Types of Stainless Steel Corrosion – Corrosion Resistance of Stainless Steel Series

– Stress corrosion cracking: is a general term that refers to the mutual failure of stressed alloys due to the expansion of severe cracks in corrosive environments. Stress corrosion cracking has brittle fracture morphology, but it may also occur in materials with high toughness. The necessary condition for stress corrosion cracking is the existence of tensile stress (residual stress, applied stress, or both) and a specific corrosion medium. The formation and expansion of the pattern are roughly perpendicular to the direction of tensile stress. The stress value causing stress corrosion cracking is much smaller than the stress value required for material fracture in the absence of a corrosive medium. On the micro level, the crack passing through the grain is called a transgranular crack, and the crack extending along the grain boundary is called an intergranular crack. When the stress corrosion crack extends to a depth, the material will be broken according to the normal crack (in ductile materials, it is usually through the polymerization of micro defects). Therefore, the cross-section of parts that fail due to stress corrosion cracking will contain the characteristic area of stress corrosion cracking and the area associated with the polymerization of micro defects.

– Pitting corrosion: is a form of local corrosion that leads to corrosion.

– Intergranular corrosion: intergranular boundaries are the boundaries of disordered dislocation between grains with different crystallographic orientations. Therefore, they are the segregation of various solute elements or metal compounds in a favorable area for precipitation. It is not surprising that in some corrosive media, the intergranular boundary may be corroded first. This type of corrosion is called intergranular corrosion, and most metals and alloys may exhibit intergranular corrosion in specific corrosive media.

– Crevice corrosion: it is a form of local corrosion, which may occur in the crevice where the solution stagnates or on the shielded surface. Such a gap can be formed at the junction of metal and metal or metal and non-metal, for example, at the junction with rivets, bolts, gaskets, valve seats, loose surface sediments, and marine organisms.

– General corrosion: a term used to describe corrosion that occurs on the entire alloy surface in a relatively uniform manner. When comprehensive corrosion occurs, the village material gradually becomes thinner due to corrosion, and even the material corrosion failure. Stainless steel may show overall corrosion in strong acid and alkali. The failure caused by total corrosion is not very worrying, because this kind of corrosion can usually be predicted by a simple immersion test or by consulting the literature on corrosion.