Stainless steel is a kind of high-alloy steel that can resist corrosion in air or chemical corrosion medium. It has beautiful surface and good corrosion resistance. It does not need to go through surface treatment such as plating color, but plays the inherent surface performance of stainless steel. It is used in many aspects of steel. It is usually called stainless steel. The representative properties are 13 chromium steel, 18 chromium nickel steel and other high alloy steel. From the perspective of metallography, because stainless steel contains chromium, a very thin chromium film is formed on the surface, which is isolated from the oxygen invading the steel and plays a role of corrosion resistance. In order to maintain the inherent corrosion resistance of stainless steel, the steel must contain more than 12% chromium.