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1. Intergranular corrosion: Austenitic stainless steels are prone to grain precipitation and intergranular corrosion at temperatures between 450–850°C. This type of corrosion leads to a significant reduction in the mechanical properties of the material. Since intergranular corrosion occurs suddenly, it can cause sudden failure of equipment, making it a serious hazard. As the material user, an effective way to prevent intergranular corrosion is to reduce its carbon content; this can be achieved by heating the material to 1100°C for solution treatment, which not only enhances the material’s corrosion resistance but also softens it. 2. Stress corrosion cracking: A type of fracture failure in metal materials that occurs under the combined effect of tensile stress and chemical corrosion. The cracks are small; sometimes there is only one crack, but they often branch out. The sources of stress include applied stress (operational stress and thermal stress during equipment operation), residual stress (fixed residual stresses from welding, cold working, and equipment installation), as well as stress from corrosion products. For stress corrosion cracking, the stresses remaining from welding and processing are the most important. The surface condition of the material also has an impact on stress corrosion cracking. Weld thickening (resulting from repeated welding) and welding spatter often serve as indirect causes of stress corrosion cracking; therefore, these should be removed, with a smoother surface being preferable. 3. Corrosion fatigue: Corrosion fatigue occurs due to the action of corrosive agents, which reduces the fatigue resistance of metal materials. Its cross-sectional characteristics include corrosion products over large areas and roughness over smaller areas. Corrosion fatigue can involve multiple cracks, which usually originate from a deep pitting area. 4. Weld corrosion Weld corrosion is divided into heat-affected zone corrosion and kerf corrosion. Corrosion occurs in the heat-affected zones on either side of the welds in stainless steel welded parts. This corrosion is caused by the fact that during welding, the material is within a sensitive temperature range of 450–850°C, which leads to intergranular corrosion. The characteristic of edge (blade) corrosion is the preferential corrosion of metal in a very narrow area right adjacent to the weld fusion line, whereas heat-affected zone corrosion refers to the corrosion of the base metal areas that do not melt during cutting or welding, under the influence of heat; this type of corrosion occurs at a distance from the weld. Generally, the corrosion resistance of stainless steel welds is inferior to that of the base metal. 5. Pitting: Pitting is a type of corrosion that occurs in deep areas within small regions on the metal surface. In most cases, pitting is relatively minor, but cold working increases the tendency for pitting to occur. 6. Hydrogen embrittlement: Hydrogen ions in the solution are reduced to hydrogen at the cathodic region of the crack. Under stress, this hydrogen diffuses into the metal, causing it to become brittle and making it easier for the crack to propagate. As more hydrogen is generated and diffuses to the crack tip, the crack continues to extend forward.