Which of the following is a characteristic of stainless steel?

Stainless steel is known for possessing a naturally adherent oxide film, which is key to its resistance to corrosion. This oxide film forms on the surface of the stainless steel when it is exposed to oxygen and serves as a protective barrier that helps prevent further oxidation and rusting. The presence of this film is what allows stainless steel to maintain its aesthetic appearance and mechanical integrity over time, even in harsh environments.

The other characteristics mentioned do not align with the defining traits of stainless steel. While stainless steel does have some thermal conductivity, it is generally lower compared to metals like copper or aluminum. Not all stainless steels are classified as ferrous; they can contain nickel and chromium, which make them non-ferrous in certain compositions. Lastly, stainless steel typically does not require cathodic protection, which is often needed for mild steel exposed to corrosive environments, as it already has inherent corrosion-resistant properties due to its oxide film.