Stainless steel may have excellent corrosion resistance in many media, but in other media, due to its low chemical stability, corrosion may occur. Therefore, stainless steel cannot withstand all media. In many industrial applications, stainless steel can provide the right anti-corrosion function for modern people. According to experience, in addition to mechanical failure, the corrosion of stainless steel is mainly manifested in the following aspects: the severe corrosion of stainless steel is local corrosion (I. e. stress corrosion cracking, pitting, intergranular corrosion, corrosion fatigue and crack corrosion). The failure cases caused by local corrosion account for more than half of the failure cases. In fact, by choosing materials wisely, many variations can be avoided. According to the corrosion mechanism, metal corrosion can be divided into three types: special corrosion, chemical corrosion and electrochemical corrosion. In life and engineering, metal corrosion is mainly electrochemical corrosion. Stress corrosion cracking (SCC): A general term that refers to the interaction between stress corrosion alloys due to the propagation of severe cracks under corrosive conditions. Stress corrosion cracking is characterized by brittle fracture, but can also occur in high-ductility materials. The prerequisite for stress corrosion cracking is the presence of tensile stress (residual stress or external stress, or both) and a specific corrosive medium. The graphs are formed and spread perpendicular to the purpose of the tensile stress scale. The value of the stress that causes stress corrosion cracking is much less than the stress required to fracture the material in the absence of a corrosive medium. Cracks that pass through grains are called transgranular cracks, and cracks that propagate along grain boundaries are called intergranular cracks. When a stress corrosion crack extends to its depth (here, the stress on the cross section of the loaded material reaches its fracture stress in air), the material will behave as a normal crack (possibly a ductile material, usually through the aggregation of microscopic defects) and fracture. Therefore, the cross-section of a part that fails due to stress corrosion cracking will contain characteristic areas of stress corrosion cracking and recessed areas associated with microdefect aggregation. Pitting corrosion: Pitting corrosion refers to metal materials with high segregation, no erosion or generally slight local erosion. The common corrosion point size is less than 1.00mm, and the depth is often greater than the general aperture. The light ones have shallow pits and the heavy ones even have perforations. Intergranular corrosion: Intergranular boundaries are the boundaries of disordered dislocations between grains of different crystallographic orientations. Therefore, they are favorable areas for the segregation of various solute elements in steel or precipitation of carbide and δ-equivalent metal compounds. Therefore, in some corrosive media, the intergranular boundaries may be eroded first, but one by one. This corrosion is called intergranular corrosion. Intergranular corrosion occurs in most metals and alloys in specific corrosive media.