Iron is a metal, an element, and it is pretty reactive. That is, it oxidizes or rusts easily. But steel is an iron-carbon alloy. It is much stronger than iron while still being fairly easy to work with and shape.

There are over 250 different stainless steel alloys

Stainless steels generally contain at least 10.5% or more chromium by weight. But chromium content can range up to 30%. It provides stainless steel with its passivity, another way of saying its corrosion resistance.

Metal passivity is when an oxide film forms on the metal's surface. This film prevents any additional chemical corrosion of the metal. Adding chromium to stainless steels forms an extremely thin but uniform, continuous, tenacious and stable chromium-rich oxide film on the surface of the steel.