**6. Conclusions**

The spatial diffusion model of corrosion factors was built using the ML method based on the test results of concentrations of corrosion factors at various positions in the space of the cable system and Fick's second law. The relevant empirical formulae were presented, and the accuracy of the theoretical model was verified using multiple nonlinear regression analysis methods, taking into account the effect of various parameters on the diffusion coefficient of corrosion factors and the concentration of surface corrosion factors. The specific conclusions are as follows:


**Author Contributions:** Conceptualization, S.L., G.Y., W.W. and X.Y.; methodology, G.Y.,W.W. and X.Y.; software, S.L., X.Y. and X.H.; validation, S.L., X.H. and C.R.; formal analysis, S.L., G.Y., W.W., X.Y., C.R. and H.L.; investigation, G.Y., W.W. and X.Y.; resources, X.H., C.R. and H.L.; data curation, S.L., X.H., C.R. and H.L.; writing—original draft preparation, S.L., G.Y., W.W., X.Y., X.H. and C.R.; writing—review and editing, S.L. and G.Y.; visualization, X.Y., X.H., C.R. and H.L.; supervision, S.L. and W.W. All authors have read and agreed to the published version of the manuscript.

**Funding:** The National Natural Science Foundation of China (Grant No. 52178273), the Natural Science Foundation of Chongqing (Grant No. cstc2021jcyj-msxmX1159), the Chongqing Talent Plan Project (Grant No. cstc2022ycjh-bgzxm0124), the Open Fund of State Key Laboratory of Mountain Bridge and Tunnel Engineering (Grant No. SKLBT-YF2105), the Team Building Project for Graduate Tutors in Chongqing (Grant No. JDDSTD2022003), the Joint Training Base Construction Project for Graduate Students in Chongqing (Grant No. JDLHPYJD2020004) and Research and Innovation Program for Graduate Students in Chongqing (Grant No. CYS22392 and 2022S0007).

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author.

**Conflicts of Interest:** The authors declare no conflict of interest.
