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I. Main corrosion sites: High-temperature H₂ corrosion in the petrochemical industry occurs primarily in the high-temperature, hydrogen-exposed areas of hydrogenation units. Typical locations include hydrogenation reactors, heat exchangers for reaction products, associated process pipelines, as well as the high-temperature, hydrogen-exposed core equipment and pipelines in units such as residue hydrogenation. II. Typical corrosion forms: High-temperature hydrogen corrosion occurs in two forms: one is surface decarburization, and the other is internal decarburization. Hydrogen atoms penetrate into steel and react with unstable carbides to form methane, which accumulates between the grains and causes intergranular fractures, leading to an irreversible decline in the strength and toughness of the steel – a phenomenon known as permanent embrittlement. High-temperature H₂+H₂S synergistic corrosion: In a hydrogen-rich environment at temperatures of 300–420°C, H₂ undermines the integrity of sulfide scale layers, accelerating the erosion of steel by H₂S. The corrosion pattern is primarily uniform corrosion, accompanied by combined damage from hydrogen embrittlement and hydrogen corrosion. Other forms of hydrogen-induced damage include hydrogen bubbling and hydrogen embrittlement. Hydrogen embrittlement can be partially reversed once the source of hydrogen is removed, whereas hydrogen bubbling occurs when hydrogen molecules accumulate in the gaps within the steel, creating high pressure that leads to local bulging or even cracking.