Prediction of multi-layer corrosion life with diffusion and distribution of chloride ions in offshore stay cable

The offshore atmosphere is characterized by high humidity and rapid airflow, with airborne pollutants transporting chloride ions and sulfur dioxide in aerosol form. These corrosion sources pose a serious threat to the durability of marine structures, particularly concrete and steel components. Existing research on stay cable corrosion has predominantly focused on individual steel wires, which fails to capture the actual performance of multi-wire cables. The interlayer shielding effect of wire bundle and diffusion of corrosive media through interstitial gaps are often neglected, leading to deviations from realistic behavior. To address this issue, a systematic investigation is conducted in this study. Based on concentration-gradient-driven transport, a chloride ion diffusion and distribution model is derived from Fick's second law and validated using COMSOL Multiphysics. Besides, previous experimental findings indicate a positive correlation between chloride ion concentration and corrosion severity. Accordingly, the MCT (corrosion amount-chloride ion concentration-time) model was established and key parameters were determined based on traditional corrosion kinetics models. Furthermore, WCT (weight loss rate-chloride ion concentration-time) and DCT (corrosion depth-chloride ion concentration-time) models were derived and validated against both accelerated corrosion and atmospheric corrosion. The results indicate that MCT model has high prediction accuracy and excellent applicability.