Underground metal pipelines are severely corroded in weakly leached soils such as coasal solonchak, salinized fluvo-aquic soil and yellow fluvo-aquic soil. Within 10 years they cast be perforated at a number of points, with a maximum rate of hole corrosion of 1.5 mm/yr. The number of perforated holes is associated with such factors as the resistivity, salt content, and chloride cgntent of soil, of which the chloride content is the most important. In moderately leached soils such as Shajiang soil, brown earth, dark loessial soil, cinnamon soil and castanozam,the pipelines are corroded less severely, and commonly no perforation will take place wirhin 10 yssrs; while in strongly leached soils such as paddy soils with Fe-humic coatings, paddy soils developed on red earth and lateritic red earth, as well as lateritic red earths, thry are corroded most slightly, with a maximum rate of hole corrosion of 0.01 mm/yr. Yet, in areas of boggy paddy soil under anaerobic conditions in South China, the maaimum rate of hole corrosioa may be up to 0.5 mm/yr, due to a corrosion by microbes.