| Corrosion of underground water pipe lines under the control of the Seoul City Administration are chiefly attributed to stray currents, soil, water and bacteria, according to this study on the corrosions of the water pipe lines in Seoul City. The stray current corrosion due to leakage current from the street-car rails was most severe in the area near a substation and it is considered possible to determine the location and capacity of a drainer of such current by measuring the potential difference between the pipe and ground involved. The soil corrosivity is dependent upon soil characteristics such as resistivity, pH value and corrosive substance, and a contact between heterogeneous soils accelerates the corrosive effect because of a long cell formed owing to the difference in soil texture. The concentration of hydrogen ions and oxygen dissolved, contents of sulfate and chlorine ions, turbidity and evaporation residues in raw and purified water are the factors exerting corrosive effect, although such factors vary by the location of a water supply basin and by season. The microbic corrosion is basically an electrochemical action in the last analysis, although its degree varies according to the kinds of bacteria, and it is considered that this type of corrosion can be prevented by a cathodic protection technique. |
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