Study on the Influence of Soil Moisture Content and Particle Size on Corrosion Behavior of X80 Steel Under Metro Stray Current Interference

ABSTRACT Dynamic stray currents generated during subway operations induce corrosion on adjacent buried steel oil and gas pipelines, with their corrosion behavior closely tied to the surrounding soil environment. This study focused on X80 pipeline steel and investigated the influence of two typical parameters—soil moisture content (10%, 20%, and 30%) and soil particle size (100, 500, and 1000 μm) on X80 steel corrosion behavior. Electrochemical testing, corrosion weight loss analysis, and morphological analysis were employed to investigate the relationship between varying corrosion patterns and soil conditions. The results demonstrate a strong positive correlation between soil moisture content and the corrosion rate of X80 steel. The corrosion rate of X80 steel showed a strong positive correlation with soil moisture content. This trend is primarily due to the role of water in enhancing the continuity and ionic conductivity of the soil electrolyte, which facilitates charge transfer and accelerates anodic dissolution. Electrochemical analysis revealed that under high moisture conditions, the film resistance ( R f ) of corrosion products decreased significantly, indicating increased corrosion current and accelerated corrosion rates. In contrast, larger soil particle sizes inhibited corrosion progression. Coarse‐grained soil (1000 μm), characterized by higher porosity, impeded the transport of water and oxygen, leading to increased ( R f ) and charge transfer resistance. This resulted in fewer pits and shallower corrosion depths. Cathodic protection potential also significantly influences corrosion behavior. A potential of −1.2 V SCE more effectively suppresses corrosion than −1.1 V SCE . This study clarifies the interactions among dynamic stray currents, soil media, and cathodic protection, offering theoretical and practical insights for corrosion risk assessment and protection for buried pipelines near subway systems.