Factors affecting corrosion of grounding grid

1. Soil resistivity

Soil resistivity is an indicator of soil conductivity, which reflects the conductivity of soil media. The lower the resistivity of the soil, the more corrosive it is. Soil corrosivity is evaluated by soil resistivity in most countries. It should be noted that the resistance reducing agent not only reduces the soil resistivity, but also enhances the soil corrosivity.



2. Soil oxygen reduction potential

Soil oxygen reduction potential is a comprehensive indicator of soil redox strength. The higher the redox potential of soil is, the stronger the soil's oxidation to metal is; conversely, the weaker the corrosiveness is. The air permeability of soil directly affects the redox potential of soil. When the soil permeability is good, the soil oxygen content is high, the soil is in strong oxidation condition, and the corrosion of the grounding grid is strong. It can be seen that the degree of soil compaction also affects the corrosion life of the grounding grid when the earth is backfilled. The more compacted the backfill soil is, the longer the corrosion life of the ground grid will be.



3. Soil salt content

Soil salt content affects soil electrical conductivity. The more salt content in the soil, the stronger the electrical conductivity of the soil, the lower the soil resistivity. The reason for the difference is that strong and weak corrosion agents are different. Different kinds of salts bring different anions to soil, and different anions have different corrosion effects on metals. Chloride ion is the most corrosive anion for accelerating the anodic process of electrochemical corrosion, followed by sulfate ion, and cation has little effect on soil corrosivity.



4. Soil moisture content

The corrosion rate of the grounding grid increases with the increase of soil moisture. When the soil moisture exceeds the critical humidity, the corrosion rate of the grounding grid becomes smaller.



5. Soil oxygen content

Soil oxygen content affects the electrode potential of steel in soil, and changes the reaction speed of electrochemical anode, which directly affects the corrosion process of soil. Generally speaking, soil corrosivity is the strongest when the contents of water and oxygen change alternately, that is, when the soil is dry and wet alternately.



6. Soil temperature

The higher the soil temperature, the stronger the diffusion process and ionization process of cathode, thus accelerating the electrochemical reaction of soil corrosion. Soil temperature can affect soil resistivity, oxygen content, water content and microbial activity. Although soil temperature can change the physical and chemical properties of soil and affect soil corrosivity, soil temperature can not be used as an independent index to evaluate soil corrosivity.