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Sulfides in crude oil are divided into active sulfides and inactive sulfides. Active sulfides include sulfur, hydrogen sulfide, and thiols, among others; these compounds can react directly with metals ； Inactive sulfides include thioethers, disulfides, cyclic sulfides, thiophenes, etc. These compounds cannot react directly with metals, but they can decompose at high temperatures to produce active sulfides such as sulfur and hydrogen sulfide. The corrosion of equipment by sulfides is related to temperature t. ①At t≤120℃, the sulfides do not decompose; in an anhydrous environment, there is no corrosion to the equipment ； However, when moisture is present, H2S--H2O type corrosion occurs in the light oil sections of various units in the refinery. ②At 120℃＜t≤240℃, the active sulfides in crude oil remain undecomposed, so corrosion of the equipment is not severe. ③At 240℃ < t ≤ 340℃, sulfides begin to decompose, producing H2S that starts to corrode the equipment, and the corrosion intensifies as the temperature rises. ④At 340℃ < t ≤ 400℃, H2S begins to decompose into H2 and S. The resulting FeS film acts as a barrier against further corrosion; however, in the presence of acids such as hydrochloric acid or naphthenic acid, these acids react with FeS and destroy the protective film, allowing corrosion to proceed further. ⑤420℃＜t≤430℃: High-temperature sulfur causes the fastest corrosion of the equipment. ⑥At t>480℃, the sulfides are nearly completely decomposed, and the corrosion rate decreases. ⑦t>500℃ is not within the range of sulfide corrosion; at this temperature, high-temperature oxidative corrosion occurs.