What is the defining characteristic of stainless steel in terms of chromium content?

Stainless steel is defined by its significant chromium content, which is typically more than 15%. This high level of chromium is essential as it forms a protective oxide layer on the surface of the steel, effectively preventing rust and corrosion. This corrosion-resistant property is what distinguishes stainless steel from other types of steel and makes it suitable for a variety of applications, including those in harsh environments. The chromium content is key to its classification as stainless, allowing for both durability and longevity in applications ranging from kitchenware to structural components in buildings and transportation. The other ranges of chromium content mentioned do not meet the criteria for stainless steel classification, as they are insufficient to provide the necessary corrosion resistance.