In many industrial applications, stainless steel can provide satisfactory corrosion resistance. According to the experience of use, in addition to mechanical failure, the corrosion of stainless steel is mainly manifested as follows: a serious form of corrosion of stainless steel is partial corrosion (ie stress corrosion cracking, pitting corrosion, intergranular corrosion, corrosion fatigue and crevice corrosion) . The failure cases caused by these partial corrosion accounted for almost more than half of the failure cases. In fact, many failure accidents can be prevented by reasonable selection of materials.
Stress Corrosion Cracking [SCC]: A general term for the mutual failure of stressed alloys in a corrosive environment due to the growth of strong lines. Stress corrosion cracking has a brittle fracture morphology, but it can also occur in highly ductile materials. The necessary conditions for stress corrosion cracking to occur are the presence of tensile stress (whether residual stress or applied stress, or both) and a specific corrosive medium. The formation and expansion of the profile is approximately perpendicular to the direction of the tensile stress. The stress value that causes stress corrosion cracking is much smaller than the stress value required to fracture the material in the absence of corrosive media. Microscopically, the cracks that pass through the grains are called transgranular cracks, and the cracks that expand along the grain boundaries are called intergranular cracks. the stress reaches its breaking stress in air], then the material breaks as a normal crack (in ductile materials, usually by the aggregation of microscopic defects). Thus, a section of a part that fails due to stress corrosion cracking will contain characteristic areas of stress corrosion cracking as well as "dimples" regions associated with aggregates of microdefects.
Pitting corrosion: is a form of partial corrosion that causes corrosion.
Intergranular corrosion: The grain boundaries are the boundaries of disordered interlacing between grains with different crystallographic orientations. Therefore, they are favorable for the segregation of various solute elements or the precipitation of metal compounds (such as carbides and delta phases) in steel. District city. Therefore, in some corrosive media, it is not surprising that grain boundaries may be etched first. This type of corrosion is called intergranular corrosion, and most metals and alloys may exhibit intergranular corrosion in certain corrosive media.
Crevice corrosion: is a form of partial corrosion that can occur in crevices where the solution is stagnant or in the surface of a shield. Such gaps can be formed at metal-to-metal or metal-to-non-metal joints, for example, at rivets, bolts, gaskets, valve seats, loose skin deposits, and marine life candles.
General Corrosion: A term used to describe the phenomenon of corrosion that occurs in a relatively uniform manner over the entire surface of the alloy. When general corrosion occurs, the village material gradually becomes thinner due to corrosion, and even the material fails due to corrosion. Stainless steel may exhibit general corrosion in strong acids and alkalis. Failure problems due to general corrosion are less of a concern, as this corrosion can usually be predicted by a simple immersion test or by reviewing the literature on corrosion.
