What quality does stainless steel have that makes it resistant to corrosion?

Stainless steel is renowned for its corrosion resistance primarily due to the presence of chromium in its alloy composition. When stainless steel is exposed to oxygen, chromium reacts with the oxygen to form a thin, transparent layer of chromium oxide on the surface. This passive oxide layer acts as a protective barrier, preventing further oxidation and corrosion of the underlying metal. The robustness of this layer means that even if the surface of the stainless steel is scratched or damaged, the chromium-containing alloy has the ability to self-repair by forming new oxide in contact with air or moisture.

This protective feature is what sets stainless steel apart from many other metals, which may succumb to rust or corrosion more readily when exposed to environmental factors. The effectiveness of the chromium oxide layer is a key reason why stainless steel is commonly used in marine environments, where exposure to saltwater and humidity can accelerate the corrosion process in less resistant materials.