In many industrial applications, stainless steel provides satisfactory corrosion resistance. According to the experience of use, in addition to mechanical failure, the corrosion of stainless steel is mainly manifested in: a serious form of corrosion of stainless steel is local corrosion (ie, stress corrosion cracking, pitting corrosion, intergranular corrosion, corrosion fatigue, and crevice corrosion) . The failure caused by these localized corrosion accounts for almost half of the failure cases. In fact, many failures can be avoided through reasonable selection.

Stress Corrosion Cracking (SCC): This is a general term used to refer to alloys that are exposed to stress due to the expansion of the cracks in corrosive environments. Stress corrosion cracking has a brittle fracture morphology, but it can also occur in tough materials. The necessary condition for stress corrosion cracking is the presence of tensile stress (whether residual or applied stress, or both) and the presence of specific corrosive media. The formation and expansion of the pattern are approximately perpendicular to the tensile stress direction. The stress value that causes stress corrosion cracking is much less than the stress value required for the material to break when no corrosive medium is present. Microscopically, a crack that passes through a grain is called a transgranular crack, and a crack that spreads along a grain boundary is called an intergranular crack. When stress corrosion cracking expands to a depth (here, the load-bearing material section When the stress reaches its fracture stress in air, the material breaks down as normal cracks (in ductile materials, usually through polymerization of microscopic defects). Therefore, the section of the part that fails due to stress corrosion cracking will contain characteristic areas of stress corrosion cracking and "dendrite" areas associated with micro-defective polymerization.
Spot corrosion: A form of localized corrosion that causes corrosion.

Intergranular corrosion: The grain boundary is a boundary city with dislocations of crystal grains with different crystallographic orientations. Therefore, they are favorable for the segregation of various solute elements in the steel or precipitation of metal compounds (such as carbides and δ phases). District city. Therefore, in some corrosive media, it is not surprising that the grain boundaries may be etched first. This type of corrosion is known as intergranular corrosion, and most metals and alloys may exhibit intergranular corrosion in certain corrosive media.

Crevice corrosion: This is a form of localized corrosion that may occur in the gap where the solution is stagnant or in the surface of the shield. Such gaps may be formed at the metal to metal or metal and non-metal joints, for example, where rivets, bolts, gaskets, valve seats, loose surface deposits, and marine organisms are in contact with the candle.

Total corrosion: This is a term used to describe the phenomenon of corrosion that occurs across the surface of the alloy in a relatively homogenous manner. When total corrosion occurs, the village material gradually thins due to corrosion, and even material corrosion fails. Stainless steel may exhibit general corrosion in strong acids and alkalis. The problem of failure caused by extensive corrosion is not a cause for concern, since the corrosion can usually be predicted by simple immersion tests or by referring to literature on corrosion.