Abstract:

Metal`s Corrosion at the gas-liquid interface exhibits unique characteristics compared to single-phase immersion corrosion due to the high density of particles at the interface and the complex physical and chemical properties. However, it is difficult to accurately define the interface boundary and conduct localized monitoring in experimental studies, leading to a relative lack of research on corrosion at the gas-liquid interface. Based on the accurate distributing sodium chloride solution and oxygen to the interface, considering the chemical reaction mechanisms, acidic autocatalytic mechanisms, and deposit blocking mechanisms in actual corrosion processes, this study assigns different reaction rules and corresponding probabilities to particles, establish a two-dimensional cellular automaton corrosion model of the gas-liquid interface of metal-copper. By analyzing the corrosion kinetics, corrosion pit depth and product distribution in the metal-copper interfacial zone, and comparing the metal-copper with different contact angles, the results show that the metal-copper interfacial corrosion zone can be divided into a diffusion zone controlled by both chlorine and oxygen, and a thin liquid-film zone dominated by chloride ions. When the contact angle decreases from 72° to 18°, the area of the interface region increases by 3.2 times, as well as the dissolved oxygen. By comparing the corrosion in thin liquid film zone and the diffusion zone, it is found that oxygen corrosion in the diffusion zone is the primary control mechanism at the contact angle of 18°; at contact angles of 27° and 45°, chlorine corrosion in the thin liquid film zone is the primary control mechanism; while, chlorine and oxygen jointly control the corrosion process at large contact angles (63° and 72°), which reveals that the mechanism of severe corrosion in the metal-copper gas-liquid interface region is the bidirectional aggregation of liquid-phase corrosive ions and gas-phase dissolved oxygen. Simultaneously, monitoring of H⁺ concentration within the pits demonstrated that, accompanied by H⁺ generation and metal autocatalytic reactions, the metal-copper interface with a contact angle of 18° shows the largest corrosion area, the longest corrosion cycle, and most severe corrosion.

Key words: gas-liquid interface, cellular automata, interfacial corrosion, contact angle, hydrolysis