Stainless steel is an iron alloy with a minimum 10.5% of chromium. In stainless steel, the chromium produces a thin layer of surface oxide which prevents further corrosion of the surface, known as the passive layer. Chromium is added to make it rust resistant, and the addition of nickel improves its corrosion resistance factors in the case of frequent and aggressive usage. Increasing amounts of chromium in the stainless steel alloy creates a greater resistance to corrosion. For this reason, stainless steel plates are used in a multitude of applications, ranging from kitchen appliances to medical equipment.