Stainlessness of stainless steel was discovered by accident. In 1913, English metallurgist Harry Brearly was working to produce steel that is resistant to erosion caused by high temperatures. He discovered that adding chromium to steel gives it new abilities; among them a resistance to stains.
When a minimum of 10-12% of chromium was added to carbon steel, the chrome joined with oxygen would form a thin transparent layer over the surface of steel stopping further oxidation. This tight layer is self-repairing when scratches or other injuries to stainless steel occur.
Today’s stainless steel has many components: chromium, nickel, manganese, aluminum, carbon, columbium, copper, and titanium. Each component contributes to non-corrosion and stain resistance features of stainless steel.