High-alloy steels such as 13 chrome steel and 18-8 chrome-nickel steel represent performance. From a metallographic point of view, because stainless steel contains chromium, a very thin chromium film is formed on the surface. This film isolates the oxygen from the steel and acts as a corrosion resistance. The surface properties of stainless steel are also reflected here. In order to maintain the inherent corrosion resistance of stainless steel, steel must contain more than 12% chromium.

Used in occasions where welding is required. The lower carbon content minimizes the precipitation of carbides in the heat-affected zone near the weld, and the precipitation of carbides may cause stainless steel to produce intergranular corrosion (welding erosion) in certain environments. Because it will damage the surface of stainless steel and adhere to iron powder to form causes of rust.

In our daily life, we sometimes find that the stainless steel of some flagpoles, shelters, light boxes and other facilities on the street is pickled with obvious rust. Since the stainless steel is passivated, why does it still rust? In these situations, there are two causes of rust. One is the low content of chromium in the material, which is inferior stainless steel. Second, it is not stainless steel at all, but uses electroplating to deceive users.

It is understood that many decorative materials now use this electroplating process to process their appearance. Because the material is ordinary steel, when the electroplating layer is peeled off, it will naturally rust.

Stainless steel has the ability to resist atmospheric oxidation---that is, rust resistance, and it also has the ability to resist corrosion in media containing acid, alkali, and salt---that is, corrosion resistance. However, the size of its anti-corrosion ability varies with the chemical composition of the steel itself, the state of mutual addition, the conditions of use and the type of environmental media.