Grey Correlation Analysis of Grounding Grid Materials Corroded in Soil Extract Solutions

Significant factors which influence the corrosion rates of red copper and hot-dip galvanized steel in soil extract solution were obtained by analyzing the influence degrees of pH and common anions in the soil with grey correlation method. Corrosion mechanism of grounding grid materials corroded by significant factors was studied by open circuit potential measurement, EIS and polarization curve test. The results showed that Cl- and pH were the significant factors influencing the corrosion rates of red copper and hot-dip galvanized steel. When the concentration of Cl- was 0.01mol/L or 0.1 mol/L, the corrosion rate of red copper was influenced by the state of charge on the surface. When the concentration of Cl- was 0.3 mol/L, the charge transfer resistance reduced due to Cl-, the influence degree of pH on red copper was not significant any more. Hot-dip galvanized steel corroded severely in both acidic and alkaline solutions containning Cl-, pitting was caused by the accumulation of Cl- in Zn coating, and Cl- congested easily in coating in alkaline environment.