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Its core mechanism can be divided into two main theoretical approaches, which together explain the entire process of crack initiation and propagation: First, the slip-dissolution (electrochemical) mechanism – a stable passivation film forms on the metal surface; under the tensile stress exerted by the gas, local plastic deformation occurs at the crack tip, and the slip steps directly destroy the passivation film, exposing fresh, active metal surfaces. The exposed fresh metal serves as the anode, while the area surrounding it with an intact passivation film functions as the cathode, thus forming a micro-corrosion cell. Since the area of the anode is much smaller than that of the cathode, the local current density is extremely high, causing continuous anodic dissolution of the metal and the progressive propagation of cracks deeper into the material. II. Mechanism of hydrogen embrittlement (hydrogen-induced cracking): Components such as hydrogen sulfide in gas react with metals to produce hydrogen atoms. These hydrogen atoms penetrate into the metal, accumulating at grain boundaries and defects, thereby reducing the metal’s toughness and causing localized embrittlement. Under the combined effect of tensile stress, microcracks preferentially initiate in the embrittled region; the crack tips continuously capture diffusing hydrogen atoms, accelerating their growth, which ultimately leads to low-stress brittle fracture of the metal.