, and the bare steel is coated with a good oil, the surface will be protected from moisture and therefore rust.