How does stainless steel be rusted ?

Stainless steel is well recognized by its shiny luster and its ability to resist rust, even in harsh conditions. These qualities make stainless steel perfect for applications in saltwater and other corrosive environments, so it should come as no surprise that stainless steel has a wide variety of applications.
How does stainless steel be rusted ?


The common term rust generally refers to iron oxides, formed by the oxidation of metals. Iron oxides form when oxygen and a metal, such as iron, are exposed to water. They are generally reddish-orange in color, forming unevenly on the surface of the metal. This results in the formation of pits and cavities that may reduce the performance of important components.

Iron oxides are active, and once the formation starts it will continue to grow into the surface of the material. For thin materials this can cause structural problems. When multiple parts are used, iron oxide, which has a larger mass than the original iron, can force parts in different directions and interfere with functionality or structure.

In order to combat oxidation, chromium (>10%) is added to normal carbon steel, forming what is widely known as stainless steel. This material resists corrosion by forming a passive layer of thin chrome-containing oxide when exposed to the atmosphere. This layer prevents the formation of iron oxide on the surface of the material that is exposed to air and water. If the stainless steel is scratched or damaged, the passive film quickly reforms, protecting the material from rust even when damaged.
This post is referenced from http://angiebiotech.com