Impact assessment of dynamic soil moisture on long-term corrosion behavior of buried steel pipelines using an integrated computational framework

Corrosion of buried steel pipelines is strongly governed by spatiotemporal variability of soil moisture driven by climatic fluctuations. This study investigates the impact of dynamic soil moisture conditions on steel pipelines using an integrated computational framework that incorporates climate-driven surface boundary conditions and moisture-dependent electrochemical kinetics. The experimentally observed non-monotonic dependence of corrosion rate on soil saturation was first simulated using the proposed framework, demonstrating that the trend is governed by the competition between oxygen availability and wetted electrochemically active areas across different moisture conditions. The same framework was further validated using data from a controlled 135-day corrosion experiment, confirming its ability to capture the transient corrosion response with moisture variation. To make long-term simulations computationally practical, a Thornthwaite Moisture Index (TMI)-based climatic boundary was introduced as an approximation. The simulated moisture and corrosion responses under TMI were compared with those obtained using a high-resolution physically driven climate boundary, showing that the approximation method captured major features of soil moisture variation and the corresponding corrosion response. On this basis, the framework was used for long-term scenario analyses. The results indicate that corrosion varies substantially with burial depth and soil texture owing to the interaction between seasonal moisture cycles and corrosion product layer formation. In addition, sensitivity analysis shows that neglecting spatiotemporal moisture fluctuations may lead to non-conservative estimation of long-term corrosion severity. Collectively, the study findings indicate the importance of dynamic soil moisture in assessing corrosion behavior of steel pipelines and its implications for pipeline integrity evaluation.