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I. Common corrosion sites: H₂S-H₂O corrosion occurs primarily in low-temperature, humid hydrogen sulfide environments with temperatures ≤120°C. Typical sites include the condensation and cooling system at the top of the regeneration tower in desulfurization units in refineries, which encompasses the distillation pipelines, condensation coolers, and reflux tanks. The atmospheric and vacuum tower top condensation cooling system, including phase-change areas such as the upper trays of the atmospheric tower, the tower top vapor line, and the tower top condenser. The equipment and pipelines of the absorption/desorption system in catalytic cracking units, as well as areas under sulfur-containing operating conditions where liquid water is present, such as LPG storage tanks and the aftercooler in hydrogenation units. II. Typical corrosion patterns: Uniform general corrosion: A FeS-based corrosion product film forms on the surface of carbon steel; the initial corrosion rate can exceed 10 mm/year, but it drops to around 0.3 mm/year after prolonged operation. Corrosion accelerates significantly when the equipment is shut down and restarted frequently. Hydrogen bubbling (HB): Hydrogen atoms penetrate into the defects within the steel and gather there to form hydrogen molecules; this causes the surface metal to bulge as its volume increases by 20 times, and this phenomenon can occur without any external stress. Hydrogen-induced cracking (HIC): The accumulation of hydrogen deep within steel leads to delamination and stepped cracks, with these cracks running parallel to the rolling direction of the steel; MnS inclusions significantly increase the susceptibility to cracking. Sulfide stress corrosion cracking (SSCC): Under tensile stress or residual stress, brittle cracking occurs in the high-hardness areas of steel welds and heat-affected zones; the risk of cracking increases significantly in low pH environments.