Final answer:
Chromium is the element alloyed with iron to create stainless steel, with a minimum content of 11% by mass necessary for corrosion resistance.
Step-by-step explanation:
The element that is alloyed with iron to form stainless steel is chromium. Stainless steel must contain at least 11% chromium by mass to achieve its corrosion-resistant properties. This is because chromium tends to form a protective oxide layer on the surface of the steel, which prevents further corrosion. In general, steels are alloys that may also contain varying amounts of carbon, manganese, nickel, tungsten, molybdenum, vanadium, and sometimes boron, depending on the desired properties of the steel.
Stainless steel is formed by alloying iron with chromium at a minimum 11% content by mass. Stainless steel is an alloy of iron containing a small amount of chromium. The chromium tends to collect near the surface, where it corrodes and forms a passivating oxide layer that protects the iron.