Abstract
Several types of macro-cells in soil, mainly in black soil, were studied in a laboratory regarding the cause of the intense corrosion which occurred on the pipeline in a volcanic soil area. Results obtained were summarized as follows: (1) In the case of a macro-cell composed of polished steel and steel covered with oxide film formed by alternate drying and wetting in soil at 75°C, the polished surface is anodic and suffers from accelerated corrosion. (2) If a differential aeration cell due to water content is superposed to the macro-cell, the corrosion rate is highly increased. (3) Effect of a macro-cell caused by the heterogeneity of soils tested is considerable but the cell is less effective than the differential aeration cell and a macro-cell caused by the oxide film.
