Modern stainless steel contains nickel along with other elements, such as molybdenum, niobium and chromium, that help the metal resist corrosion. Nickel is merely one of the key elements that adds to the rust-resistance of steel.
When English metallurgist Harry Brearley first added chromium to low-carbon steel in the early 20th century, he discovered the metal became more stain resistant and avoided rust and corrosion at a better rate than steel alone. Over time, elements like nickel and molybdenum were added along with chromium to increase rust-resistance.
Nickel is a silvery white metal that occurs naturally in minerals, including the earth's core. Its slow oxidation rate makes it particularly resistant to corrosion, and it is very viable as a commercial manufacturing component. However, it is not the primary element that enhances the corrosion resistance of stainless steel. That honor goes to chromium.
Chromium is actually the element that gives stainless steel its greatest boost for avoiding rust and corrosion. The chromium combines with oxygen to form a thin, neatly packed layer of oxides that recover quickly if cut or scratched. In contrast, regular steel has a very loose layer that stains and flakes easily when the surface is damaged.
The three main types of stainless steel are austenitic, ferritic and martensitic. The austenitic type contains nickel along with chromium and sometimes manganese and nitrogen. Heat treatment does not harden this type of stainless steel, and it remains pliable. As a result, it is the type processed into common household kitchen appliances, such as refrigerators, ranges and dishwashers.