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I. Core mechanisms of corrosion: The inorganic salts in crude oil are mainly sodium chloride, magnesium chloride, and calcium chloride, most of which are dissolved in the emulsified water of the crude oil. Magnesium chloride can hydrolyze at around 120°C, and calcium chloride also hydrolyzes when heated, producing hydrogen chloride (HCl) as a byproduct ； Dry HCl is non-corrosive, but it forms highly corrosive hydrochloric acid when it comes into contact with water, which can erode equipment. In the presence of naphthenic acid, sodium chloride also undergoes hydrolysis at around 300°C, further increasing the HCl content in the system and accelerating the corrosion process. II. Main factors affecting corrosion Temperature conditions: The degree of hydrolysis of calcium and magnesium salts increases significantly with rising temperature; most salts undergo hydrolysis in the middle and lower sections of atmospheric-pressure furnaces and columns, releasing large amounts of HCl. Crude oil acid value: The higher the acid value of crude oil, the more thorough the hydrolysis reaction of inorganic salts occurs, resulting in more corrosive substances being produced. Coexisting media: When H₂S is present in the system at the same time, a corrosion environment of the HCl-H₂S-H₂O type is formed; Cl⁻ destroys the FeS protective film formed on the metal surface, thereby significantly accelerating the corrosion rate. III. Typical corrosion sites and hazards: This type of corrosion mainly occurs in the condensation and cooling systems of the atmospheric and vacuum distillation units, that is, at the tops of the initial distillation tower, atmospheric distillation tower, and vacuum distillation tower, as well as in the associated pipelines and air coolers where low-temperature light oils are present. Corrosion is most severe at the gas-liquid interface, leading to uniform corrosion and pitting of the equipment; in severe cases, it can cause stress corrosion cracking in austenitic stainless steel, thereby threatening the long-term operation of the units.