Stainless steel, often called inox (French original means: inoxydable) is an alloy which include of Chrome (with minimum of Cr content of 10.5% in volume). If normal steel when exposed to oxidizing enviroment such as (humidity air, high humidity, etc.) will become rust and be corrosioned on the inner layer of material of steel. But, stainless steel is difference, when amount of Chrome is high enough, on the surface of stainless steel will form a thin layer of chromium oxide. This layer of chrome prevents processing of rust and corrosion inner of material, so, the suraface of stainless steel is always shiny.

By these features of stainless steel, nowaday, stainless steel is widely used in industrial, medical equipments and in our life. Howerver, we often missunderstand of "stainless", we think that it can not be corrosioned. But actual, the corrosion of stainless steel depends on its alloy components and the enviroment it was used in. In many cases, stainless steel is more susceptible to corrosion than normal steel. (Especially in Chlorine salt water, example: Sodium Chloride salt...)

2.Stainless steel Features:

Among of 16-18 alloying elements which were used in stainless steel, the elements of C, Ni, Cr, Mo, Mn, Si, Nb is the main influential factors, they determined the structure and the properties of the quality of the stainless steel. And Chrome is the main alloy determined to the stainless property. We can understand this property by 2 ways as follows:

1. With the content of Chrome from 12% up, steel become stainless in Oxidizing enviroment because the steel surface is protected by passive membrance of Cr2O3.
2. When Ferrite contains not less than 12.5% Cr, the electrode potential increased its equivalent phase voltage xementit (General called carbit) --> increase eletrochemical corrosion resitance --> Steel become stainless steel.