Research On Corrosion Of Grounding Grid Materials In Typical Soil In China

For grid system, the grounding grid is mainly responsible for discharge, which has played a great role in the protection of power system. Synthesizes the conductivity, thermal conductivity, machinability, application property and economy of grounding grid, grounding grid generally choose Q235 carbon steel in China, but the biggest weakness of Q235 is the poor corrosion resistance in solid. In order to achieve satisfy the requirement of discharge, chemical resistance-reducing agent is added to solid, the addition of Cl^- and SO₄^2- will increase the corrosion of grounding grid. To ensure the system operating regularly, the grounding grid must be checked frequently, the excavation process has huge amount of work, high difficulty. Not only affect the running of grid system, but also it's costly. So researching the corrosion behavior of grounding grid in solid has great significance for the material selection and the determination of maintenance period.The corrosion behaviors of Q235, hot dip galvanized steel and sherardizing steel were studied by the buried tests in Dagang, Yingtan, Golmud and Karamay. Buried test time is 2 years divided into four periods. The soil physico-chemical properties of these four stations have been analyzed. Combining the corrosion rate and soil physico-chemical properties to analysis the key factors affected the solid corrosion. The corrosion products have been tested by XRD, the relationship between the soil physico-chemical properties and the content of main corrosion products has been studied. By the electrochemical test, the resistance of corrosion products has been analyzed.The results were been shown as follows:The corrosion grade of Dagang, Yingtan, Golmud and Karamay are serious, medium, lightest and light.Q235 is uniform corrosion in Dagang and Yingtan, it is pockmark corrosion in Golmud and Karamay. The corrosion potential turns negative with the buried time, which shows the corrosion resistance of Q235 reduced.The key factors affected the solid corrosion of Dagang are moisture content and Cl^-content; which of Yingtan are moisture content and pH; which of Golmud are air permeability, porosity, xygen content and pH; which of Karamay is moisture content.The corrosion rates of hot dip galvanized steel and sherardizing steel are lower than Q235 obviously. The corrosion resistance of sherardizing steel is superior to hot dip galvanized in Dagang seashore saline soil, Golmud saline soil and Karamay brown desert soil. In Yingtan acid red soil, The corrosion resistance of sherardizing steel and hot dip galvanized are close.For hot dip galvanized steel and sherardizing steel, the Soil chemical properties——the content of Cl^- and SO₄^2- is the key factors that affect corrosion products composition and relative content. The mainly corrosion products of hot dip galvanized steel and sherardizing steel were Zn₅?OH?₈Cl₂·H₂O and NaZn₄?SO4??OH?₆Cl·6H₂O in basic soil. With the content of Cl^- increasing, content of Zn₅?OH?₈Cl₂·H₂O increasing as well, so Cl" will accelerate the generation of Zn₅?OH?₈Cl₂·H₂O. In Yingtan acid red soil, The mainly corrosion products of hot dip galvanized steel and sherardizing steel was Zn₅?CO₃?₂?OH?₆, and the reason is that the acid red soil lack Cl^- and SO₄^2-.