Study on the influence of temperature and water content on soil resistivity and the corrosion behavior of Q235 steel in Tibet

Purpose In recent years, the rapid expansion of China’s State Grid has faced considerable challenges in Tibet, where unique environment − including high elevation, widespread permafrost and pronounced temperature fluctuations. However, the laws and the underlying mechanisms by which temperature and water content influence soil resistivity and corrosion behavior in Tibetan power grid infrastructure remained poorly understood. Design/methodology/approach Based on actual soil samples obtained from service conditions in Tibet, and through laboratory experiments, the soil resistivity, macroscopic corrosion morphology, corrosion rate and corrosion products were analyzed, investigating the laws and the mechanisms underlying soil conductivity and corrosivity under varying temperature and water content conditions. Findings Soil resistivity increased as temperature decreased. When the temperature dropped from above 0°C to below 0°C, resistivity rose significantly, with the magnitude of increase being more pronounced at lower water contents. Specifically, when temperature decreased from 20°C to −18°C, resistivity increased by a factor of 258.7 at 5% water content and by a factor of 490.7 at 20% water content. The corrosion rate of Q235 steel exhibited a positive correlation with both soil temperature and water content. When the temperature dropped below 0°C, the corrosion rate of Q235 steel remained below 0.01 mm/y. Temperature had no significant effect on the generation of corrosion products (FeOOH and Fe2O3). The underlying mechanisms by which temperature and water content influence soil resistivity were analyzed. Originality/value Based on actual soil samples obtained from service conditions in Tibet, a mechanism governing the influence of temperature and water content on soil resistivity was proposed.