Surface chemistry of cooking
Stainless steel is considered stainless because it has at least 11% chromium by mass. Chromium is a relatively inert metal and does not rust or react as easily as plain carbon steel. This is what makes it an exceptional material for cooking. It is also fairly inexpensive, but does not have a very high thermal conductivity. From a surface standpoint, this is because of the thin layer of chromium oxide that is formed on the surface. This thin layer protects the metal from rusting or corroding. While it is protective, the oxide layer is not very conductive, which makes cooking food less efficient than it could be. For most cooking applications, high thermal conductivity is desirable to create an evenly heated surface on which to cook. In this way, stainless steel is usually not considered high-grade cookware.
Ferrochrome
Stainless steel depends on chromium for its appearance and its resistance to corrosion. The average chrome content in stainless steel is approximately 18%. It is also used when it is desired to add chromium to carbon steel. FeCr from Southern Africa, known as "charge chrome" and produced from a Cr containing ore with a low carbon content, is most commonly used in stainless steel production. Alternatively, high carbon FeCr produced from high grade ore found in Kazakhstan (among other places) is more commonly used in specialist applications such as engineering steels where a high Cr to Fe ratio and minimum levels of other elements such as sulfur, phosphorus and titanium are important and production of finished metals takes place in small electric arc furnaces compared to large scale blast furnaces.